1941 Onderstepoort Journal of Veterinary Science and Animal Industry, Volume 16, 1941
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Item Subject index(Pretoria : The Government Printer, 1941) Anonymous; Du Toit, P.J.Item Author index(Pretoria : The Government Printer, 1941) Anonymous; Du Toit, P.J.Item Studies on the basic characteristics of South African Merino wool IV. Scaliness(Pretoria : The Government Printer, 1941) Bosman, V.; Van Wyk, C.M.; Du Toit, P.J.A study of the scaliness of South African Merino wool samples showed that the percentage differences in friction between the two directions varied from 3.0 per cent. to 130 per cent. At 70 per cent. relative humidity and 70°F. the mean was 66.0 per cent., the standard deviation 17.6 per cent. and the coefficient of variability 26.6 per cent. No difference in scaliness between different fineness groups within a staple was obtained. Between samples, however, a significant negative correlation of -0.3428 between percentage difference in friction and fibre fineness was obtained. The value obtained for a sample was concluded to be characteristic of the sample, and not of any particular group of fibres used for the determination. The regression coefficient of percentage difference in friction on fibre fineness was -2.30, a significant value, showing that on the average the percentage difference in friction decreases by 2.30 per cent. for every micron increase in the fibre fineness of the sample. The values for coefficient of friction for the different quality numbers of South African Merino wool are given. Wool from rams gave a lower value for scaliness concordant with a coarser wool. The scaliness of the wool grown by three sheep on constant feed decreased with age, though no corresponding changes in fibre fineness occurred.Item Growth of the Albino rat with special reference to the influence of environment(Pretoria : The Government Printer, 1941) Murray, G.N.; Du Toit, P.J.Observations were made on Albino rats over a period of four years (1933-37); 238 litters were obtained comprising 2043 young at birth; 1789 (872 males and 917 females) were reared and weighed weekly. PRENATAL GROWTH. (a) Oestrus and service. The length of the oestrous period was 4 days in 60 per cent of the cases observed, 3 days in 20 per cent, and 5 days in the remaining 20 per cent cases. The time that vaginal plugs were visible varied from 6 hours to 10 days after service, the average being 1 to 2 days. Nearly all females were served during the night or early morning. Quite a large number of the females that had bred, had infected uteri. Here the ovaries were inactive except when only one horn of the uterus was affected; then the ovaries were active but the females did not become pregnant when served. (b) Weights of pregnant females. Different classes of females were used in studying the changes in weight of pregnant females: (1) Those served when the vaginas opened, (2) old virgins 8 to 11 months old and weighing about 200 g. and (3) females that had already had one or more litters. Only those pregnant for the first time showed an appreciable gain during the first two weeks of pregnancy, while rats that had had litters showed practically no gains. The weights of all females, however, increased rapidly during the last 7 to 8 days of pregnancy which is mainly due to the increase in weight of the developing foetuses. Only those rats pregnant for the first time showed an appreciable gain (56 per cent.) after parturition as compared with weight at service. This increase in permanent gain was equal to the gain during the first two weeks of pregnancy. Litter size at birth had no influence on the gains of the females during the first two weeks, hut during the third week the gains of the females increased with increase in litter size. (c) Weight and number of foetuses. Females of the three classes mentioned above were killed at different stages of pregnancy. The pregnant uteri showed an increase in weight only from the 6th or 7th day onward after service. By means of the method we used, foetuses could be weighed only from the 13th day onward, whereas the number of foetuses could be determined macroscopically from the 7th to the 8th day of pregnancy. The three different classes of rats showed large differences in the number of prenatal deaths. In the case of the young females which were about 3 months old and pregnant for the time, there were only two dead foetuses out of 190, average number of living foetuses per litter 9.4. In the case of the old rats 8 to 11 months, pregnant for the first time and of those of more or less the same age but which had already had one or more litters, 38.5 per cent of dead foetuses were found during the last two weeks, in the former class the average being 4 living foetuses per female, in the latter 5. LITTER SIZES AND WEIGHTS AT BIRTH. During the first 24 hours the birth weights remained more or less constant, or could show a slight decrease for young born during the day. Mortality at birth was 1.4 per cent. This figure may be slightly higher since females often eat the stillborn. Average birth weights of males and females born alive were 5.19 g. and 4.96 g. respectively, and of stillborn 4.88 g. and 4.8 g. respectively. Average litter size was 7.4 but for litters in which there were stillbirths average size was 8.8. Sex ratio for all rats born was 94.5 per cent. It decreased from 163 to 77 as litter size increased from 3 to 9, then increased again to 129 as litter size increased to 12. Birth weights decreased with increase in litter size. After a litter size of 9 was reached, birth weights showed a tendency to remain constant. Birth weights increased with age of mothers while litter size decreased. When litter size remained constant then age of mothers did not show any regular effect on birth weights. Females 2 to 3 months old had average litter sizes of 8.4 and those 12 to 13 months old 4.7. This continuous decrease in average litter size from the youngest age class to the oldest, instead of the expected increase to a maximum followed by a decrease, may have been due to the greater prenatal mortality in the older females. Total litter weight decreased from 43.3 g. to 25.0 g. Age of mothers was more important in determining litter size than parity. The weight of the mothers immediately after parturition did not appear to influence the birth weights of the young when litter size remained constant. LITTER SIZES AND WEIGHTS AT WEANING. The average weaning percentage of all litters was 84.0. There was no pronounced drop with increase in litter size as was found in the pig for instance. The average birth weights of young weaned was 5.11 g., but for young that died shortly after birth only 4.87 g. Greatest postnatal mortality occurred during the first week after birth. Litter size at birth showed the same influence on weights at 2, 3 and 4 weeks as at birth, i.e., first a decreasing decline in average weight as litter size increased up to 9, then weights remained more or less constant up to the largest litter size (12). Although litter size at birth and at weaning showed practically a straight hue, the influence of litter size at weaning on the average weight was quite different and peculiar. There was first an increase, then a decrease, another increase and finally a pronounced decrease. The most likely explanation of this appears to be the effect on milk supply of rats of different ages and weights, which were not kept constant in this case. Rats in litters of which all were reared were heavier than rats in litters of which some were destroyed by the females. The young of females 8 to 9 months old were the heaviest at weaning, indicating that the milk supply was the highest at this period. This coincided more or less with the production of the third litter. As mentioned the weight of the mothers did not influence the average birth weights of the young. The weights of the mothers at parturition, however, had a decided influence on the average weight of the young at weaning. As the weight of the mother increased up to 260 g. the average weight of the young decreased, and after that increased again. This is probably due to difference in milk supply. It appeared that only in the case of young females did increase in weight of the mother accompany a decrease in the average weaning weight of the young, whereas in the case of the old females there was a tendency for the young to increase in weight with an increase of the weight of the mother. Young heavy females therefore appear to be poor milkers, probably due to excessive fat, while weight in old females is more likely due to greater muscle and bone development. Although the best females, i.e., those rearing the largest and heaviest litters, were retained, it does not appear that the fertility of the population had been raised during the four years. Selection was probably mainly for good mothers, poor mothers being discarded. This strain of albino rat has been in bred for so many generations that the stock is probably nearly homozygous for the number of eggs shed, showing that variation in litter size is probably only due to factors such as foetal atrophy. SEASONAL INFLUENCE. (1) Length of time females took to become pregnant. (2) Litter sizes and weights at birth and weaning. (3) Sexual maturity of females. (4) Weights and tail lengths. (5) Health. (1) From March to July, autumn and winter, the females remained long with males before they became pregnant, but from August to February it took a shorter time. After February there was a sudden increase which may have been caused by the decrease in length of days. Females appear to have been affected more than males. (2) The average birth weights decreased from 5.19 g. during the first year to 4.96 g. during the fourth year. Our average birth weights were appreciably lower than those obtained at the Wistar Institute. The average litter size was higher during the summer months, November to January (7.8), than during the winter months, May to July (6.8). Birth weights, when effect of litter size was eliminated, did not appear to have been affected. Weaning percentages showed a decided seasonal trend, being highest between May and June, then decreasing until August and remaining low until October, after which there was an increase. During the four years the weights at 2, 3 and 4 weeks have decreased. This may have been caused by the effect on milk production of the mothers as well as by the environmental influence directly. There were decided seasonal fluctuations which appeared to be about the same at 2, 3 and 4 weeks. The highest weights were obtained during the winter, with a decline during the spring and the lowest level coinciding with the warm months, October and November. The weights of the suckling females showed about the same seasonal trends as the weights of the young, so that milk supply may also have been affected. (3) The sexual maturity of the females was affected as follows. During the first year the vaginas opened when the females were 47.2 days old and weighing 100 g . and during the fourth year when they were 42.7 days old and weighing 95 g. (4) When the average weights of our rats are compared with those of the original stock at the Wistar Institute, our males are appreciably heavier at the different ages up to 20 weeks, while the females show practically no difference. There was a marked seasonal effect on the weights. The highest and lowest points shifted about 3 to 4 months as the rats become older - 4 to 16 weeks - indicating the influence of the month of birth, also that an early influence may persist until maturity. The highest weights for all ages were obtained for those born during May to August, then there was a decrease with the lowest weights from about October to February. It appears that after 8 weeks the ultimate weight of the rat is not affected any more, or only to a small extent, by the environment under which it grew up. Tail length was affected less than weight by the environment. Although temperature may have influenced the weights of the rats, it appears more likely that there may have been an effect by a combination of factors, probably temperature and humidity, while a change in the length of the days probably also affected the growth of the animals through the effect on the pituitary. (5) Lung trouble occurred in 12.2 per cent. of the males and 6.8 per cent. of the females. This trouble occurred mostly when rats were l6 to 20 weeks old - later cases were not recorded. The disease was most prevalent during the winter months, 35.1 per cent. of the cases, spring following with 30.5 per cent. and summer and autumn much lower (18.3 and 16.0 per cent. respectively). GROWTH AND FOOD INTAKE. Daily gains of suckling young showed an increase from birth to 13 days, milk supply being then adequate, a standstill or decrease in daily gains from 14 to 18 days, milk supply being the limiting factor, and a continuous increase in daily gains from 19 to 28 days after the young have become accustomed to solid food. As litter size increased from 4 to 7, females required 40 g. additional food for each additional young for the 28 days period and 98 g. for each additional young from 7 to 11. Food utilisation of females was lower than that of males and showed a much greater variability. When the same amount of food was given individually to pairs of males and females of the same weight, then there was no difference in the food utilization. The difference was, therefore due to the more rapid growth of the males when both sexes were fed ad lib.Item A note on the influence of a bloodmeal ration on porphyrin excretion in normal bovines(Pretoria : The Government Printer, 1941) Roets, G.C.S.; Du Toit, P.J.Results are presented showing the effect of dietary bloodmeal on the porphyrin excretion of four mature normal steers. Bloodmeal causes a higher excretion in the faeces of copro- and chloroform soluble porphyrins. The coproporphyrin excretion of the urine is increased but no chloroform soluble porphyrins could, however, be detected in animals fed on bloodmeal.Item A preliminary note on the temperature of the scrotal skin of the bull and its relation to air, skin, and body temperature(Pretoria : The Government Printer, 1941) Quinlan, J.; Riemerschmid, G.; Du Toit, P.J.(1) The scrotal, skin, and body temperatures of a Sussex bull have been measured in the open during the period 7.1.41 to 27.3.41, at a range of air temperature of 26.4°F., i.e., from 64.8°F. to 91.2°F. (2) There was a significant difference between the temperatures of the three areas of the scrotum. (3) There was no significant difference between scrotal temperature measurements taken on that side of the body exposed to direct sun's rays and those taken of the opposite side. (4) There was a significant relation between scrotal temperature and air temperature. (5) The mean skin temperature readings, taken on an area on the flank from which the hair had been removed, were 98.6°F. in the sun and 96.7°F. in the shade. (6) There was a relation between the skin temperature and the air temperature; an increase of 1°F. of air temperature resulted in an increase of skin temperature of 0.28°F. in the sun and 0.31°F. in the shade. (7) There was a significant difference between the skin temperatures taken in the sun and in the shade. (8) The range of body temperature was too small, i.e., 101°F. to 103.5°F., to find a definite correlation between body and air temperature. The observations must be repeated at higher and lower atmospheric temperatures to establish such correlation. (9) There was a direct correlation between body and scrotal temperatures. (10) The correlation between body and skin temperature showed that for 1°F. increase in body temperature the skin temperature increased 2.01°F. in the sun and 2.6° F. in the shade.Item Observations on artificial insemination of sheep with fresh and stored semen(Pretoria : The Government Printer, 1941) Quinlan, J.; Steyn, H.P.; De Vos, D.; Du Toit, P.J.(1) One hundred and ninety-six merino sheep, maintained under dry lot conditions, were submitted to artificial insemination with fresh and stored semen obtained from highly fertile merino rams. The resulting pregnancies were compared with eighteen control sheep which were mated normally. Table 16 shows the results in summarised form. (2) The technique employed in the operation was satisfactory, as indicated by the results in groups 2, 3 and 4. (3) The cause of failure to impregnate by stored semen is due to deterioration in fertilising capacity. The activity of the spermatozoa is not always an indication of their capacity to impregnate, although active motility is necessary for fertilisation. (4)The number of inseminations required to establish pregnancy, the gestation periods and the weights of the lambs born do not differ significantly from normal mating. (5) There were five cases of dystocia in the groups treated by artificial insemination as compared with two in the normal service group. One deformed lamb was born in the inseminated groups. No importance is attributed to these occurrences. (6) The lambs born were of normal weight and their post-natal development was excellent. (7) A field observation was carried out on 680 Karakul sheep; 378 lambs were born with a mean gestation period of 150.1 days. These sheep were divided into two groups because of their condition: 482 sheep were suckling lambs; of these 319 became pregnant and 324 lambs were born. The percentage pregnancy was 66.1848. The other group was not suckling lambs and was fat. There were 198 ewes inseminated of which only 51 became pregnant and gave birth to 54 lambs. The percentage pregnancy was only 25.7599. There is an indication that the fat condition of the ewes rendered conception more difficult. (8) The artificial insemination of sheep with fresh semen or with semen stored up to 12 hours will give satisfactory results in sheep husbandry in South Africa. However, it is suggested that the employment of artificial insemination has a limited value in reproduction of sheep when the local conditions are compared with those in countries where insemination has become a routine measure in the production of livestock. (9) No pregnancies followed insemination with semen stored longer than 72 hours. (10) Artificial insemination overcomes the difficulty experienced in mating sheep with extreme tail development. It has proved satisfactory with the Karakul and Ronderib-Afrikaner. (11) Dilutor with pH value of 6.9 to 6.99 gave the most satisfactory results.Item Sex-physiology of sheep. Studies on the nature of the onset of oestrus in ewes following a period of sexual inactivity(Pretoria : The Government Printer, 1941) Quinlan, J.; Steyn, H.P.; De Vos, D.; Du Toit, P.J.1. Ninety-nine maiden Merino ewes, between the ages of 27 and 33 months, kept in an enforced environment in "dry lot" were submitted to a 3 hourly test for oestrus, from 6 p.m. to 6 a.m., at the commencement of the usual breeding season, following a period of anoestrus. 2. Forty-seven ewes showed oestrus. The oestrus was preceded by a definite period of "onset" in fifty-four out of sixty-five cases: There was a definite period of disappearance on fifty-six out of sixty-five cases. 3. The actual average duration of a total of sixty-five normal oestrous periods was 8.215 hours, with an estimated average of 14.585 hours. This is considerably shorter than that previously recorded in this country when observations were not confined to the onset of the breeding season, but were carried out throughout the year. 4. The duration of the dioestrous period averaged from nineteen normal cycles was 15.882 days. 5. "Weak oestrus" was a common occurrence. It was observed ninety-six times. It occurred in sheep which previously or subsequently showed normal oestrus: 29.27 per cent. of the ewes showed "weak oestrus'' only. It was or was not followed by ovulation. The average duration of ninety-six weak oestrous periods was 20.094 hours. In 68 occurrences in sheep which showed "weak oestrus" only, the average duration was 19.015 hours. In twenty-eight occurrences in sheep which showed normal oestrus in addition to "weak oestrus" the average duration of "weak oestrus" was 22.714 hours. 6. The duration of the interval between one "weak oestrus" and another (33) was 11.015 days. The interval between normal and “weak oestrus” (12) was 11.208 days. The interval between “weak” and normal oestrus (19) was 12.803 days. The duration of the interval between the total weak oestrus periods (45) was 11.067 days. The dioestrous period, when a "weak oestrus" was concerned, either at the commencement or the termination, was shorter by four days than that between normal oestrous periods. 7. Ovulation may or may not follow periods of "weak oestrus". 8. The hormones governing genital activity appear to reach a low-level output during the months of October and November. This seasonal genital quiescence appears to be the result of environmental factors other than nutrition, because sheep fed in "dry lot" on a regulated ration behave in the same way as veld-fed sheep. 9. The return to sexual activity at the commencement of a breeding season is, in many cases, a gradual process, the high-level secretion of the gonadotrophic hormone and the follicular hormone, necessary to produce full oestrus and ovulation, may not be reached at once, so that "weak oestrus" with or without ovulation is a frequent occurrence. 10. Individual sheep react differently, some with delayed response, to the extroceptive stimuli which initiate sexual activity at the commencement of the breeding season. During the period 20th November 1939 to the 20th December 1939, out of 99 sheep, kept in "dry lot" in a controlled environment on a similar level of nutrition, 47.47 per cent. showed normal oestrus of a shorter duration than that usually observed; 25.27 per cent. showed "weak oestrus" only; 27.26 per cent. did not show sexual activity.Item Bionomic studies on cattle in the semi-arid regions of the Union of South Africa. IV. The ovarian cycle of heifers during summer(Pretoria : The Government Printer, 1941) Quinlan, J.; Bisschop, J.H.R.; Adelaar, T.F.; Du Toit, P.J.(a) To obtain information concerning the sexual activity of cattle under the environmental conditions prevailing in the north western, semi-arid, summer rainfall areas of the Union of South Africa, a series of sex-physiological researches are being carried out at the Veterinary Research Station, Armoedsvlakte, near the town of Vryburg, in the Cape Province. (b) This article reports upon the sexual activity of groups of 2 year old, 7/8th bred, Afrikaner, Fries, Redpoll and Sussex heifers, which were tested for oestrus day and night at one hourly intervals from January 3rd to February 15th, 1940, i.e., during full summer conditions. (c) The experimental animals, the prevailing environmental conditions and the technique employed to record sexual activity, are described. (d) The results of the investigation show that the bonemeal fed heifers were sexually much more active than the heifers which received no phosphutic supplement. Nutritional deficiency therefore affected sexual activity. (e) The duration of the ovarian cycle, not only of the groups, but also of the individual experimental heifers, fell within the standard range of 17 to 24 days, as found in textbooks. The Armoedsvlakte environment did not influence the duration of the ovarian cycle. (f) The standard range for the duration of oestrus proper is given in textbooks as 18 to 24 hours. During the investigation, the average duration for the Afrikaner group was 7.88 hours; for the Fries 11.67 hours; for the Redpolls 14.00 hours, and for the Sussex 9.00 hours; for the exogenous breed groups together it was 11.74 hours. Of the 86 oestrous periods recorded no less than 81, or 94 per cent. were shorter than 18 hours. At Armoedsvlakte the environment shortened the duration of oestrus to a very significant degree, i.e. compared with the accepted standard range. (g) The results indicate, but do not prove, a difference in duration of oestrus proper between indigenous and exogenous types of heifers. With more information it is probable that such a type difference will be demonstrated. (h) The available data show that the oestrus proper of the Afrikaners was shorter than that of the Fries and Redpolls, and that the Redpolls have a longer duration than the Sussex. With more data, other significant breed differences will probably emerge. (j) Observations on the reactions of heifers to actual services by "teaser" bulls and on the use of aproned bulls (which cannot serve the heifers) suggests that oestrus proper is shortened in duration by the former method. (k) Oestrus proper was preceded by a period during which sexual activity waxed and was succeeded by a phase during which activity waned. The period of "onset" of oestrus varied from 5.19 to 8.78 hours in the individual breed groups, and the average period of "disappearance" from 5.00 to 7.45 hours. No breed group differences were found. In both phases, the frequency distribution showed a dominant tendency to short durations.Item The carotene content of some South African feeds(Pretoria : The Government Printer, 1941) Myburgh, S.J.; Du Toit, P.J.1. Carotene values were determined by analysing veldgrass samples, collected monthly in the areas, Onderstepoort (Pretoria district), Ermelo (Transvaal Highlands) and Vryburg (Bechuanaland). 2. From the values for Carotene found, the daily intake was calculated and one can safely conclude that no deficiency of Carotene existed for the season August, 1939, to August, 1940, for all the areas in question. During 1938, due to low rainfall in the Vryburg area, a low intake of Carotene was registered, which was, however, still above the minimum requirement of 9 mgms. daily. Low intakes for a few months in winter (during dry periods) were found, but these instances were the exception rather than the rule.Item The nutritive value of animal proteins : the biological values of fishmeal, whale and fishmeal, meatmeal, meat and bonemeal, crayfishmeal, and white fishmeal(Pretoria : The Government Printer, 1941) Du Toit, B.A.; Smuts, D.B.; Du Toit, P.J.By means of nitrogen metabolism experiments, the biological values of 94 for white fishmeal, 81 for crayfishmeal, 71 for fishmeal, 67 for meatmeal, 67 for meat and bonemeal and 63 for whale and fishmeal were determined. From these figures and the digestibility coefficients it was shown that white fishmeal is superior in its utilizable protein content, and that whale and fishmeal is the poorest in this respect.Item A study on the possibility of cystine synthesis in the rumen of sheep together with the effect of cystine supplementation on the nitrogen utilization of lucerne in young stock(Pretoria : The Government Printer, 1941) Smuts, D.B.; Du Toit, B.A.; Van der Wath, J.G.; Du Toit, P.J.By means of metabolism experiments on rats it was shown that the biological value of the rumen ingesta is better than that of lucerne. When rumen ingesta are supplemented by cystine their biological value is significantly enhanced. In sheep experiments it was shown that the inclusion of cystine in a lucerne ration for mature sheep did not influence the biological value of the latter. For growing sheep the supplementation of lucerne by cystine increased its biological value by 10 per cent. It is concluded that the action of the micro-organisms is purely a question of interception, that is, utilizing exogenous protein for its own use and supplying it back to the animal in the bacterial and infusorial form.Item The endogenous nitrogen metabolism of pigs with special reference to the maintenance protein requirement(Pretoria : The Government Printer, 1941) Du Toit, B.A.; Smuts, D.B.; Du Toit, P.J.The endogenous nitrogen metabolism of pigs have been measured and an equation evolved for the estimation of the maintenance protein requirements of pigs. The equation obtained is P=0.79 W·⁷³⁴, where P=protein in grams, and W weight in Kgm.Item South African Senecio alkaloids. Part 5. Notes on Isatidine, Rosmarinine and Pterophine, and on the structure of their necines and necic acids(Pretoria : The Government Printer, 1941) De Waal, H.L.; Du Toit, P.J.1. Isatinecine has a pyrrole nucleus and has no tertiary nitrogen atom. It must, therefore have a secondary aminogroup. The pyrrollizidine structure applicable to the two senecio bases retronecine and platynecine is, therefore, not present in isatinecine and, therefore, also not in isatidine (no tert. N-atom). 2. Isatinecine has two double bonds, the introduction of which into the pyrrollizidine molecule is not compatible with the empiric formula for isatinecine. In agreement with these properties a basic structure for isatinecine is proposed, in which the pyrrollizidine bicyclic system has opened at the point of intersection where the N-atom is situated. 3. Isatidine has one peroxygen atom which is present in the esterifying acid, isatinecic acid, which is a free peracid with one percarboxylgroup (R. CO. O. OH) which readily lactonizes. 4. The isolation of a new alkaloid pterophine is described. It has the formula C₁₈H₂₃O₅N, m.p. 227 -8°C. and [∝] 18/D = -88.5 (1.875% in CHCl₃). The alkaloid is present in both S. pterophorus and S. ilicifolius and is toxic. 5. Pterophine has a pyrrole nucleus and a tertiary N-atom which readily forms a methiodide. The nitrate and the picrate of the alkaloid have also been prepared. 6. Upon the hydrolysis of pterophine with alcoholic potash it yields the well-known senecio base retronecine and a new acid lactone (probably C₁₀H₁₆O₆). * 7. The hydrolysis with bariumhydrate of the new senecio alkaloid rosmarinine is described. The fission products are a new base rosmarinecine (C₈H₁₃O₃N) and senecic acid, C₁₀H₁₄O₄. Rosmarinine has a tertiary N-atom, which forms a methiodide and has the pyrrole nucleus. 8. Platynecic acid (the necic acid of platyphylline) is identical with senecic acid (the necic acid of senecionine and rosmarinine). 9. Besides retrorsine, S. graminifolius contains a new alkaloid, graminifoline (probably C₁₈H₂₃O₅N) in very small amounts. 10. Retrorsine is also present in S. pterophorus and S. ilicifolius.Item Recent investigations into the toxicity of known and unknown poisonous plants in the Union of South Africa. XI(Pretoria : The Government Printer, 1941) Steyn, D.G.; Van der Walt, S.J.; Du Toit, P.J.The toxicity of sixteen plants was investigated. According to the available literature the following three plants were proved for the first time to be toxic: Senecio pterophorus DC; Kalanchoe paniculata Harv., Kalanchoe thyrsiflorae Harv. The results obtained in the experiments with Crotalaria rhodesiae Baker f. and Pseudogaltonia clavata (Baker) Phillips are not considered sufficiently conclusive to prove these two plants to be poisonous. The latex of Arauya serisifera Brot. was proved to possess irritant properties when applied to the skin. The Senecio alkaloids, isatidine and retrorsine, administered per os to horses induced symptoms, post-mortem appearances, and histological lesions typical of those of "dunsiekte" in horses, and these alkaloids are undoubtedly the active principles of the species of Senecio from which they were isolated.Item Description of a tick Rhipicephalus glabroscutatum, sp. nov., (Ixodidae) from the Karroo areas of the Union of South Africa(Pretoria : The Government Printer, 1941) Du Toit, R.; Du Toit, P.J.A new species of tick from domestic stock is described and figured belonging to the genus Rhipicephalus. It closely resembles R. oculatus, Neumann, a common species on hares in South Africa from which it may be distinguished by the shiny smooth scutum practically devoid of punctations. The life history is given as worked out by feeding on guinea-pigs and rabbits and the species is found included. The name Rhipicephalus glabroscutum sp. nov., is proposed.Item Further studies on the antigenic structure of paratyphoid bacilli with special reference to three new species of Salmonella(Pretoria : The Government Printer, 1941) Henning, M.W.; Rhodes, W.F.; Gordon-Johnstone, J.; Du Toit, P.J.Three new species of Salmonella are described. 1. S. durban was obtained from an adult native woman suffering from dysentery. The antigenic formula allocated to it was IX-a, enx. 2. S. reading var. kaapstad was isolated from the cerebrospinal fluid of a child suffering from meningitis. Its antigenic structure was found to be IV-eh: 1, 7. 3. Two unrelated organisms were isolated from one of a group of pigs affected with paratyphoid. The one turned out to be S. heidelberg, factors IV, V-r: 1.2, while the other was found to be a new species with the following antigenic structure: XI- k: 1,2. The latter was named S. pretoria. 4. The biochemical reaction of these organisms are given in Table 1.Item The diagnosis of chronic streptococcus mastitis : reaction, chlorine, methylene blue and Hotis tests, and microscopic examination(Pretoria : The Government Printer, 1941) Van Rensburg, S.W.J.; Du Toit, P.J.(1) An account is given of the abnormal conditions which may be encountered in the bovine udder and its secretion in chronic streptococcus mastitis. It is pointed out that, on account of these different manifestations of the disease, it is not possible for any single test to reveal the condition in all its forms. (2) The results obtained by the application of the alkalinity, chlorine, methyleneblue and Hotis tests and by microscopic examination are detailed. (3) For the estimation of the alkalinity of milk the British Drug Houses' Universal Indicator was compared with brom-thymol-blue in 123 samples and revealed 39.1 per cent. of infected samples as against 25 per cent. shown by brom-thymol-blue. (4) Chlorine determination was compared with alkalinity in 837 samples and detected a larger number of abnormal quarters, but its value as a test for mastitis is nullified by a tendency to show a large percentage of false positives on account of its sensitiveness to physiological as well as pathological factors. (5) The methylene blue reduction test was applied to composite samples from 32 infected and 15 clean cows. The reduction time was under 8 hours in 24 (75 per cent.) infected udders and in 1 (6.7 per cent.) streptococcus free udder. (6) Although reduction time is greatly reduced by mastitis streptococci, the reduction test cannot be regarded as specific for mastitis since reduction is also brought about by organisms other than mastitis streptococci. (7) There appears to be no correlation in streptococcus free milk between the reduction time and the chlorine content, alkalinity and sediment. (8) The Hotis test was applied to 269 individual quarter samples from 69 animals. It gives a high percentage of false positives and reliance can only be placed on its results if these are substantiated by microscopic examination of smears prepared from the milk after incubation. (9) A review of the literature dealing with microscopic examination of milk for the detection of mastitis streptococci is given. (10) The technique for preparing smears for microscopic examination is described. (11) It is concluded that microscopic examination of smears from fresh milk is unreliable while that of smears taken after centrifuging fresh milk is of limited value. On the other hand, smears prepared from 267 samples after incubation overnight detected 93.6 per cent. positives as against 88.8 per cent. revealed by cultural methods. (12) The lack of agreement between cultural and microscopic examinations in a small percentage of cases is attributed to the absence of infection in the particular sample in which the test concerned apparently failed. (13) In an examination of over 1,000 milk smears from quarters known to be free from mastitis streptococci long chain streptococci were detected in only one case. These, however, were not the same morphologically as mastitis streptococci. (14) The cell content of the milk as revealed in the smears provides a usefu1 indication of the extent of the changes in the quarter and in the milk. (15) For the detection of mastitis streptococci microscopic examination of smears made from milk that has been incubated overnight at 37°C. is just as reliable as cultural methods. It requires less time, labour and equipment and can easily be adapted to testing under field conditions.Item The electrophoresis of the neurotropic virus of horsesickness and its neutralizing antibodies in low concentration(Pretoria : The Government Printer, 1941) Polson, A.; Du Toit, P.J.1. By means of a modified form of the moving boundary method of electrophoresis of Tiselius, it was found possible to measure the rate of migration as well as the isoelectric points of viruses and their neutralizing antibodies in low concentrations. 2. The measurements were carried out on three antigenically different strains of horsesickness virus. It was found, within experimental error, that all three strains have the same isoelectric point as well as the same change of mobility with pH. 3. The similarity between the isoelectric points and the mobilities of serum albumin and horsesickness virus suggests a close relationship between the albumin and virus. The serum albumin can either be adsorbed on to the virus or the virus can have the same chemical composition as the albumin. 4. The mobilities and isoelectric points were determined of the neutralizing antibodies of strains 449 and OD. The same isoelectric point and the same change of mobility with pH were found for these two substances. 5. Attempts were made by means of electrophoresis on the separation of active virus from neutral virus antibody mixtures but with no success.Item The particle size of African horsesickness virus as determined by ultrafiltration and ultracentrifugation(Pretoria : The Government Printer, 1941) Polson, A.; Du Toit, P.J.(1) Details of the technique employed for the preparation of gradocol membranes are given together with the technique employed in the filtration of neurotropic horsesickness virus. (2) From data collected from the filtration of 6 strains of virus it is found that the limiting membrane is one with a porosity of 100 mµ. Hence the diameter of the virus particles is from 40-60 mµ with a mean of 50 mµ. (3) Details of the technique used for determinations by the inverted capillary method of centrifugation are given. (4) The method used for determining the density of the virus particles is given. By this method a density of 1.25 gm. per c.c. was calculated. (5) By the centrifugation method a mean value of 45.4 mµ for the particle diameter was calculated. (6) The particle diameter determined by both methods agree closely. (7) There was no significant difference in the size of the virus particles of 6 strains of different antigenic structure.