It is possible to cause the development of tolerance in animals, to certain poisonous plants, by drenching them with small and increasing quantities, whilst others do not produce this phenomenon and may even cause sensitisation, or have cumulative effects.
The well known fact that animals, newly introduced to farms infested with poisonous plants, are much more liable to succumb to plant poisoning than animals born and reared on such farms, is most probably partly due to an acquired tolerance developed in the course of time by repeatedly partaking of small quantities of these plants. It is fully realised that discriminate feeding, which is a characteristic of stock reared in areas infested with poisonous plants, plays a very important role in the prevention of plant poisoning in these animals.
Theories of tolerance and desensitisation are discussed.
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