DIFFERENCES IN SUSCEPTIBILITY TO POISONING. 35 



In the winter of 1898-99,4,700 sheep were poisoned from eating 

 lupine ha}^ and 1,812 died. In the season of 1900, 150 cattle were 

 poisoned apparent!}^ from eating false lupine and 100 died. 



EXPERIMENTS ON RABBITS. 



Most excellent facilities for observing cases of stock poisoning as 

 they occurred in the field were afforded us in 1900 from ]May until 

 July, but often it was impossible for either of us to be on hand when 

 the animals were first poisoned. In practically all accidental cases 

 occurring on the ranges it is impossible to make anj^thing like a sat- 

 isfactory inspection of the s3^mptoms of poisoning or to estimate the 

 quantity of the plant eaten, and it is often difficult even to deter- 

 mine the plant, still more the particular part of the plant which 

 caused the mischief. Besides, the accidental cases ordinarily observ- 

 able cover about five or six of the several dozen plants which have 

 been cast under suspicion by the stockmen of Montana and concern- 

 ing which it was necessary that they should have some definite infor- 

 mation. For these reasons it was necessary to make numerous experi- 

 ments with various plants on inexpensive animals. Rabbits were 

 selected for this purpose because, being herbivorous in their nature, 

 they more closely resemble stock, so far as their eating habits are 

 concerned, than any other commonly domesticated pets. The neces- 

 sity of choosing by this standard is apparent when one considers the 

 wide difference in the susceptibility to certain poisons shown in vari- 

 ous animals having different feeding habits and corresponding differ- 

 ences in the nature and extent of the digestive areas in the stomach 

 and intestinal canal. So, too, there is a difference in the susceptibility 

 which is somewhat correlative to the general, and especially to the 

 mental, development of the animal.' The brain and nerve poisons, 

 such as morphine, atropine, conine, and aconitine, are much less poi- 

 sonous to animals than to men. Dogs and horses can, in proportion 

 to their weight, endure ten times as much morphine as men, while 

 doves can stand five hundred times and frogs even a thousand times 

 as much. In herbivorous animals, especiallv in those which chew 

 their cud, such as sheep and cattle, the digestive tract is much longer 

 than in the case of omnivorous or carnivorous animals, consequently 

 the food remains in the body for a much longer period. In case of 

 herbivorous animals this period is usually several da^^s, while in car- 

 nivorous animals it is about twenty -four hours only. In the former 

 case, therefore, the poison would have much more time to become 

 absorbed into the blood than in the latter case. This, according to 

 Frohner, probably explains why it is that the metallic poisons are 

 much more fatal to herbivorous than to carnivorous animals. The 

 fatal dose of calomel is given for a cow as practically the same as that 



' See Frohner, Lehrbuch der Toxicologie fiir Thierarzte, pp. 12, 13. 1890. 



