DISEASES AND. PARASITES OF MAM M^A L S 95 



though all the domesticated animals are introduced, not native to the 

 range in which the plants occur. It is possible that the native mammals, 

 having developed side by side with the poisonous plants, may be even 

 more careful to avoid them or in some instances may have established 

 more or less complete immunity from the poison, but there is not very 

 definite evidence bearing upon this subject. Some mammals appear to 

 be immune from poisons which affect others. Thus some squirrels eat 

 mushrooms which are quite poisonous to human beings. 44 



44 Odell, Canadian Field Naturalist, xxxix, 180-181, 1925 ; XL, 184, 1926. 



