in FOOD AND POISON 141 



varieties. The Pyrenean sheep feed without injurious 

 effects on the leaves of Quercus tosa, while imported 

 Southdovvns are killed by this plant. Lychnis Githago 

 is very unequally toxic for different species ; calves 

 require 2 g. 50 centigr. per kilogram of weight of 

 flour, while the hog requires only one gramme, and 

 the dog ninety centigrammes, to be killed. Similarly, 

 while the horse is killed by two kilograms of fresh 

 hemlock, the ox requires at least double this amount. 

 Cyclamen europceum is very dangerous for man, and 

 hardly at all for hogs ; it kills fishes and some other 

 aquatic animals, while many Crustacea and different 

 insect larvae do not suffer at all. 



Of course, there are many reasons for these dif- 

 ferences in the influence of poisons, and in some cases 

 we perceive them easily. But in others there is some 

 intimate unknown reason which would require investi- 

 gation, such as the case of the Pyrenean and South- 

 down sheep. Even if there is merely here a case of 

 habitual adaptation a mere verbal explanation 

 such as is very often met with in experiments on the 

 influence of toxic media on animals or plants, or on 

 the influence of pathogenetic organisms on higher 

 beings, there must be some difference between the 

 organisms which perfected methods will be able to 

 detect. There may be here some acquired character, 

 some peculiar variation which has become inherited. 



