156 THE SHAPES AND SIZES OF ANIMALS 



they are subject to a variety of ailments, which 

 more or less incapacitate them for their work, so 

 that the elephant seems in real danger of being 

 shouldered out of existence by the steam engine 

 and hydraulic jack, which are more reliable, easier 

 to apply, and on the whole less costly. Enormous 

 numbers of elephants, both African and Indian, are 

 killed each year for the sake of the ivory of which 

 their tusks consist ; it is difficult to form anything 

 like a correct estimate of the actual number, but 

 competent authorities state that it cannot be less 

 than 100,000 annually. This terrible destruction is 

 admittedly thinning their numbers, and elephants are 

 on all hands recognised as doomed to destruction ; 

 and with the whales, which are yearly becoming 

 scarcer, to form the last and greatest victims of a 

 ruthlessly advancing civilization. 



A final problem, that time only permits me to 

 hint at but which has been keenly discussed by 

 many writers, is this. Why is it, how does it 

 come about, that some animals are so much bigger 

 than others ? To take a concrete case : why is a 

 cow bigger than a sheep ? The two animals 

 belong to closely allied groups ; we see them side 

 by side in our fields, eating the same food and 

 digesting it in the same characteristic fashion ; 

 why then should there be so great and constant a 

 difference in size ? Herbert Spencer, who discusses 

 the problem at some length, is inclined to explain 

 it by the size of the animal at birth, and attempts 

 to establish the position that those animals which 

 are larger at the time of birth or of hatching are 



