72 



DOMESTIC PIGS. 



Chap. III. 



of the head of a wild boar and of a sow from a photograph of 

 the Yorkshire Large Breed, may aid in showing how greatly 

 the head in a highly cultivated race has been modified and 

 shortened. 



Nathusius has well discussed the causes of the remarkable 



changes in the skull and 

 shape of the body which 

 the highly cultivated races 

 have undergone. These 

 modifications occur chiefly 

 in the pure and crossed 

 races of the S. Indicus type ; 

 but their commencement 

 may be clearly detected in 

 the slightly improved breeds 

 of the 8. scrofa type. 17 

 Nathusius states positively 

 (s. 99, 103), as the result of 

 common experience and of 

 his experiments, that rich 

 and abundant food, given 

 during youth, tends by some 

 direct action to make the 

 head broader and shorter; 

 and that poor food works a 

 contrary result. He lays 

 much stress on the fact that 

 all wild and semi^domesti- 

 cated pigs, in ploughing up 

 the ground with their muz- 

 zles, have, whilst young, to 

 exert the powerful muscles 

 fixed to the hinder part of 

 the head. In highly cultivated races this habit is no longer 

 followed, and consequently the back of the skull becomes 

 modified in shape, entailing other changes in other parts. There 

 can hardly be a doubt that so great a change in habits would 



Fig. 3.— Head of Wild Boar, and of " Golden Days," 

 a pig of the Yorkshire Large Breed; the latter 

 from a photograph. (Copied from Sidney's edit, 

 of ' The Pig,' by Youatc.) 



17 < 



Scliweineschadel,' s. 74, 135. 



