SELECTION OF A BREED 21 



of the hog, therefore, is not in the true sense of the word, 

 a part of the animal. It is outside of its circulatory and 

 nervous systems and it therefore does not matter much 

 whether this part of the animal becomes heated or not. 

 The cuticle, as well as the true skin, of the hog is of such 

 a nature that it is not a reflector like a mirror; it is not 

 a polished surface, but will allow the rays of the sun 

 either to pass through it or to be absorbed. The white 

 cuticle, since it is not a reflector, will allow the rays to 

 pass through ; the black cuticle, being dark, will act as an 

 absorbent. The cuticle of the black hog, then, which ab- 

 sorbs the heat of the sun, apparently plays the double 

 part of conductor and radiator. This part being hotter 

 than the adjacent portions of the carcass, part of the heat 

 will be conducted into the body of the hog, another part 

 will be conducted to adjacent particles of air, and still 

 more will be radiated into space. Thus the black hog 

 gets only a part of the heat from the sun in the interior 

 of his body, while the white hog, whose cuticle is 

 neither a reflector nor an absorbent, gets the bulk of the 

 heat from the sun in the living part of its carcass. This 

 apparently is detrimental and is responsible for the fact 

 that white hogs are not as adaptable to hot climates hav- 

 ing a great deal of sunlight as black hogs. 



In general, then, white hogs may be selected for north- 

 ern climates, but the dark breeds, either red or black, 

 should be selected for southern climates. Of course if 

 southern climates have very little sunshine, or if the hogs 

 are well provided with shade, the white hog will still do 

 very well in the south. Furthermore, if the northern 

 climates have an abundance of sunlight, the white hog 

 would also be handicapped in such places. 



