4 AGE OF THE DOMESTIC ANIMALS. 



which force them to remain quietly in their nests while their 

 mothers are away, and until they have acquired considerable 

 force and strength. In all species the young are born with a 

 short down over the body, which serves to protect them from cold 

 ftnd wet ; if the animals are pigmented, this is lighter in color 

 than the coat will be later. The brain and head are always 

 large, and overhang the little faces. The digestive tract is well 

 developed, and frequently gives the belly a swelled appearance. 

 The tissues are soft; the bones, scarcely formed, are flexible; 

 and while, on the one hand, they may favor deviations and de- 

 formity, on the other they allow of considerable displacement 

 in the helpless animal without injury to it; the liver is enor- 

 mous, from its activity in intra-uterine life; the lymphatic 

 ganglia are large, as are the thymus glands and supra-renal 

 capsules ; the ventricular portion of the heart and the arteries 

 exceed the veins in size ; the lungs are well developed, the 

 kidneys the same, and the nervous system is relatively ex- 

 cessive in size, while the organs of generation may be almost 

 rudimentary. 



The functions of the organs are in co-relation with their 

 development. That of digestion is most prominent, and, in- 

 deed, is the first and only one in the very young animal, for 

 which it uses its intelhgence to direct voluntarily, searching 

 and crying for food almost as soon as born, to find, at the 

 teats of the mother, the nutrition which was interrupted at 

 the rupture of the umbilical cord. Digestion and assimila- 

 tion of food take place rapidly ; the circulation of the blood is 

 frequent ; the secretion of saliva, pancreatic fluid, and bile is 

 active, while the excretion of waste matter is small. The rapid 

 chemical changes in the tissues of the very young is productive 

 of a high body temperature. 



The function of relation is somewhat limited in the young 

 herbivora, which, however, see, can guide themselves, and move ^ 

 considerable distances ; the sense of hearing and taste is de- 

 veloped, while that of smell is almost absent. In the young 



