14 



MAMMALS 



strange and abnormal development, being in the case of 

 the upper ones useless. Instances have been known 

 in which these strange tusks turned and grew into the 

 flesh. 



The anatomy of the mammals (Fig. 7) is interesting. 

 Food taken in at the mouth is chewed or ground up by 

 the teeth, mixed with saliva. Thence it passes down the 

 esophagus (g-) into the stomach (//). Here it is mixed 



Fig. 7. — Ideal Section of a Mammalian Vertebrate. 



A, pectoral, or lore limb ; B, pelvic, or hind limb ; a, mouth ; 3, cerebrum ; c, cere- 

 bellum ; d, nose ; e, eye ; /, ear ; ^, esophagus ; /i, stomach ; i, intestine ; j, dia- 

 phragm, or midriff; ^, rectum, or termination of intestine; /, anus; m, liver; 

 n, spleen; o, kidney; p, sympathetic system of nerves; ^, pancreas; r, urinary 

 bladder; s, spinal cord; «, ureter; v, vertebral column; w, heart; x, lung; 

 y, trachea, or windpipe ; s, epiglottis. 



with a secretion called gastric juice. Known as chyme, it 

 passes into the smaller intestine (/), where it is brought 

 into contact with various secretions, as pancreatic juice and 

 bile. It is now known as chyle, and finally passes to the 

 blood vessels. Food is Hterally fuel for the living machine, 

 and the simple act of eating is, roughly speaking, a mar- 

 velous transformation of crude matter into the bone and 

 sinew of animal life. 



