ANIMALS WITH A BACKBONE. 



137 



a\ 



FIG. 143. Side-view of 

 the vertebral coluinu 

 or backbone of man. 



N 



FIG 144. Diagrammatic longitudinal sec- 

 tion of the human body. , the neural 

 tube, with its upper enlargement in (lie 

 skull-cavity at a'; N, the spinal cord; 

 N', the brain; ee, vertebrae forming the 

 solid partition between the dorsal and 

 ventral cavities; b, the pleural. and t, 

 the abdominal, divisions of the ventral 

 cavity, separated from one another 

 by the diaphragm. (7; /, the nasal, and 

 o, the mouth chamber, opening behind 

 into the pharynx, from which one tube 

 leads to i he lungs. /. and another to the 

 stomach, /; /i, the heart; k, a kidney; 

 s, the sympathetic nervous chain. 

 From the stomach, /, the intestinal 

 tube leads through the abdominal cav- 

 ity to the posterior opening of the ali- 

 mentary canal. 



intestine. Thus there are two cavities, the nervous one 

 above, and the visceral one below, the backbone (Figs. 143, 



