ANIMALS WITH A BACKBONE. 



131 



Fig. 143.— Side-view of 

 the vertebral column 

 or backbone of man. 



Fis. 144.— Diagrammatic longitudinal sec- 

 tion of the human body, o, the neural 

 tube, with its upper enJargement in the 

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

 N', the brain; ee, vertebrae forming the 

 solid partition between the dorsal ajid 

 ventral cavities; 6, tlie pleural, and c, 

 the abdominal, divisions of the ventral 

 cavity, separated from one another 

 by the diaphragm, d; i, the nasal, and 

 o, the mouth chamber, opening behind 

 into the pharynx, from which one tube 

 leads to the lungs, I, and another to the 

 stomach, /; A, the heart; /c, 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 tjavities, — ^the nervous one 

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



