GENERAL PLAN OF BODY. 



concerned in keeping up the 

 blood flow (organs of circula- 

 tion), in breathing (organs of 

 respiration) and in digesting 

 food (organs of digestion). It 

 does not reach up into the neck, 

 but is entirely confined to the 

 trunk. The smaller cavity, a, 

 a', is tubular in the trunk region, 

 but passes on through the neck, 

 and widens out in the skull ; it 

 is known as the dorsal or neural 

 cavity, and contains the most 

 important nervous organs, the 

 brain, N', and spinal cord, N. 

 In the partition between the two 

 cavities is a stout bony column, 

 the backbone or spine, e, e, 

 which is made up of a number of 

 short thick bones piled one on 

 the top of another. 



Man is a vertebrate animal. 

 The presence of these two 

 chambers with the solid par- 

 tition between them is a prim- 

 ary fact in the anatomy of 

 the body ; it shows that man is 

 a vertebrate animal, that is to 

 say, is a back-boned animal, 

 and belongs to the same great 



What lies between the haemal and 

 neural cavities? Of what is the spine 

 composed ? 



Fia. 1. Diagrammatic longitud- 

 inal section of the body. , the 

 neural tube, with its upper enlarge- 

 ment in the skull cavity at a'; N, 

 the spinal cord; N', the brain; ee, 

 vertebrae forming the solid parti* 

 tion between the dorsal and vent- 

 ral cavities; 5, the pleura!, and, e, 

 the abdominal division of the 

 ventral cavity, separated from one 

 another by the diaphragm, 'd; i, 

 the nasal, and o. the mouth cham- 

 ber, opening behind into the 

 pharynx, from which one tube 

 leads to the lungs, /, and another 

 to the stomach,/; A, the heart; k, 

 a kidney ; s, the sympathetic 

 nervous chain. From the stomach, 

 f. the intestinal tube leads through 

 the abdominal cavity to the pos- 

 terior opening of the alimentary 

 canal, 



