6 



HUMAN BODY. 



epidermis does not. Between the skin and the lining serous 

 membranes are bones, muscles (the lean of meat), and a great 

 number of other structures which we shall have to consider 

 hereafter. All cavities inside the body, as the alimentary 

 canal and the air-passages, which open directly or indirectly 

 on the surface are lined by soft and moist prolongations of 

 the skin known as mucous membranes. In these two layers 

 are found as in the skin, but the superficial bloodless one is 

 called epithelium and the deeper vascular one corium. 



Diagrammatically we may represent the Human Body 

 in longitudinal section as in Fig. 2, where aa' is the dorsal 

 or neural cavity, and b and c, respectively, the thoracic and 

 abdominal subdivisions of the ventral cavity; d represents 

 the diaphragm separating them ; ee is the vertebral column 

 with its modified prolongation into the head beneath the 

 anterior, enlargement of the dorsal cavity; / is the ali- 

 mentary canal opening in front through the nose, ?', and 

 mouth, 0; li is the heart, I a lung, s the sympathetic nervous 

 system, and k a kidney. 



A transverse section through the chest is represented by the 

 diagram Fig. 3, where x is the neural canal containing the 

 spinal cord. In the thoracic cavity are seen the heart, h, 



FIG. 3. A diagrammatic section across the Body in the chest region, x, the 

 dorsal tube, which contains the spinal cord; the black mass surrounding it is a 

 vertebra; a, the gullet, a part of the alimentary canal; h, the heart; sy, sympa- 

 thetic nervous system; M, luags; the dotted lines around them are the pleurae; IT, 

 ribs; st, the breast-bone. 



the lungs, II, part of the alimentary canal, a, and the sympa- 

 thetic nerve-centres, sy ; the dotted line on. each side covering 

 the inside of the chest- wall and the outside of the lung 

 represents the pleura. 



Sections through corresponding parts of any other Mam- 

 mal would agree in all essential points with those represented 

 in Figs. 2 and 3. 



