GENERAL VIEW, 



3 



work (the bony skeleton), on which are laid bundles and layers 

 of flesh or muscle, the whole being enclosed by skin. 



An external opening, the mouth, is the beginning of a long 

 and convoluted alimentary tube, which varies in size in dif- 

 ferent parts before reaching its termination, and has annexed 

 to it a variety of glands, as the liver, pancreas, and salivary 

 glands. This long tube occupies part of a great internal 

 cavity in the trunk of the body, in which cavity are also 

 placed the heart, lungs, spleen, kidneys, and bladder, the 

 heart 1 being situated on the ventral aspect of the cavity. 



FIG i. A DIAGRAMMATIC SECTION OF THE HUMAN Horn- TAKEN VERTI- 

 CALLY THROUGH THE MEDIAN PLANE. 



The ventral cylinder, containing the convoluted alimentary tube, lungs, &c. f 

 is bounded by the thick black line. 



The dorsal cylinder, bounded by oblique lines, is shown expanding above into 

 the brain cavity. 



5. Thus man's trunk may be conceived as a sort of fleshy 

 cylinder, but in fact it is made up of two cylinders of very 

 different size and structure. 



1 The various organs here enumerated by anticipation are described in sub- 

 sequent Lessons. 



B 2 



