4 THE HUMAN BODY 



Upon the ventral side of the head is the mouth-opening leading 

 into a tube, the alimentary canal, /, which passes back through the 

 neck and trunk and opens again on the outside at the posterior 

 part of the latter. In its passage through the trunk-region this 

 canal lies in the ventral cavity. 



The Mammalia. In many vertebrate animals the ventral cavity 



FIG. 1. The Body opened from the front to show the contents of its ventral 

 cavity, lu, lungs; h, heart, partly covered by other things; le, le', right and left 

 liver-lobes respectively; ma, stomach; ne, the great omentum, a membrane con- 

 taining fat which hangs down from the posterior border of the stomach and covers 

 the intestines. 



is not subdivided, but in the Mammalia it is; a membranous trans- 

 verse partition, the diaphragm (Fig. 1, 2), separating it into an 



