HG aa PHYSIOLOGY OF THE HUMAN BODY. 
tongue, it is moved onward through the gullet by the continual contrac- 
tion of the elastic rings behind it. In this manner, the food finds its way , 
into the stomach. The course taken by the food will be best understood 
from an outline sketch of the Alimentary Canal (fig. 52), which is the 
whole digestive apparatus through which the food passes. The gullet (a), 
in its passage to the stomach, passes through an opening in the diaphragm, 
a large, flat muscle, which forms the partition between the chest and the 
abdomen. Immediately below this, it enters the stomach, a large, mus- 
cular bag (b), widest at the end where the gullet enters (c); from the 
narrower end proceeds the smaller intestine, which is generally about 
twenty feet long, and, rolled up in numerous folds (e, e), occupies the 
middle of the abdomen. The small intestine is attached to the large 
intestine (h, 27, 7, k), which is about five or six feet long, and passes 
upward on the right side of the folds of the small intestine (the right 
side of the figure is the left side of the man), across to the left, and then 
down to the anus or lower orifice of the alimentary canal, by which its 
contents are discharged. 
4, Chymification. waren the food enters the stomach, the process of 
digestion immediately begins. This consists in the reduction of the food 
to a thoroughly proken-tip, thin, pulpy mass, so as.to allow of the | 
nutritive part being received into the system. For this object, it is 
mixed with a fluid, Se the gastric? juice, which is secreted in a great 
many little bags in the walls of the stomach, and poured out whenever 
food enters the stomach. To facilitate this mixture, there is a provision 
made for stirring it about. The walls of the stomach are composed partly 
of strong muscles; and when the food enters, which it does at the upper 
left-hand corner (c, fig. 53), by the contraction of these muscles, it is 
pushed towards the right, along the top (a, a). When it comes to the right 
extremity, it is pushed bel to the left, but now nearly in the middle (6); 
a when it comes back to the left, 
the opening being firmly closed by 
muscles, it is divided into two streams 
—one going along the top, and the 
other along the bottom. By this means, 
the food is thoroughly mixed with the 
gastric juice, and reduced to a half- 
fluid pulp, called chyme [Greek chymos, 
juice]. The gastric juice consists of 
Fig. 53. two elements—an acid, and an organic 
matter called pepsine, from Greek pepto, 
to digest; and the uses of it are to dissolve and modify all animal 

1 From Greek diaphrassd, to divide by a partition. 2 From Greek gastér, the stomach. 
e 
