THE ALIMENTARY CANAL 377 



tion of fat-laden leukocytes which, by ameboid motion, have found their 

 way into the lacteal. Other fat particles may possibly find their way 

 into the lacteal without the aid of the leukocytes a process which 

 may be more or less dependent upon the vital properties of the lining 

 endothelium. 



The absorption of the products resulting from the digestion of 

 the starches, sugars, albumins, etc., probably proceeds along similar 

 lines. The peptones enter the epithelium in solution and are then 

 secreted, as albumins and globulins, into the tissue spaces, whence they 

 find their way into the lacteals and capillaries. Thus the lacteals 

 become widely distended evn in the absence of the digestion and 

 absorption of fat. 



THE LARGE INTESTINE 



The large intestine includes the cecum, the colon (ascending, trans- 

 verse, and descending portions) and the rectum. It measures about 

 180 centimeters (5 feet) in length, and from 3 inches at the beginning 

 to about l l /2 inches towards the end of the colon. It connects the 

 ileum with the anus. The vermiform appendix represents an atrophic 

 vestige of the terminal portion of the embryonic cecum. 



The three outer coats of this portion of the alimentary canal are 

 identical in structure with those of the small intestine, with a single 

 exception in the irregular distribution of the outer layer of the mus- 

 cular coat, which in the large intestine forms three distinct longitudinal 

 bands or thickenings, the tenice (linece] coli. At other parts of the 

 circumference of the organ the outer muscular layer is slightly thinner 

 than in the small intestine. 



Since the tenia? are shorter than the other coats of the colon, they 

 produce a succession of sacculations or liaustra the boundaries of which 

 are marked internally by crescentic folds, involving the entire wall, 

 the plicce semilunares. These sacculations furnish conspicuous external 

 marks by which the large can be differentiated macroscopically from 

 the small intestine. Another differential characteristic of the colon 

 is the presence generally of fringes and bags of adipose tissue attached 

 along the median border to the serosa, the appendices <'j>i/>loic(v. 



The Mucous Membrane. The mucous membrane of the large in- 

 testine may be best described by comparison with that of the small 

 intestine. If the mucosa of the latter organ be considered to contain 

 two zones, a superficial layer of villi and a deeper glandular layer, that 

 of the large intestine may be said to consist of only the deeper of these 



