io6 



HUMAN BIOLOGY 



blood; it is an excretion. Although an excretion, it is of use on its 

 way out of the body. It is alkaline and helps to neutralize the acid in 

 the chyme ; it excites the peristalsis, or wavelike motion, of the intes- 

 tines, and it aids the pancreatic juice to emulsify the fats. 



The large intestine, or colon, is about two and one half 

 inches in diameter and five feet long. The small intestine 



joins it in tlie lower rig Jit side of tJie 

 abdomen (Fig. 90). There is a fold, 

 or valve, at the juncture, and just 

 below the juncture there is a tube 

 attached to the large intestine, called 

 the appendix, which sometimes be- 

 comes inflamed, causing a disease 

 called appendicitis (Figs. 90, 98). 

 The appendix is a vestigial (vesti- 

 gium, trace) or rudimentary organ, 

 long since useless. Absorption of 

 the watery part of the food continues 

 in the colon, but the colon secretes no 

 digestive fluid. The undigested and 

 innutritious parts of the food are regu- 



liver, stomach, and in- 

 testines. 



FIG. 99. DIAGRAM OF 

 TRUNK to show the 

 many folds of the PERI- 

 TONEUM supporting the larly cast out of the colon. 1 



tone 1 nm is a membrane with many folds 

 that supports the food tube (Fig. 99). 

 Absorption. - The way in which the various digested 

 foods are absorbed has been stated in several preceding 

 topics. What is the name of the organs of absorption in 

 the small intestine ? Which of the following pass into the 

 lacteals, and which into the capillaries of the portal vein : 

 sugar, digested proteid, emulsified fats ? Water and salt 

 need no digestion, and are absorbed all along the ^food 



1 No truly refined person will allow business, pleasure, haste, or neglect to 

 interfere with regular attention to emptying the colon. This is more neces- 

 sary for real cleanliness than regular baths. 



