DIGESTION. 



287 



There seems no reason to conclude that any special "secondary diges- 

 tive" process occurs in the csecurn or in any other part of the large intestine. 

 Probably any constituent of the food which has escaped digestion and 

 absorption in the small bowel may be digested in the large intestine; and 

 the power of this part of the intestinal canal to digest fatty, albuminous, 

 or other matters, may be gathered from the good effects of nutrient ene- 

 mata, so frequently given when from any cause there is difficulty in intro- 

 ducing food into the stomach. In ordinary healthy digestion, however, 

 the changes which ensue in the chyme after its passage into the large in- 

 testine, are mainly the absorption of the more liquid parts, and the com- 

 pletion of the changes which were proceeding in the small intestine, the 

 process being assisted by the secretion of the numerous tubular glands 

 therein present. 



Faeces. By these means the contents of the large intestine, as they 

 proceed toward the rectum, become more and more solid, and losing their 

 more liquid and nutrient parts, gradually acquire the odor and consist- 

 ence characteristic of faces. After a sojourn of uncertain duration in 

 the sigmoid flexure of the colon, or in the rectum, they are finally ex- 

 pelled by the act of defecation. 



The average quantity of solid faseal matter evacuated by the human 

 adult in twenty-four hours is about six or eight ounces. 



COMPOSITION OF 



Water 733-00 



Solids 267-00 



Special excrementitious constituents: Excretin, 

 excretoleic acid (Marcet), and stercorin (Aus- 

 tin Flint). 



Salts: Chiefly phosphate of magnesium and phos- 

 phate of calcium, with small quantities of iron, 

 soda, lime, and silica. 



Insoluble residue of the food (chiefly starch grains, 



woody tissue, particles of cartilage and fibrous \ 267*00 

 tissue, undigested muscular fibres or fat, and 

 the like, with insoluble substances accidentally 

 introduced with the food). 



Mucus, epithelium, altered coloring matter of bile, 

 fatty acids, etc. 



Varying quantities of other constituents o.f bile, 

 and derivatives from them. 



Length of Intestinal Digestive Period. The time occupied by 

 the journey of a given portion of food from the stomach to the anus, 

 varies considerably even in health, and on this account, probably, it is 

 that such different opinions have been expressed in regard to the subject. 

 About twelve hours are occupied by the journey of an ordinary meal 



