CONTENTS OF THE LARGE INTESTINE. 563 



as portions of tendon or fascia, and muscular fibres more or less 

 altered, though having escaped complete digestion ; besides this, there 

 are certain earthy salts, especially the ammonio-magnesian phosphate, 

 with the phosphates of magnesia and of lime. The neutral salts of 

 the vegetable acids, such as the citrates, tartrates, malates, and ben- 

 zoates of potash or soda, appear partially in the contents of the lower 

 part of the large intestine, as carbonates, the rest having been absorbed, 

 also, it is said, chiefly in the form of carbonates. Furthermore, the 

 fecal mass contains coloring matters and other substances left from 

 the almost completely changed or decomposed bile, such as cholalic 

 and choloidinic acids, traces of cholesterin, and especially the sub- 

 stance named dyslysin, also a crystallizable substance containing 

 sulphur, named excretine (Marcet), traces of stearic, margaric, and a 

 peculiar fatty acid called excreteric (Marcet), with some animal matter, 

 probably the residue of the pancreatic and the mucous secretions, 

 especially of those of the larger intestine. It appears certain, indeed, 

 that the glandular apparatus of the intestines serves to excrete, and 

 thus eliminate from the blood, products of the decomposition of the 

 tissues, which would be injurious if retained in it ; these must be 

 present in the fecal substance, and may in great part explain its odor. 

 The small intestine, with its villous mucous membrane, is adapted to 

 the function of absorption ; but the non- villous mucous coat of the 

 large intestine appears better adapted for excretory purposes. The 

 percentage composition of the ashes of the daily quantity of feculent 

 matter removed from the body, varies, according to the food, from 2 

 to 10 oz.; the average quantity is about 6 oz., of which three-fourths 

 are water. The percentage composition of the ashes, after burning, is 

 as follows : 



Chloride of sodium, alkaline sulphates, and phosphate of 

 soda (or potash), . . . . . . . . 4 



Phosphate of lime and phosphate of magnesia, . . 81.5 



Sulphate of lime, . . 4.5 



Phosphate of iron, 2 



Silica, 8 



100. 



The contents of the stomach invariably include a certain quantity 

 of atmospheric air (4 nitrogen to 1 oxygen), which has been mixed 

 with the food and saliva in the mouth, and swallowed with them. The 

 decomposition of the amylaceous and saccharine food into lactic and 

 butyric acid, may cause the evolution of carbonic acid and hydrogen. 

 The oxygen, and especially the carbonic acid, being more soluble in 

 water, would be more easily absorbed than the nitrogen and hydrogen ; 

 but the nitrogen may also pass into the blood. An interchange of the 

 other gases with carbonic acid from the blood may take place, by what 

 might be termed intestinal respiration. In the small intestine, the 

 carbonic acid and hydrogen relatively increase in quantity, the nitro- 

 gen remaining about the same; whilst the oxygen disappears. On 

 including a loop of the small intestine of a living animal between liga- 



