182 OF FOOD, AND THE DIGESTIVE PROCESS. 



four hours is about 460 grains, of which only 10 per cent, consists of undi- 

 gested matter. Of the dry faeces, from 23 to 31.5 per cent, (the proportion 

 being highest when an abundant meat diet has been consumed) consists of 

 an inorganic ash ; the composition of which is stated by Enderliu 1 to be as 

 follows : 



Alkaline chlorides and sulphates, 



Bibstsic phosphate of soda, 



Phosphates of lime and magnesia, 



Phosphate of iron, . 



Sulphate of lime, . 



Silica, ..... 



o fiQQ > Soluble in water. 



*J . O rj O J 



80.372] 

 /ror r Insoluble in water. 



I 



7.940J 



The potash generally predominates greatly over the soda, but especially 

 when the diet has chiefly consisted of muscular flesh. The reaction of the 

 Freces is usually acid, but sometimes neutral or alkaline. The study of the 

 composition of the Organic portion of the Fseces is attended with so much 

 difficulty and unpleasantness, that it has hitherto been scarcely prosecuted 

 systematically. According to the inquiries of Dr. Marcet, 2 healthy Human 

 excrements contain, 1. A peculiar substance crystallizing in acicular, silky, 

 four-sided prisms usually grouped into stellse, not subject to spontaneous 

 decomposition, possessing feeble affinities, fusing at about 203 F., contain- 

 ing Sulphur, and having a composition expressed by the formula C^H.^O,,; 

 this he proposes to call Excretin. In infants cholesteriu may take the place 

 of excretin in the Fceces. 3 2. Stearic and Margaric Acids in combination 

 with bases. 3. A coloring matter similar to that of blood and urine. 4. 

 Pancreatin or an analogous form of albumen. And 5. An acid olive-colored 

 substance of a fatty nature, termed Excretolic acid, which is probably united 

 in feces with Excretin or a basic substance closely allied to it. Neither 

 butyric nor lactic acid can be discovered in healthy Human excrement; 

 although the former presents itself in the excrements of Carnivorous Mam- 

 malia, which contain also a substance allied in its nature to excretin, but 

 not identical with it. Dr. Austin Flint 4 has obtained a substance he terms 

 Stercorin ( 56), which results from the decomposition of Cholesteriu, and 

 Vanlair and Masius 5 have isolated a coloring matter which they have named 

 Stercobilin. 6 



129. Of the degree in which the Bile, as a whole, normally enters into 

 the composition of the fteces, it is difficult to speak with precision. Its prin- 

 cipal constituents can be easily recognized in the upper part of the small 

 intestine ; but the further we descend in the intestinal canal, the less of them 

 do we meet with ; and in the contents of the large intestine, and in the 

 evacuated faeces, they are only to be discovered in small quantity. How far 

 this result depends upon their removal from the alimentary canal by reab- 

 sorption, and how far upon the loss of their characteristic properties by de- 

 composition, cannot be stated with certainty. According to Bischoff, Jr., 

 in the human subject about 45 grains of the biliary acids are daily dis- 

 charged by the faeces, whilst, according to Voit's_ estimate, about 170 grains 



' Ann. der Chem. und Pharm., 1844. Porter in do., t. Ixxi, and Fleischmann in 

 Poggendorff's Annalen, 1849. 



* I'ror.M-dings of the Royal Society, June 15th, 1854, and March 12th, 1857. 



3 Marcet, Journ. of Chem. Sue., 1862. 



4 IMiyMolngy of Man, part ii, 1807, p. 309. 6 Centralblatt, 1871, p. 3(10. 



8 Julie, however (Centralblatt, 1871, p. 4(55), regards it as identical with his urobilin. 



