524 DIGESTION. 



we often find in the large intestine, balls similar to the so-called hair- 

 balls (see below). Such calculi contain calcium and magnesium phos- 

 phate (about 70 per cent), oat-bran (15-18 per cent), soaps and fat (about 

 10 per cent). Concretions which contain very much fat (about 74 per 

 cent) occasionally occur, and those consisting of fibrin clots, sinews, 

 or pieces of meat incrusted with phosphates are also rare. 



Intestinal calculi often occur in animals, especially in horses fed on bran. 

 These calculi, which attain a very large size, are hard and heavy (as much as 8 

 kilos) and consist in great part of concentric layers of ammonium-magnesium 

 phosphate. Another variety of concrements which occur in horses and cattle 

 consists of gray-colored, often very large, but relatively light stones which contain 

 plant residues and earthy phosphates. Stones of a third variety are sometimes 

 cylindrical, sometimes spherical, smooth, shining, brownish on the surface, con- 

 sisting of matted hairs and plant-fibers, and termed hair-balls. The so-called 

 " VEGAGROPIL.E," which occur in the ANTILOPE RUPICAPRA, belong to this group, 

 and are generally considered as nothing else than the hair-balls of cattle. 



The so-called oriental bezoor-stone also belongs to the intestinal concrements, 

 and probably originates from the intestinal tract of the CAPRA .EGAGRUS and ANTE- 

 LOPE DORCAS. There may exist two varieties of bezoar-stones. One is olive- 

 green, faintly shining and formed of concentric layers. On heating it melts with 

 the development of an aromatic odor. It contains as chief constituent LITHOFELLIC 

 ACID, CjJEIseO^ which is related to cholic acid, and besides this a bile-acid, LITHO- 

 BILIC ACID. The others are nearly blackish brown or dark green, very glossy, 

 consisting of concentric layers, and do not melt on heating. They contain as 

 chief constituent ellagic acid, a derivative of gallic acid, of the formula CuHeOs, 

 which, according to GRABBED is the dilactone of hexaoxydiphenyldicarboxylic 

 acid, and which gives a deep-blue color with an alcoholic solution of ferric chlo- 

 ride. The last-mentioned bezoar-stone originates, to all appearances, from the 

 food of the animal. 



Ambergris is generally considered an intestinal concrement of the sperm whale. 

 Its chief constituent is ambrain, which is a non-nitrogenous substance perhaps 

 related to cholesterin. Ambrain is insoluble in water and is not changed by boil- 

 ing alkalies. It dissolves in alcohol, ether, and oils. 



VI. ABSORPTION. 



The contents of the intestine are gradually pushed onward by the 

 peristalsis or rhythmical movement of the intestinal musculature, but 

 the mechanism is not well known. 2 By these processes the intestinal 

 contents are intimately mixed and the constituents of the food which 

 are valuable to the organism are transformed, in the manner previously 

 mentioned, so that they are adaptable for the processes of absorption. 

 In discussing the absorption processes we must treat of the form into 

 which the different foods are changed before absorption, of the man- 

 ner in which this is accomplished, and lastly, of the forces which act 

 in these processes. 

 



1 Ber. d. d. chem. Gesellsch., 36. 



2 See Cannon, Amer. Journ. of Physiol., 6, 12, 29; Magnus, Pfliiger's Arch., 102, 

 103, 108, 111; Baumstark and Cohnheim, Zeitschr. f. physiol. Chem., 65. 



