INTESTINAL CONCREMEXTS. 501 



bran is an important food, we often find in the large intestine balls similar 

 to the so-called hair-balls (see below). Such calculi contain calcium 

 and magnesium phosphate (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-fibres, and termed hair-balls. The so-called 

 "jBGAGROPiL-ae," which occur in the ANTILOPUS RUPICAPRA, belong to this group, 

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



The so-called oriental bezoar-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 LITHOFELLTC 

 ACID, C 2 oH 36 O 4 , 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 C U H 6 O 3 , 

 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 problem of digestion consists in part in separating the valuable 

 constituents of the food from the useless ones and dissolving or trans- 

 forming them into forms which are adapted for the processes of absorp- 

 tion. 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. 



Before we can answer the question as to the form in which the pro- 

 teins are absorbed from the intestinal canal, it is of interest to learn 

 whether the animal body can, perhaps, also utilize such protein as are 

 introduced intravenously, subcutaneously, or into a body -cavity, i.e., 

 evading the intestinal canal, or, as OPPENHEIMER calls it, parenteral. 



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



