454 OHEMISTR Y OF THE DIGESTIVE PROCESSES. 



absorption in the form of soaps, is that urged by I. Munk, namely, the 

 enormous quantity of alkali which would be required for such a purpose. 

 Munk 1 reckons that to so combine with the fatty acids of 200 grms. of 

 fat, about 40 grms. of sodium carbonate (Na 2 C0 3 ) would be required. 

 Now a dog of 25 kilos, can easily digest from 200 to 350 grms. of fat 

 in twenty-four hours. 2 Supposing only 200 grins, are digested, and that 

 all this is absorbed as soaps and glycerin, about 40 grms. of sodium 

 carbonate will be required for the purpose ; now the total blood only 

 contains, in such an animal, alkali equivalent to 6 grms. of Na 2 C0 3 ; if 

 the other fluids of the body be supposed to contain an amount of alkali 

 equivalent to another 6 grms. of sodium carbonate, the total alkalinity is 

 equivalent to that of 12 grms. of sodium carbonate. 3 Therefore, to 

 suffice for the absorption of the fatty acids as soaps, from three to four 

 times the total alkali of the body must pass out in the intestinal 

 secretions, and be reabsorbed with the fatty acids, during twenty -four 

 hours. This is obviously impossible ; therefore the fats are not absorbed 

 as soaps and glycerin. 



This objection of Munk loses, however, most of its weight, when 

 the probable processes taking place, in case fats are absorbed as soaps 

 and glycerin, and synthesised again to neutral fats in the epithelial 

 cells, are carefully considered. In the synthesis of fat from soap and 

 glycerin within the cell, alkali is again set free in exactly equal amount 

 to that in which it was used up in the intestine, and this alkali must be 

 got rid of by the cell in some manner. Why should it not be sent back 

 again into the intestine, and act as a carrier to a fresh quantity of fatty 

 acid as soap into the cell ? In such a fashion a very small amount of 

 alkali would suffice to explain the carriage of all the 200 grms. of fat as 

 dissolved soap and dissolved glycerin into the epithelial cells. 



It might possibly be further objected that soaps are only present in 

 small quantity in the intestinal contents. But this applies also to 

 alkali albumin, propeptones, peptones, and sugars ; in fact, to all the 

 products of the digestion of both proteids and carbohydrates. If soaps 

 are normally absorbed by the epithelial cells, it is probable that these 

 cells possess a selective capacity for soap absorption, as they do for many 

 other products of digestion, and hence that the soaps are absorbed as 

 they are formed, and never allowed to accumulate in appreciable 

 quantity in the intestine. 



There is, then, no proof that soaps cannot be formed in the intestine, 

 nor is there any impossibility or improbability in the way of all the fats 

 being first decomposed into fatty acids, then converted into soluble 

 soaps and absorbed as such. 



Theory of absorption as dissolved fatty acids. Another theory is, that 

 the fats are absorbed in the form of dissolved fatty acids. 



The fatty acids of the fats are practically insoluble in water, but are 

 soluble to a certain extent in bile, the solubility increasing with rising temper- 

 ature. Strecker 4 stated, in 1848, that taurocholic acid possesses the property 

 of dissolving fat, fatty acids, and cholesterin in considerable quantity. This 

 fact is mentioned by Strecker in connection with the difficulties attending the 



1 Virchows Archiv, 1880, Bd. Ixxx. S. 11 ; 1884, Bd. xcv. S. 408. 



2 Pettenkofer and Voit, Ztschr. f. BioL, Miinchen, 1873, Bd. ix. S. 30. 



3 These figures must only be taken as argumentative data, overstepping the truth, and 

 not as truly indicating the total alkalinity. 



4 Ann. d. Chem., Leipzig, 1848, Bd. Ixv. S. 29. 



