518 DIGESTION. 



ERLANGER and HEWLETT 1 found that dogs from which 70-83 per 

 cent of the total length of the jejunum and ileum had been removed, 

 could be kept alive, like other animals, if only the food was not too rich 

 in fat. When the food contained large amounts of fat then 25 per cent 

 was evacuated by the feces as compared to 4-5 per cent in the normal 

 animal. Under these same conditions the amount of nitrogen in the 

 feces was increased to twice the normal amount. 



After the exclusion of the colon in rabbits, BERGMANN and HULT- 

 GREN 2 could find no definite action upon the availability of the cellulose 

 nor could any diminution in the utility of the other constituents of the 

 food be observed. ZUNTZ and USTJANZEW 3 also found that the removal 

 of the caecum had no influence on the utilization of nitrogen; but in 

 respect of other factors they arrived at different results. They found, 

 namely, that the caecum of the rodent is of great importance for the 

 digestion of crude fibre and the pentosans. On feeding hay and wheat 

 to rabbits after the removal of the caecum, the digestion coefficient for 

 crude fibre fell from 42.8 to 23.4-18.7 per cent, and for pentosans from 

 50 to 40-28.7 per cent. 



The question as to the forces which are active in the intestine during 

 absorption has not been answered. It is certain that thus far the laws 

 of diffusion and osmosis alone are not sufficient to explain absorption, 

 although some claim that it is. With all these facts in view, and as 

 it is not within the scope of this book to enter more in detail upon the 

 numerous investigations of this subject, we must refer to larger works 4 

 and to text-books on physiology for further information. 



1 Arner. Journ. of Physiol., 6. 



2 Skand. Arch. f. Physiol., 14. 



3 Verhandl. d. physiol. Gesellsch. zu Berlin, 1904-1905. 



4 See Hober, Physikalische Chemie der Zelle, Leipzig, 1906, and I. Munk, Ergeb- 

 nisse der Physiologic, I, Abt. 1; Hamburger, Osmotischer Druck und lonenlehre, 

 Bd. 2, Weisbaden, 1904. 



