INTESTINAL DIGESTION. 179 



into grape-sugar. 1 Dobroslawin, 2 pursuing Thiry's method in Dogs, found 

 that the fluid secreted possessed a diastatic action on starch, requiring, how- 

 ever, about two hours to operate, and a slow and feeble action on raw fibrin, 

 which at a temperature of 100 F. was converted into peptone in the course 

 of from 20 to 48 hours, without the occurrence of any putrefactive odor. 

 It had no action on oleaginous compounds. Schiff, 3 also operating after 

 Thiry's method upon Dogs, found that small portions of albumen, casein 

 and fibrin, generally underwent conversion into peptones, and that starch 

 was rapidly converted into sugar. Occasionally, however, perhaps owing 

 to peculiar states of the animal's health, or to the immediate effects of the 

 operation, these actions failed to take place. Quincke 4 also frequently 

 observed the solvent action of the succus eutericus upon fibrin to fail. 

 Lastly, Costa 5 found that in Horses the glycerin extract (v. Wittich's 

 method) of Briinuer's glands, and of the Lieberkiihnian follicles, though 

 capable of converting starch into sugar had no action on albumen or fat. 

 Brucke 6 remarks, that although in normal digestion cane-sugar is converted 

 into grape-sugar, this is effected not by any of the intestinal fluids per se, 

 but by the acids found in the stomach. 



127. Notwithstanding the negative results of some of the above experi- 

 ments, it must be remembered that under normal conditions the fluid of the 

 small intestines is a mixture of the biliary and pancreatic secretions with 

 the salivary and gastric fluids, and with the secretion of the intestinal 

 glandulne, and there can be little doubt that in this part of the alimentary 

 canal all the principal constituents of our food are reduced to a soluble 

 condition. Here the conversion of starchy into saccharine matter is com- 

 pleted, the oleaginous compounds are emulsified and in part saponified, 

 and a powerful solvent agency is exerted even upon albuminous substances 

 which have not been submitted to the previous agency of the gastric fluid 

 (as has been shown by experimentally introducing pieces of meat, through 

 a fistulous orifice, directly into the duodenum), and it thus completes the 

 solvent process which had been very far from perfected in the stomach. 7 It 

 is obvious that the amount of each kind of alimentary substance that can 

 be thus prepared for absorption in a given time, will vary with the amount 

 of the secretion by whose agency this preparation is specially effected ; and 

 as there are many indications that the quantity of each that is taken up in 

 absorption is limited, and that it bears a relation to the wants of the sys- 

 tem, it is probable that the amount of the solvent or reducing fluid secreted 

 by each glandular apparatus, is regulated, as we have seen it to be in the 

 case of the gastric juice ( 110), by the demand set up by the nutrient 

 operations, rather than by the amount of alimentary matter that is waiting 

 to be digested. The processes of digestion and conversion are probably 

 continued during the entire transit of the alimentary matter along the small 

 intestine, and at the same time the products of that conversion are grad- 



1 The infusion of the small intestine of the sheep and calf is incapable of convert- 

 ing cane-sugar into grape-sugar. 



2 Untersuch. aus d. Instit. fur Physiologie in Graz, 1870. Dobroslawin obtained 

 in one case 34 grains of fluid per hour from a loop of intestine about 13 inches in 

 length ; and in another case 28 grains of fluid from a loop about 19 inches in length. 

 The rapidity of secretion was augmented by the passage of a current of electricity. 



3 Abstract in Honle and Meissner's Bericht, 1868, p. 168. 



4 Archiv f. Anat. v. Physiol., 1868. 



5 Centralblatt, 1873, p. 310. 



6 Vorlesungen iib. d. Physiol., 1874, p. 332. 



7 See the account of M. Cl. Bernard's researches in the Amer. Journ. of Med. 

 Sci., Oct. 1851, p. 356; Zander, De Succo Enterico, Inaug. d'ss., Dorpat, 1850; arid 

 Frerichs, art. Verdauung, in Wagner's Handworterbuch, Bd. iii. 



