STOMACH AND INTESTINE. 



399 



oily substances when reduced to an artificial 

 emulsion, would seem to be one of the chief 

 offices of the pancreatic juice. 



The evidence adduced by Bernard* in sup- 

 port of his views appears very conclusive. 

 His experiments gave him the means of ob- 

 taining large quantities of pancreatic juice 

 from Dogs. A mixture of this secretion and 

 oil, when shaken together, immediately pro- 

 duced an emulsion of the most intimate kind, 

 such as no other animal fluid which he exa- 

 mined could imitate. A similar emulsion 

 within the body could be seen in the Rabbit, 

 when fed on butter. In this animal, the pan- 

 creatic duct opens into the intestine com- 

 paratively low down. And hence there is, 

 under such circumstances, a long extent of 

 bowel above the orifice of this duct, quite 

 devoid of white chyle ; while below, the lac- 

 teals are distended with this fluid. And, 

 finally, experiments on the healthy animal f, 

 and observations on human disease, tend to 

 establish the same conclusion. Complete 

 artificial obstruction of the pancreatic duct, 

 diversion of its contents from the intestine, 

 and extensive disease of the secretory struc- 

 ture of the gland, alike prevent the forma- 

 tion of white chyle. 



The small quantity of the pancreatic se- 

 cretion would, perhaps, indicate that much 

 of the metamorphosis of starch is effected by 

 the saliva. And, taken in conjunction with 

 the neutral or feebly alkaline reaction of the 

 bile, and the apparently small amount of alka- 

 line intestinal juice, it may at any rate be re- 

 garded as throwing great doubt upon the old 

 theory of a direct neutralization of the acid 

 chyme in the intestinal cavity. 



The precise share taken by the bile in the 

 process of intestinal digestion, is even more 

 obscure than that of the pancreatic fluid. 

 It may probably be stated as follows : 



The bile is not essential to the solution or 

 absorption of any one of the alimentary prin- 

 ciples. Nor, on the other hand, does its pre- 

 sence check the conversion of protein into 

 peptone J, or of starch into sugar. But from 

 the appearance of the faeces in jaundice and 

 biliary fistulae, it would seem that its admix- 

 ture with the food limits and modifies the 



* In a mere enumeration of the chief digestive 

 changes, all controversial discussion would be out 

 of place. I shall therefore content myself with 

 saying, that having seen this eminent physiologist 

 perform ihe more essential of his admirable ex- 

 periments abroad, and repeated some of them at 

 home, I entertain little doubt of their substantial 

 accuracy. And to the ordinary disparity between 

 the value of the negative and positive results of 

 experiment, one may add, that none of Bernard's 

 German antagonists appear to have succeeded in 

 procuring large quantities of the pure secretion. 

 Indeed I think that a detailed criticism of these 

 negative results themselves, would amply justify 

 the retention (for the present) of Bernard's view. 



t The inflammation which sometimes follows 

 these experiments on animals, may hinder the ab- 

 sorption of fat in two ways : either by attacking 

 the substance of the pancreas, or by engaging the 

 tissues of the villi themselves. 



J Compare p. 349., on the action of the intestinal 

 juice. 



putrefaction of its animal constituent, and 

 the acid fermentation of its vegetable por- 

 tions; and thus far aids in its proper assimi- 

 lation. While the constipation generally ob- 

 served in such cases, indicates that the bile 

 is also a stimulus to the muscular action of 

 the bowels. 



The absorption of fatty matter is, however, 

 materially influenced by the bile. So that, 

 when this secretion is altogether diverted 

 from its accustomed channel, its absence from 

 the intestinal canal reduces the quantity of 

 fat taken up here to about one-fourth of that 

 normally absorbed. 



The quantity of biliary solids discharged 

 with the faeces is but a very small fraction of 

 that poured into the bowel ; probably not 

 more than T ^th or T V n - And much of this 

 may be regarded as a precipitate ; which is 

 produced, partly by an oxidation of a small 

 part of the biliary fats into resinous matter, 

 and partly by the combination of the fatty 

 acids of the bile with the lime taken in the 

 food. 



The details of the assistance given by the 

 bile to digestion, are very obscure. But as- 

 suming the accuracy of M. Bernard's views 

 with respect to the pancreatic function, we 

 may conjecture, that it is the venous, rather 

 than the lacteal absorption of fat, which is 

 furthered by the hepatic secretion. This view- 

 agrees with the known capacity of the soda 

 in the bile to unite with fatty acids in the 

 form of a soap. And that separation of the 

 neutral fats of the food into acid and base, 

 which would probably precede such a sapo- 

 nification, is sufficiently explained by their 

 sojourn in the intestine at the ordinary tem- 

 perature ; or by the direct effect of this kind 

 which the pancreatic fluid could produce, 

 supposing it not overpowered by the gastric 

 juice. But Bidder and Schmidt offer the fur- 

 ther suggestion, that even neutral fat is aided 

 in penetrating the villus by the moistening of 

 its surface with bile : a view which they 

 confirm from experiments with capillary tubes 

 and dead animal membranes. 



The continuous absorption of these various 

 alimentary principles constitutes the chief 

 share taken by the remainder of the intestinal 

 canal in the function of digestion. And as 

 this absorption requires contact, too rapid a 

 transit of the canal, or too limited an extent 

 of digestive tube to be traversed, present much 

 the same appearances in the food, and produce 

 a very similar effect on the organism. Thus 

 the fasces expelled in intestinal fistula, on 

 the one hand, or in diarrhoea on the other, 

 alike exhibit a large quantity of undigested 

 starch, protein, and fat ; with unabsorbed bile 

 and water. And the fatal exhaustion which 

 often accompanies both* of these states, is 

 evidence of the virtual starvation which may 

 thus be brought about. 



From the little change undergone by pro- 

 teinous substances artificially introduced into 

 the large intestine, as well as from the com- 

 parative development of this part of the canal 

 in the carnivorous and herbivorous classes, we 



