STOMACH AND INTESTINE. 



335 



efficacy of such infusions, and especially that 

 of the duodenal membrane, is at least partially 

 explained by the way in which the gastric juice 

 is necessarily diffused, with the food, over the 

 surface of the intestinal canal. 



The effect of the neutral salts on artificial 

 digestion has scarcely been investigated with 

 all the attention it merits. But it appears 

 not improbable that many of these inor- 

 ganic substances assist solution, when present 

 in small quantities, but oppose it when added 

 in excess. This is especially the case with 

 chloride of sodium, the ordinary condiment of 

 mankind and of many animals. The effect 

 of this salt in facilitating the digestion of albu- 

 men, fibrine, and casein, has been verified by 

 Lehmann for the proportion of 1 per cent. 



The effect of alcohol is also regulated by 

 its amount and concentration. Diluted, it 

 seems to have no chemical action whatever. 

 In larger quantities, as before remarked, it 

 precipitates pepsine. And in still greater 

 excess, it permanently destroys all its diges- 

 tive energy. 



The way in which the process of gastric 

 solution, whatever be its nature, is assisted by 

 the minute division of the substances sub- 

 mitted to it, as well as by the movements of 

 the stomach, is too obvious to require any 

 special mention. It only remains to add that, 

 according to Purkinje and Pappenheim, an in- 

 crease in the amount of the atmospheric pres- 

 sure furthers the artificial solution of albumi- 

 nous substances. These observers therefore 

 regard natural digestion as somewhat aided by 

 the pressure of the gastric and abdominal 

 parietes. 



The quantitative relations between this or- 

 ganic principle and the proteinous substances 

 which it dissolves, form a very important sub- 

 ject for inquiry. An exact determination of 

 the quantity of pepsine which these substances 

 require for their solution, would greatly 

 assist us in solving many problems with re- 

 spect to the chemistry of digestion. Or con- 

 versely, a knowledge of the exact numerical 

 details of nutrition, and of the daily gastric 

 secretion, would enable us to calculate the 

 proportionate quantity of pepsine periodically 

 required and used. But it is obvious that 

 such calculations can only confirm direct ob- 

 servations; that they multiply all the known 

 errors of their elements, and neglect their un- 

 known ones. And the estimates derived from 

 actual experiment are very conflicting: if, 

 indeed, they can be considered really compar- 

 able. Thus that precipitation of casein, 

 which is effected by the watery extract of 

 stomach, is producible, according to Mit- 

 scherlich*, by a quantity of pepsine amount- 

 ing to -,^-J^.^th of the milk made use of: 

 while Schwann states a^oo tn to be required. 

 Wasmann found that dilution of the pepsine 

 to ^^oV^jth did not destroy its power of dis- 

 solving coagulated albumen. Frerichs-J- and 



* Bericht, &c. der Akademie der Wissenschaften 

 zu Berlin, 1812, p. 147. et seq. 

 t Op. cit. p. 794. 



Schwann give estimates, which (allowing for 

 the impurity of the extract of stomach) may 

 probably be regarded as an assertion, that 

 one part of pepsine will dissolve 500 of meat, 

 or moist and finely divided albumen. With 

 these statements may be contrasted those 

 made by Beaumont, Blondlot, Lehmann, and 

 Schmidt. In describing his observations con- 

 ducted with gastric juice, Beaumont * implies 

 that this secretion cannot take up more than 

 50 per cent, of roast meat. From what he 

 says, however, as well as from some observa- 

 tions by Blondlotf, it seems very doubtful 

 whether even this can be regarded as a per- 

 fect solution. And Lehmann would fix its sol- 

 vent properties at about 25 per cent, for moist 

 albumen. While the average and maximum 

 power of Bidder and Schmidt's pure gastric 

 juice is stated by them at what would be about 

 10 and 20 per cent, respectively for the same 

 substance. Reducing gastric juice to pep- 

 sine in accordance with their analysis, it 

 would seem that one part of the organic prin- 

 ciple cannot dissolve more than 12 of albumen. 

 And even Beaumont's highest estimate would 

 but raise these 12 parts of albumen to 30 of 

 the more digestible meat : a quantity which 

 is still small enough to form a striking con- 

 trast with the larger proportion deducible 

 from the statements of Frerichs. But it is 

 scarcely necessary to observe, that the stale 

 of the substances used, the dilution of the 

 fluid, and the amount of acid, will always ex- 

 ercise a great influence on the results ; and 

 may at least partially account for these great 

 discrepancies. 



As already implied, the gastric juice is ca- 

 pable of dissolving, not only albumen, but the 

 protein-compounds generally, including in this 

 term the various substances known by the 

 names of fibrin, casein, globulin, vitellin, 

 hcematin, &c. To these we may add gelatin, 

 chondrin, and gluten. In the case of all these, 

 however, their physical condition seems greatly 

 to regulate the rate of the process : density and 

 bulk rendering it very slow ; while, conversely, 

 it is accelerated by minute division. Nor 

 is it impossible that the quantities of the sol- 

 vent required vary with the nature and aggre- 

 gation of the particular substance. But in 

 any case the ultimate effect is the same the 

 production of a complete solution. 



The application of the term "chyme," by the 

 older authors, to the food which had undergone 

 stomach-digestion, sufficiently indicates that 

 the mass possesses a comparatively uniform 

 physical appearance. And even when further 

 observation pointed out, that the chyme was 

 liable to considerable variations in colour and 

 consistence, the above opinions as to its uni- 

 formity required but a partial modification. 

 For physiologists then began to be aware, 

 that the gastric change was not so much a 

 stage in the digestion of the whole of the 

 food, as the solution of a certain class of its 



* Op. cit. p. 133. 

 t Op. cit. p. 264, 



