the 



PROPERTIES OF PEPSINE AND OP GASTRIC FLUID. 269 



he matter which has been already dissolved, by its exit through the 

 pylorus, is of course favourable to the action of the solvent upon the 

 remainder. The quantity of food, which a given amount of gastric fluid 

 can dissolve, is limited ; precisely as in the case of the acidulous solu- 

 tion of pepsine. The marked influence of temperature upon its action 

 is shown by the fact, that fresh gastric fluid has scarcely any influence 

 on the matter submitted to it, when the bottle is exposed to cold air, 

 instead of being kept at a temperature of 100. Hence the use of a 

 large quantity of cold water at meal-times, or of ice afterwards, must 

 retard the digestive process. 



473. The pulpy substance, which is the product of the reducing 

 action of the gastric juice, is termed Chyme. Its consistence will of 

 course vary, in some degree, with the relative quantity of solids and 

 liquids ingested. In general it is grayish, semifluid, and homogeneous ; 

 and possesses a slightly acid taste, but is otherwise insipid. When the 

 food has been of a rich oily character, the Chyme possesses a creamy 

 aspect ; but when it has contained a large proportion of farinaceous 

 matter, it has rather the appearance of gruel. The state in which the 

 various alimentary principles exist in it, has not yet been accurately 

 determined ; the following, however, may be near the truth. The Pro- 

 teine-compounds, whether derived from Animal or Vegetable food, are 

 all reduced to a state of solution, if the gastric digestion have been 

 properly performed ; and in this state, they have all the properties of 

 Albumen. Gelatine will be dissolved or not, according to its previous 

 condition ; if it exist in a tissue from which it cannot readily be ex- 

 tracted, it will pass forth almost unchanged ; but when ingested in a 

 state of solution, it remains so ; and if it have been previously prepared 

 for solution by boiling, its solution is completed in the stomach. Its 

 condition, however, is altered in the process ; for it loses the power of 

 gelatinizing, and cannot be precipitated by chlorine ; so that it cannot 

 be detected as such either in the blood or the chyle into which it is 

 received. The Gummy matters of Vegetables are dissolved, when they 

 exist in a soluble form ; as in the case of pure gum, pectine, and dex- 

 trine or starch-gum. It does not appear, however, that any further 

 conversion of Starch is effected by the gastric fluid ; for if no saliva be 

 admitted into the stomach, no sugar is generated there by the meta- 

 morphosis of the starch which it may contain. But the continued intro- 

 duction of the saliva ordinarily occasions the continuance of the process, 

 although the presence of the free acid of the gastric fluid in some degree 

 interferes with it ; and it is not until this has been neutralized by the 

 admixture of the biliary and pancreatic secretions, that the metamor- 

 phosis of the starch is actively renewed. Any sugar that may have 

 been taken in as such, or that may have been produced from starch by the 

 converting power of the saliva, is reduced to the state of complete solu- 

 tion. Oily matters do not appear to be in any way acted upon, other- 

 wise than by being set free by the solution of the envelopes which may 

 have contained them (e. g. fat cells), and by being dispersed through 

 the mass ; their state of division, however, does not seem to be yet fine 

 enough to allow of their absorption. Most other substances, as resins, 

 woody fibre, horny matter, yellow fibrous tissue, &c., pass unchanged 



