GASTRIC DIGESTION. 427 



cal properties, so that they for the most part lose their distinctive attributes, 

 and are brought to one uniform condition, that of albuminose ( 167), which 

 seems to be the state best adapted for subsequent assimilation. In this condi- 

 tion they seem to form definite combinations with the solvent fluid, which have 

 received the name of peptones. That these combinations, however, are very 

 different from mere solutions of the same matters in acidulated liquids, has been 

 shown by the experiments of M. Bernard; who found that, on injecting the 

 solution of albumen in very dilute hydrochloric acid into the general circulation, 

 the liquid speedily passed off by the renal secretion; whilst after injecting the 

 solution of albumen in gastric juice, no trace of this could be detected in the 

 urine. Hence it seems evident that the converting power is exerted by the 

 pepsin, or peculiar " ferment" of the gastric fluid, whilst the solvent power is due 

 to the acid; a conclusion which agrees well with that based on other evidence 

 ( 442). It appears from the observations of MM. Blondlot and Bernard, 

 that when liquid Albumen is taken into the stomach, it does not undergo com- 

 plete coagulation before the solvent process commences, but merely becomes 

 opalescent; Casein, on the other hand, is completely coagulated, the peculiar 

 animal principle of the gastric fluid having more power of precipitating it than 

 is possessed by any other reagent ( 22). It is estimated by Lehmann, that 

 about 20 parts of fresh gastric juice (of the dog) are required to dissolve 1 part 

 of albumen; and as the quantity of albuminous matter daily consumed by Man 

 may be estimated at between 3 and 4 oz., it would hence appear that the amount 

 of gastric fluid secreted must be from 60 to 80 oz. This mode of calculation 

 seems to afford the only means of forming even an approximative idea of the 

 quantity of fluid poured forth from the walls of the stomach. Of course by far 

 the larger proportion of this must be re-absorbed, either through the vessels of 

 the stomach itself, or through those of the intestinal canal. The gastric fluid 

 has also a special solvent power for Gelatinous substances; acting upon those 

 which would have otherwise required long boiling for their disintegration. Here, 

 too, the marked difference in action between the gastric juice and a merely aci- 

 dulous fluid, has been demonstrated by M. Bernard; who has shown that, when 

 a piece of bone is submitted to the latter, its mineral portion alone is affected 

 by it; whereas when it is subjected to the former, the gastric juice digests the 

 gelatin, and leaves the phosphates and carbonates unaltered. Here, too, a 

 decided transformation is effected by the operation of the gastric fluid; for the 

 gelatin of the peptone has lost its power of gelatinizing, and is not precipitated 

 by chlorine. 



451. This action of the Gastric solvent upon the azotized constituents of the 

 food, is dependent upon several conditions. One of the most important of these 

 is temperature. A heat of from 96 to 100 is required to keep up the solvent 

 process, which is retarded according to the depression of the thermometer below 

 this standard ; so that at the ordinary temperature of the atmosphere it is com- 

 pletely suspended, to be renewed, however, with an increment of heat. On the 

 other hand, a trifling elevation of temperature above 100 occasions a decom- 

 position in the gastric juice, which entirely destroys its solvent power. The 

 next condition, which specially affects the time required for the process of solu- 

 tion, is motion. This does not act mechanically, by way of "trituration," as 

 was once supposed; for food is found to be digested, when enclosed in metallic 

 balls perforated to admit the access of gastric juice to their interior. But it 

 answers the purpose of thoroughly subjecting the whole of the alimentary 

 bolus to the agency of the gastric solvent, by bringing each part successively 

 into contact with the lining membrane of the stomach from the surface of which 

 the fluid is effused. The removal of the matters already reduced or dissolved, 

 also, has a most important effect in facilitating the solution of the remainder. 

 This removal is due in part to the absorption of the matters in a state of solu- 



