750 



PHYSIOLOGY, EECENT. 



digestion, although that substance may some- 

 times bo found in the course of three quarters 

 of an hour or an hour after the ingestion of 

 food. The acid present was always lactic, 

 even when the conversion of albumen into 

 peptone, and of starch into dextrine and sugar, 

 was distinctly taking place. The observations 

 of Cash, made in Ludwig's laboratory, have 

 shown that, contrary to the statements usually 

 given in text-books, fats may be split up in the 

 stomach into the fatty acids and glycerine, 

 wliile an acid, perhaps the lactic, is formed. 

 It is a remarkable fact that although after the 

 full digestion of every meal a considerable 

 quantity of peptones must be introduced into 

 the blood, none passes off by the kidneys ; yet 

 if solutions of the peptones be directly in- 

 jected into the blood-vessels, from 60 to 70 

 per cent is rapidly eliminated by these organs. 

 Ilofmeister, finding peptone abundant in the 

 wall of the intestine, has arrived at the con- 

 clusion, from his experiments on this point, 

 that the numerous nuclei and cells which oc- 

 cupy the meshes of the adenoid tissue of the 

 intestinal mucous membrane fix the peptones, 

 and thus enable them to enter the blood- 

 current without the danger of being excreted 

 by the kidneys. The white corpuscles, on this 

 view, act as carriers of nutritive material to all 

 parts of the body, just as the red corpuscles 

 act as carriers of oxygen. 



During digestion much saliva, gastric juice, 

 and pancreatic juice flow into the alimentary 

 canal, each secretion bearing with it a con- 

 siderable quantity of ferment, chiefly either 

 amylolytic or proteolytic. Very little, how- 

 ever, is known of the fate of these ferments ; 

 for the little of them that may be found in the 

 faeces and urine makes but a small fraction of 

 the whole amount which is received by the 

 alimentary canal during digestion. Dr. J. M. 

 Langley has made investigations on this sub- 

 ject, the results of which appear to him to 

 show that the amylolytic ferment secreted by 

 the salivary glands is destroyed by the hydro- 

 chloric acid of the gastric juice, that the pro- 

 teolytic and rennet ferments secreted by the 

 gastric glands are destroyed by the alkaline 

 salts of the pancreatic and intestinal juices, 

 and by trypsin, and that the proteolytic and 

 amylolytic ferments secreted by the pancreas 

 are not improbably destroyed in the large in- 

 testine by the acids formed there. In experi- 

 ments with ptyalin, it was found that a ptyalin 

 containing fluid capable of converting a con- 

 siderable amount of starch into sugar in a few 

 minutes is incapable, after treatment at 35 C. 

 with hydrochloric acid of '04 per cent for seven 

 hours, of converting any appreciable amount 

 of starch into sugar in three hours. As in all 

 the animals examined the fluid in the stomach 

 reddened litmus-paper very much more deeply 

 than does hydrochloric acid, the conclusion is 

 drawn that the amylolytic ferment of the 

 saliva is destroyed at any rate by the end of 

 gastric digestion ; and it was corroborated by 



an experiment in which the diluted parotid ex- 

 tract retained but a trace of its amylolytic 

 power when it was warmed for fifteen minutes 

 with one tenth of its bulk of gastric fluid. 

 The destructive action of even very dilute 

 acids was found to be extraordinarily rapid. 

 The secretions from the pancreas and intestinal 

 glands are also capable of dissolving the gas- 

 tric ferments, and owe their power chiefly to 

 their alkaline salts. The action of these salts, 

 as exemplified in sodium carbonate, is decided 

 and rapid. It is augmented when trypsin is also 

 present, but the effect of trypsin alone is less 

 marked. The rennet ferment is, like pepsin, 

 destroyed rapidly at the body temperature by 

 sodium carbonate, and to some extent by tryp- 

 sin; whence we may conclude that it also loses 

 its ferment power irrecoverably in the small 

 intestine. Since trypsin is destroyed both by 

 hydrochloric acid and by pepsin, the adminis- 

 tration of pancreatic extract with food in 

 medical practice to aid digestion is of more 

 than doubtful benefit ; for little, if any, tryp- 

 sin can pass into the duodenum to exercise 

 a digestive function there. An extract of the 

 pancreas rapidly loses its amylolytic power 

 when warmed with dilute hydrochloric acid, 

 more rapidly than does trypsin under similar 

 circumstances, but apparently less rapidly than 

 does the amylolytic ferment of the parotid. 



Eecent researches reported by M. Dufresne 

 throw new light on the relations of ptyalin, 

 diastase, and the gastric juice. It has been a 

 subject of debate whether the saliva is destroyed 

 in the gastric juice, or continues in the stomach 

 its action on starch. M. Dufresne's experi- 

 ments prove that the saliva is paralyzed in pure 

 gastric juice, but recovers its action in the 

 mixed gastric juice and in the duodenum, and 

 is capable of continuing the process of saccb a 

 rification ; while diastase is irrecoverably de- 

 stroyed in hydrochloric solutions or in pure 

 gastric juice, and is profoundly altered after 

 passing into the mixed gastric juice, so that if 

 it still dissolves starch it no longer saccharifies 

 it. Ptyalin is recommended as an excellent 

 re-agent for demonstrating the difference be- 

 tween mixed gastric juice, which owes its acid- 

 ity to organic acids, and pure gastric juice, the 

 strength of which is derived from hydrochloric 

 acid. 



Seegen and Kratschner have brought a few 

 new facts to light from their investigations of 

 the relations of sugar to glycogen in the liver ; 

 and while they find, in accordance with most 

 other observers, that the amount of sugar in- 

 creases after death, they maintain that this 

 increase does not take place, as is generally 

 accepted, at the expense of the glycogen, but 

 of some other substance ; for not only does the 

 quantity of sugar present augment, but a larger 

 percentage of glycogen can actually in some 

 instances be obtained some hours after the re- 

 moval of the liver from the body than instantly 

 after death. If this be true, and glycogen be 

 the result of a process of disintegration, some 



