GASTRIC DIGESTION. 423 



are quite innocuous when administered separately ; but when they are united, a 

 production of hydrocyanic acid takes place ; so th t, if this should occur in the 

 stomach of an animal, the poison proves fatal, provided that it be generated in 

 sufficient quantity. If, however, the emulsin be given first, and the amygdalin 

 half an hour afterwards, no such result occurs ; because the properties of the 

 emulsin are so changed by the gastric fluid secreted during the interval, that it 

 no longer generates hydrocyanic acid with amygdalin. But if the emulsin be 

 given to an animal whose pneumogastric nerves have been just divided, and the 

 amygdalin be administered half an hour subsequently, the effect is the same as 

 if the two substances had been given at one time ; showing that no secretion of 

 gastric fluid could have taken place. The first obvious effects of this operation 

 are vomiting (in animals that are capable of it) and loathing of food ; and the 

 arrestment of the digestive process is indicated, on post-mortem examination 

 some hours afterwards, by the absence of any digestive change in food that may 

 have been taken just previously to the operation, and that has not been ejected 

 from the stomach. 



446. But, as was first proved by Dr. John Reid, 1 a re-establishment of the diges- 

 tive power manifests itself after an interval of some days, if the animals should 

 survive so long. In the animals which died within the first four or five days, 

 no indication of this restoration could be discovered by Dr. R. ; in those which 

 survived longer, great emaciation took place ; but when life was sufficiently pro- 

 longed, the power of assimilation seemed almost completely restored. This was 

 the casein four out of the seventeen dogs experimented on; and the evidence 

 of this restoration consisted in the recovery of flesh and blood by the animals, 

 the vomiting of half digested food permanently reddening litmus paper, the 

 disappearance of a considerable quantity of alimentary matter from the intestinal 

 canal, and the existence of chyle in the lacteals. It may serve to account in 

 some degree for the contrary results obtained by other experimenters, to state 

 that seven out of Dr. R/s seventeen experiments were performed before he ob- 

 tained any evidence of digestion after the operation, and that the four which 

 furnished this followed one another almost in succession ; so that it is easy to 

 understand why those, who were satisfied with a small number of experiments, 

 should have been led to deny it altogether. Another series of experiments was 

 performed by Dr. Reid, for the purpose of testing the validity of the results 

 obtained by Sir B. Brodie, relative to the effects of section of the Par Vagum 

 upon the secretions of the stomach, after the introduction of arsenious acid into 

 the system. According to that eminent Surgeon and Physiologist, 2 when the 

 poison was introduced after the Pneumogastric had been divided on each side, 

 the quantity of the protective mucous and watery secretions was much less than 

 usual, although obvious marks of inflammation were present. In order to avoid 

 error as much as possible, Dr. Reid made five sets of experiments, employing 

 two dogs in each, as nearly as possible of equal size and strength, introducing 

 the same quantity of the poison into the system of each in the same manner, but 

 cutting the Vagi in one, and leaving them entire in the other. This comparative 

 mode of experimenting is obviously the only one admissible in such an investiga- 

 tion. Its result was in every instance opposed to the statements of Sir B. Brodie ; 

 the quantity of the mucous and watery secretions of the stomach being nearly 

 the same in each individual of the respective pairs subjected to experiment; so 

 that their production can no longer be referred to the influence of the Pneumo- 

 gastric nerves. Moreover, the appearances of inflammation were, in four out 

 of the five cases, greatest in the animals whose Yagi were left entire ; and this 



1 "Edinb. Med. and Surg. Journ.," April, 1839.; and "Physiological, Anatomical, and 

 Pathological Researches," CHAP. v. Dr. Reid's results have been confirmed as to this im- 

 portant particular by Hiibbenet (Op. cit.). 



2 " Philosophical Transactions," 1814, p. 102. 



