320 FUNCTIONS OF THE NERVOUS SYSTEM. 



The act of Vomiting has been proved to be excitable by impressions trans- 

 mitted through the Gastric branches of the Par Vagum ; although they con- 

 stitute by no means the only channel, through which the various muscles con- 

 cerned in it may be called into combined action ( 505). 



413. The question -of the influence of the motor fibres of the Pneumo- 

 gastric, upon the muscular walls of the stomach, has been already in part dis- 

 cussed ( 387). Although it seems unquestionable that they have the power 

 of stimulating these muscles to contraction, yet there is evidence that the 

 movements of the stomach, which are most essential to digestion, may take 

 place without it. Thus Dr. Reid found, in several of his experiments, that 

 food was not only digested in the Stomach, but propelled into the Duodenum, 

 subsequently to the operation. It seems very probable, however, that a tem- 

 porary suspension of these movements (as of other independent functions of 

 the stomach) may be the first effect of the operation. 



414. It is necessary here to stop to notice, on account of the currency 

 which it has obtained, the doctrine of Dr. Wilson Philip ; that the Par Va- 

 gum controls the secretion of the Gastric fluid ; and that its division checks 

 the secretion. He further stated, that the influence of Galvanism propagated 

 along the nerve, would re-establish the secretion. This statement has been quoted 

 and re-quoted, as an established physiological position ; and, when united with 

 the well-known fact, that galvanism would excite muscular contraction, it has 

 seemed to Dr. W. Philip and other physiologists sufficient to establish the 

 important position, that galvanism and nervous influence are identical. It has 

 been disputed, however, by many other experimenters ; who have satisfied 

 themselves that the secretion of gastric juice continues after the operation; 

 and consequently, that the elaboration of this product cannot be dependent on 

 nervous influence supplied by the Par Vagum, though doubtless in part regu- 

 lated by it. The first effects of the operation, however, are almost invariably 

 found to be vomiting (in those animals capable of it), loathing of food, and 

 arrestment of the digestive process ; and it is not until after four or five days, 

 that the power seems re-established. In the animals which died before that 

 time, no indication of it could be discovered by Dr. R. ; in those which survived 

 longer, great emaciation took place ; but when life was sufficiently prolonged, the 

 power of assimilation seemed almost completely restored. This was the 

 case in 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 intes- 

 tinal 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 obtained 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. 



[M. Bernard has instituted fresh experiments to determine this still-debated question, 

 ninking use of the artificial fistulous openings into the stomach, invented by M. Blondlot. 

 A dog's digestion had been thus watched for eight days, and had always been well effected. 

 On the ninth day, after a day's fast, M. Bernard sponged out the Stomach, which contracted 

 on the contact of the sponge, and at once secreted a large quantity of gastric fluid ; he then 

 divided the pneumogastric nerves in the' middle of the neck, and immediately the mucous 

 membrane, which had been turgid, became pale, as if exsanguine, its movements ceased, 

 the secretion of gastric fluid was instantaneously put a stop to, and a quantity of ropy neutral 

 mucus was soon produced in its place. Al'ter this, no digestion was duly performed, and 

 milk was no longer coagulated; raw meat remained unchanged, and the food (meat, milk, 

 bread and sugar, which the dog had before thoroughly digested) remained for a long time 



