424 OF FOOD, AND THE DIGESTIVE PROCESS. 



seemed to be referable to the longer duration of their lives after the arsenic had 

 been introduced. The results of Sir B. Brodie's experiments may perhaps be 

 explained, by the speedy occurrence of death in the subjects of them, consequent 

 (it may be) upon the want of sufficiently free respiration, which was carefully 

 guarded against by Dr. Reid. 



447. It must be held as demonstrated by these experiments, then, that all 

 the arguments which have been drawn from the effects of lesion of the Pneumo- 

 gastrics upon the functions of the Stomach, in favor of the doctrine that Secre- 

 tion depends upon Nervous agency, must be set aside. That these nerves have 

 an important influence on the gastric secretion, is evident from the deficiency 

 in its amount soon after their section, as well as from other facts. But this is 

 a very different proposition from that just alluded to; and the difference has 

 been very happily illustrated by Dr. Reid. " The movements of a horse," he 

 observes, " are independent of the rider on his back in other words, the rider 

 does not furnish the conditions necessary for the movements of the horse; but 

 every one knows how .much these movements may be influenced by the hand and 

 heel of the rider." It may be hoped, then, that physiologists will cease to 

 adduce the oft-cited experiments of Dr. Wilson Philip, in favor of the hypothesis 

 (for such it must be termed) that secretion is dependent upon nervous influence, 

 and that this is identical with galvanism. Additional evidence of their fallacy 

 is derived from the fact mentioned by Dr. Reid, that the usual mucous secre- 

 tions of the stomach were always found; and they are further invalidated by 

 the testimony of Miiller, who denies that galvanism has any peculiar influence 

 in re-establishing the gastric secretion, when it has been checked by section of 

 the nerves. 



, 448. Our knowledge of the nature of the process of Gastric Digestion has 

 been greatly advanced by recent inquiries; and we are now in a condition to 

 state with considerable precision what it is, and what it is not, the province of 

 the gastric juice to effect. There can no longer be any doubt that the opera- 

 tion is one essentially of chemical solution; and that the vital attributes of the 

 Stomach are only exercised in the preparation of the solvent, and in the per- 

 formance of those movements which promote its action on the alimentary mat- 

 ters submitted to it. The first series of facts which clearly demonstrated this 

 position, were those that resulted from the very pains-taking observations made 

 by Dr. Beaumont, in the case of St. Martin already referred to. By introducing 

 a tube of India-rubber into the empty stomach, Dr. B. was able to obtain a 

 supply of gastric juice whenever he desired it, the tube serving the purpose of 

 stimulating the follicles to pour forth their secretion, and at the same time con- 

 veying it away; and with the fluid thus obtained, he was able to make various 

 experiments, which showed that the change which it effects upon alimentary 

 matter, when it is kept at a temperature of 98 or 100, and frequently agitated, 

 is not less complete than that which takes place when the same matter is sub- 

 mitted to its operation within the stomach, but requires a longer time. This 

 is readily accounted for when we remember, that no ordinary agitation can pro- 

 duce the same effect with the curious movements of the stomach ; and that the 

 continual removal, from its cavity, of the matter which has been already dis- 

 solved, must aid the operation of the solvent on the remainder. The following 

 is one out of many experiments detailed by Dr. Beaumont, " At 11 o'clock, 

 A. M., after having kept the lad fasting for 17 hours, I introduced a gum-elastic 

 tube, and drew off one ounce of pure gastric liquor, unmixed with any other 

 matter, except a small proportion of mucus, into a three-ounce vial. I then 

 took a solid piece of boiled recently-salted beef, weighing three drachms, and 

 put it into the liquor in the vial ; corked the vial tight, and placed it in a sauce- 

 pan filled with water, raised to the temperature of 100, and kept at that point 

 on a nicely-regulated sand-bath. In forty minutes, digestion had distinctly 



