DIGESTION. 



fully established. Of these the most import- 

 "ant is the objection, which has been frequently 

 urged against it, and has perhaps never been 

 satisfactorily repelled, that it is contrary to the 

 ordinary operations of chemical action for the 

 same agent to be able to reduce the various 

 and heterogeneous matters that are taken into the 

 stomach into a uniform and homogeneous mass, 

 and this difficulty is further increased, when we 

 perceive this powerful effect to be produced by 

 a substance possessed of properties apparently 

 so little active as the gastric juice.* 



These objections, and others of an analogous 

 nature, have appeared to many of the most emi- 

 nent modern physiologists to press so powerfully 

 upon any hypothesis of digestion which is derived 

 from either mechanical or chemical principles, 

 that they have conceived it necessary to abandon 

 altogether this mode of reasoning, and have 

 referred it entirely to the direct action of what 

 has been termed the vital principle. It is 

 assumed that the internal coat of the stomach is 

 endowed with a specific property, peculiar to 

 itself, and essentially different from any merely 

 physical agency, by which it acts upon the food 

 and reduces it to the state of chyme. This vital 

 property of the stomach is supposed to be 

 proved, both by the necessity of having recourse 

 to this kind of power, in consequence of the in- 

 adequacy of the ordinary properties of matter, 

 and to be farther confirmed by certain facts that 

 have been supposed to prove that the same 

 substance is differently affected by the gastric 

 juice, merely in consequence of the absence or 

 presence of this principle. Thus it has been 

 observed, that in cases of sudden death, the 

 stomach itself has been partially digested by the 

 gastric juice that was secreted during life,f and 



* Tiedemann and Gtnelin, as the result of their 

 elaborate experimental researches into the nature 

 of the digestive process, conclude that it consists 

 essentially in the solution of the aliment by the 

 gastric juice. Water alone, they observe, at the tem- 

 perature of the mammalia, is capable of dissolving 

 many of the articles employed in diet, and'many 

 which are not soluble in water are so in the" acids 

 which are found in the stomach, and to these they 

 are disposed to refer a considerable part of the 

 operation; Recherches, t. i. p. 363.. 7. We may, 

 however, remark, that a solution of the alimentary 

 matters in water, or even in the acids that exist 

 in the stomach, cannot be supposed to be identical 

 with chyme. 



t This curious fact, which was first announced by 

 Hunter, Phil. Trans, for 1772, p. 447 et seq., and 

 afterwards more fully detailed in his Observ. on the 

 Anim. CEcon. p. 226... 1, has since been fully con- 

 firmed by the observations of some of the roost emi- 

 nent modern anatomists. See particularly Baillie's 

 Morb. Anat. ch. 7. p. 148, 9, and works by War- 

 drop,'v. ii. p. 136, 7, and engrav. to Morb. Anat. fas. 

 3. pi. 7. fig. 2. ; Beck's Med. Jurisp. by Dunlop, p. 

 376. .380 contains many references and good remarks. 

 We have a valuable paper on the subject by Dr. 

 Gairdner, Ed. Med. Chir. Trans, v. i. p. 311 et seq. 

 and also by Dr. Carswell, Ed. Med. Jour. v. xxxiv. 

 p. 282 et seq. ; also Archives de Med. Fev. 1830, 

 and Amer. Jour. Med. Sc. v. vii. p. 227. .9. In the 

 Cambridge Phil. Trans, v. i. p. 287 etseq., we have 

 a case of this description by Dr. Haviland. Dr. 

 Carswell has given an accurate and ample account of 

 the appearances and effects produced by the gastric 

 juice on' the stomach, in the fifth number of his 

 Pathol. Anat. j it is accompanied by two excellent 

 plates. 



upon this principle it has been found, that cer- 

 tain kinds of worms, which exist in the diges- 

 tive organs of animals, are not affected by the 

 gastric juice as long as they remain alive, but 

 that after death they become subject to its 

 action. 



This hypothesis of the vital principle is the 

 one which was supported by Fordyce in his 

 elaborate treatise, and is probably that which, 

 under certain modifications, may be regarded as 

 the prevailing opinion of the modern physiolo- 

 gists. To a certain extent it is correct, and the 

 position on which it is founded, that the living 

 body differs essentially in its powers and pro- 

 perties from the dead body, cannot be denied. 

 But it may still be questioned, whether the ex- 

 planation thus offered be not rather verbal than 

 real, or whether any actual explanation is 

 afforded of the phenomena, or any actual diffi- 

 culty removed by adopting this mode of ex- 

 pression. Every one admits that a living sto- 

 mach differs from one that is deprived of life, 

 but still it remains for us to point out in what 

 this difference consists ; is it a chemical or a 

 mechanical action ? or if it be not referable to 

 either of these actions, to what general principle 

 can it be referred ? It is contrary to the rules 

 of sound reasoning to invent a new agent for 

 the urgency of the individual case, until we are 

 able to demonstrate the absolute impossibility 

 of employing those which were previously 

 recognized. With respect therefore to the 

 hypothesis of the vital principle, as maintained 

 by Fordyce and many of the modern physiolo- 

 gists, we should say, that it is rather a verbal 

 than a real explanation of the phenomena, and 

 that it rather evades the objections than answers 

 them. 



The last hypothesis of digestion which we 

 proposed to notice, that of nervous action, 

 although somewhat allied to the one which we 

 have last examined, is more precise and defi- 

 nite in its statement, and consequently more 

 entitled to our consideration. It assumes, that 

 the process of digestion depends upon the 

 direct and immediate agency of the nervous 

 system. It is founded upon the anatomical 

 fact of the mode in which the stomach is con- 

 nected with the nervous system, and upon the 

 observed relations between those causes that act 

 through the medium of this system, and the 

 changes that take place in the action of the 

 stomach. With respect to the anatomical ar- 

 gument it has been urged, that there is no 

 organ of the body, which is provided with such 

 a number of nerves, proceeding from so many 

 sources, and connected in so direct a way 

 with the cerebral system. There are equally 

 remarkable circumstances of a physiological 

 and pathological nature, which prove the inti- 

 mate connection between the nervous system 

 and the action of the stomach. Not only does 

 the stomach partake of almost every change 

 that occurs, in any part of the corporeal frame, 

 either natural or morbid, in a way which we 

 must conceive can only be brought about 

 through the intervention of the nervous sys- 

 tem, but it is affected by our mental emo- 

 tions, and that probably in a greater degree 

 than any other of our organs, except those that 



