26 



DIGESTION. 



by a peculiar state induced on certain of the 

 nerves of the stomach, in the same way that 

 certain nerves of the eye and of the ear receive 

 the impressions of light and of sound. There 

 is, however, this difference between the two 

 cases, that in the instance of the eye and the 

 ear we are able to point out the agent by which 

 the impression is made, whereas we are unable 

 to do this with respect to the stomach.* 



The perception of thirst, although seated in 

 the tongue and fauces, is so intimately con- 

 nected with the state of the stomach, as to be 

 properly referred to our consideration in this 

 place. It is immediately produced by a defi- 

 ciency of the mucous secretion of the part, 

 and consequently must be regarded as ulti- 

 mately depending on a peculiar condition of 

 the glands which secrete this substance. Al- 

 though the sensation of thirst has a less specific 

 character than that of hunger, yet we conceive 

 that it must be referred to a peculiar action 

 induced upon the nerves of the part, in a way 

 analogous to what we suppose to take place 

 with respect to hunger, and like it depending 

 on a peculiar action, the intimate nature of 

 which we are unable to explain .f 



There are various circumstances, which differ 

 much in their nature and origin, acting upon 

 different parts of the system, which all concur 

 in producing a peculiar sensation termed nausea, 

 which is referred to the region of the stomach. 

 It is usually attended with a considerable 

 derangement of all the powers of the body, 

 both muscular and nervous, and if continued, 

 produces the effort to vomit. The act of vomit- 

 ing consists in an inversion of the peristaltic 

 motion of the stomach, commencing at the 

 pylorus, which causes the contents to be carried 

 towards the cardia, and to be forcibly ejected 

 from the oesophagus. It has been generally 

 supposed that the impression which produces 

 nausea, and ultimately vomiting, is in the first 

 instance made on the nerves of the stomach, 

 that it is communicated by them to its muscu- 

 lar fibres, that their action is transmitted, 

 probably by the intervention of the nerves, to 

 the muscles of the abdomen and to the dia- 

 phragm, and that their contraction cooperates 

 with the muscular coats of the stomach in the 

 evacuation of its contents. It has long been a 

 subject of controversy among physiologists in 

 what degree the abdominal muscles assist the 

 coats of the stomach, or how far the latter are 



* See the remarks of Blumenbach, ut supra, 

 21 ; Magendie, Physiol. t. ii. p. 24 et seq. and 

 art. " Digestion," in Diet. Sc. Med. t. ix. p. 370..5. 

 We have some valuable observations by Boerhaave, 

 Praelect. 88. cum notis ; also by Soemmering, 

 Corp. Hum. Fab. t. vi. $ 149.. 56. Haller describes 

 the phenomena of long-continued fasting with his 

 usual minute correctness; El Phys. xix. 2, 3. .7; 

 we have some interesting cases of long-protracted 

 abstinence in Dr. Copland's Trans, of Richerand's 

 Physiol. p. 565 et seq. 



t For an account of the phenomena of thirst, 

 and the explanations that have been offered of 

 them, the reader is referred to Boerhaave, Praelect. 

 $585, 804; Haller, Prim. Lin. $ 639; El. Phys. 

 xix. 2, 9; Blumenbach, Physiol. 330-2, cum 

 notaB; Magendie, Physiol. t. ii. p. 31. .3; Elliot- 

 sou's Physiol. p. 52. 



competent to produce the effect without the 

 aid of the former. Haller supposed that the 

 stomach alone is capable of evacuating its 

 contents,"* while Chirac, Duverney,f and other 

 French physiologists conceived that this organ 

 is entirely passive in the act of vomiting, and 

 the same opinion has been lately maintained 

 by Magendie, and supported by a series of 

 direct experiments. He not only found that 

 vomiting was entirely suspended, when the 

 abdominal muscles and diaphragm were ren- 

 dered incapable of acting upon the stomach, 

 but he even informs us, that when the stomach 

 was removed, and a bladder substituted in its 

 place, vomiting was still induced.^ 



But we are still disposed to believe that the 

 commonly received doctrine is the correct one ; 

 that the action commences in the muscular 

 fibres of the stomach, and is materially assisted 

 by the diaphragm and abdominal muscles. 

 We rest our opinion on the analogy of the 

 other hollow viscera, the uterus, the bladder, 

 and the intestines, where the contraction 

 commences in the organ itself; on the ante- 

 cedent probability, that as the agent which 

 produces the effect is, in most cases, applied 

 to the stomach, it must be supposed to act 

 immediately upon it, and lastly on the mecha- 

 nical nature of the act of vomiting, which 

 appears to be produced rather by a sudden 

 and forcible contraction of the organ itself, 

 than by any external pressure exercised upon 

 it. We conceive also that this view of the 

 subject is confirmed by the effect that succeeds 

 to the division of the par vagum ; it is asserted 

 that when this nerve is divided vomiting can 

 no longer take place, and as it is distributed 

 principally over the stomach, so as to make it 

 appear that this organ is its specific destination, 

 we may presume that the incapacity for vomit- 

 ing depends upon the loss of power in the 

 stomach. 



* El Phys. xix. 4. 12, 14; see also Lieutaud, 

 Mem. Acad. pour 1752, p. 223 et seq. ; Sauvages, 

 Nosol. Meth. t. ii. p. 337. 



t Miscel. Curios. Dec. ii. ant. 4, obs. 125, p. 

 247, 8, and Mem. Acud. pour 1700, hist. p. 27. 

 Nearly the same opinion was maintained by Hun- 

 ter, Anim. CEcon. p. 199, 0. 



$ Mem. sur le vomissement, "p. 19, 2, and 

 Physiol. t. ii. p. 138..40. 



^ Bell's Anat. vol. iv. p. 54 et seq. Legallois and 

 Beclard performed a series of experiments on this 

 subject, which consisted in injecting into the veins 

 a solution of emetic tartar. They particularly 

 attended to the effect produced on the oesophagus, 

 the diaphragm, the abdominal muscles, and the 

 stomach itself; the conclusion which maybe de- 

 duced from these experiments is, that vomiting 

 cannot take place without the compression of some 

 of the contiguous parts upon the stomach ; CEuvres 

 de Legallois, t. ii. p. 91 et seq. Dr. Hall has lately 

 investigated the nature of the connexion between 

 the act of vomiting and the state of the organs of 

 respiration. He conceives that the diaphragm is 

 passive in the operation and that the larynx is 

 closed, and he hence concludes that the muscles 

 of expiration, by their sudden contraction, press 

 upon the stomach and project its contents through 

 the oesophagus ; Quart. Journ. We must conceive, 

 however, that a state of nausea must be, in the 

 first instance, induced, and this must take place 

 through the intervention of the nerves of the 



