STOMACH AND INTESTINE. 



.337 



substances which the gastric juice will dissolve. 

 For the more abundant of the salts contained 

 in the gastric juice appear to be almost as 

 closely united to its pepsine as is the acid 

 itself. The supposed complex acid has never 

 been isolated; still less has its combination 

 with the supposed base. The latter, again, 

 does not saturate the acid, and has never yet 

 been replaced by other bases. In like manner, 

 the tolerably fixed proportions of acid and of 

 protein cannot be reduced to definite equiva- 

 lents. And, finally, while the restorative action 

 of fresh acid cannot be fully explained, the 

 equally marked effect produced by pure water 

 is still more mysterious. 



We are thus gradually led to the conclusion, 

 that neither of these four theories solution, 

 combination, contactive excitement, or trans- 

 ferred metamorphosis will afford an adequate 

 explanation of that process of stomach-diges- 

 tion, from the observed phenomena of which 

 they all so widely differ. It is indeed scarcely 

 to be wondered at that we are unable to form 

 a satisfactory theory. For it is probable we 

 are still ignorant of many processes of organic 

 chemistry. While it is possible that the action 

 of the gastric juice is quite sui generis. And 

 hence any view which unites most of the 

 circumstances of the case, will be certainly 

 as useful, and probably as true, as one which, 

 like each of the preceding, assumes an undue 

 parallel for the sake of a full explanation. 



If we must connect the above details by some 

 theory, we may first remark, that the gastric 

 juice dissolves protein-compounds; that it 

 renders them highly soluble ; and that it as- 

 similates their form and reactions to its own, 

 without changing their composition. For any 

 parallel to such a process we can only look to 

 those lower degrees of chemical action, where 

 solution and combination, adhesion and affi- 

 nity, maybe supposed to meet and merge into 

 each other ; where proportions are tolerably 

 definite, but true equivalents indistinct ; and 

 where, though form is changed and reactions 

 modified, elementary composition remains little 

 affected. Actions of such a kind may be 

 found in the union of many substances with 

 water, or its elements, to form the compounds 

 called hydrates. And the conversion of pro- 

 tein into peptone, by the gastric juice, pre- 

 sents so many analogies to the formation of a 

 hydrate*, that it seems not impossible the 

 chief office of this secretion maybe, that of ena- 

 bling water to combine with the various mem- 

 bers of the albuminous groups of alimentary 

 substances, in order to their acquiring that so- 

 lubility, and uniformity of constitution, which 

 must probably precede their admission into the 

 current of the blood. To this vague indication 

 of a theory, I will only add, that the mode in 

 which a definite quantity of the organic prin- 

 ciple takes part in such a process cannot even 

 be conjectured. Its action certainly appears 

 no way comparable to the effect of diastase 

 on starch, or of emulsine on amygdaline. It 

 seems to be an assimilation, in the strictest 



* Compare Dr. Front's treatise "On Stomach 

 and Renal Diseases," 5th edition, p. 470. et passim. 



chemical sense. It is not impossible that the 

 acid commences the process by a slight, 

 though genuine, solution of the more resist- 

 ing substances. And at any rate, this con- 

 stituent seems to have the power of checking 

 putrefaction, if not of arresting all metamor- 

 phosis, in the other ingredients of the secre- 

 tion : like the small quantity of oil of vitriol 

 which is added by the chemist to hydrocyanic 

 acid with the same object. 



Process of secretion. The process by which 

 the gastric juice is secreted from the mucous 

 membrane of the stomach, forms one of the 

 most interesting problems in physiological 

 science ; and one which, if satisfactorily ex- 

 plained, would probably throw much light on 

 the morphology of secretion generally. 



Ever since the discovery of the stomach- 

 tubes by Dr. Sprott Boyd, it has been 

 generally assumed that the secretion of the 

 gastric juice is mainly effected by a discharge 

 of their glandular contents. The precise 

 mode of this expulsion seems usually to 

 have been left undecided : though it has been 

 implied that the pressure of the muscular 

 contractions of the organ upon the more 

 or less solid food would almost compel an 

 evacuation of the tubes. And more recently, 

 Frerichs has asserted that the act of secretion 

 is really aided by such an expulsion ; and that 

 the food becomes enveloped in a layer of the 

 large gastric cells, the discharge of which 

 from the stomach-tubes leaves them collapsed 

 and empty. 



To all of these statements the author ven- 

 tures to offer a deliberate contradiction. In re- 

 searches upon this organ which have extended 

 over some years, he has never seen these 

 gastric cells free from the tubes except when 

 there was good reason to attribute their ex- 

 pulsion to mechanical violence. They are 

 never present in large quantities. In the 

 majority of examinations they are almost 

 absent. With the proper use of the precau- 

 tions previously alluded to, they will rarely 

 or never be found. In addition to this, it 

 may be added, that the arrangement seen 

 in the Dog where the stomach-tubes are 

 lined by a continuous tube of epithelium, which 

 is prolonged into the layer of columnar cellsi 

 that occupies their intervening ridges renders 

 it almost impossible that these cells should be 

 shed in their original form. 



Another part of this statement has already 

 been contradicted. During every stage o'f 

 gastric digestion, the tubes may be seen with 

 precisely the same form, size, arrangement, 

 and contents, which they exhibit during the 

 fasting state. This remark even applies to 

 that narrow calibre of epithelium, which is seen 

 within the axis of the proper gastric tube in 

 the Dog. And hence, ignorant as we are of 

 the exact mechanical arrangement of the 

 fibre-cells at the bottoms of the tubes, still 

 the excessive delicacy of these secreting 

 organs, taken in conjunction with this unU 

 fortuity of appearance, renders it highly im- 

 probable that they are evacuated by any ex 

 traneous pressure. 



