STOMACH AND INTESTINE. 



349 



impossible that the juice carried onwards 

 into the intestine is there concentrated by 

 the partial absorption of its watery part, some 

 of the strange quantitative results obtained by 

 Bidder and Schmidt cease to be altogether in- 

 explicable. It may indeed be urged, that the 

 alkaline character observed in the intestinal 

 juice sufficiently proves that its digestive pro- 

 perties are not derived from the stomach. 

 But although the addition of a caustic alkali 

 destroys the efficiency of gastric juice, still 

 such a process seems very different from that 

 absorption of acid, or that gradual admixture 

 of a dilute alkaline solution, by which a similar 

 reaction would probably be communicated in 

 the living intestine. And, finally, is it like the 

 ordinary economy of Nature, that an elaborate 

 secretion should pass the pylorus, to be at once 

 annihilated, and then replaced by a second and 

 equally complex antagonist juice ? On such a 

 supposition, indeed, there are many animals in 

 whom almost all the gastric juice would be 

 wasted. For example, there is great reason to 

 suppose that the sojourn of food in the Horse's 

 stomach is so brief, that anything like the 

 stomach digestion of Carnivora is impossible. 

 But are we therefore entitled to assert that 

 this organ is utterly useless? 



Such considerations appear to render it 

 more probable, that the gastric juice may 

 retain its digestive efficacy after passing 

 through the pylorus ; and that the presence 

 of this secretion in the small intestine suffi- 

 ciently explains the solvent powers of the 

 juice which is found in this situation. 



But we are not left to such arguments alone 

 to disprove the solvent powers ascribed to the 

 intestinal juice by the above observers. They 

 receive a still more direct contradiction from 

 the experiments made by Frerichs* and by 

 Lehmann.f These authorities concur to state, 

 that neither in nor out of the body can it 

 dissolve the protein compounds. And Leh- 

 mann's case may be regarded as affording 

 much more than an ordinary negative re- 

 sult ; since in it, all communication between 

 the stomach and the fistulous aperture made 

 use of, seems to have been excluded. 



Finally, we may recall to the reader that 

 close parallel which was observed in the action 

 of the gastric juice and the infusion of sto- 

 mach ; how, allowing for dilution and im- 

 purity, we found the latter behaving just like 

 the former. Now, in striking contrast to this 

 significant fact, numerous observers J agree in 

 representing the infusion of intestine as utterly 

 incapable of that solvent action attributed by 

 Bidder and Zander to its secretion. Indeed, 

 Koelliker and Goll have found the capa- 

 city of digesting protein-compounds so inti- 

 mately connected with the structure of the 

 proper gastric tubes, as to be almost lost in 

 the pyloric extremity of the Dog's stomach ; 

 where these begin to assume the characters 



* Loc. dt. 

 t Is>c. cit. 



I Kotlliker, Valentin, Todd and Bowman, and 

 others. 



of intestinal tubes by losing their oval gastric 

 cells. 



Hence all these circumstances throw great 

 doubt on the alleged solvent powers of the in- 

 testinal juice ; and render it impossible for us 

 at present to decide what is the exact digestive 

 office which it fulfils. And we are almost as 

 ignorant of its quantity as of its quality. But 

 it is probably secreted by the small intestine 

 in much greater amount than by the large. 

 According to Bidder and Schmidt, it is poured 

 out most freely about five or six hours after a 

 meal. And drinking soon increases its amount, 

 without causing any con verse diminution of its 

 concentration. Its strongly alkaline reaction 

 may be conjectured to have some relation to 

 that large quantity of acid, which is appa- 

 rently withdrawn from the chloride of sodium 

 contained in the blood of the stomach, in 

 order to furnish the gastric juice. Indeed, a 

 liberation of soda or some other alkaline base, 

 appears almost implied in that of the hydro- 

 chloric acid. But hitherto no exact analysis 

 has informed us to what particular substance 

 the alkaline character of the intestinal juice 

 is immediately due. And it is only after a 

 careful comparison of the composition and 

 quantity of this secretion with those of the less 

 alkaline bile and pancreatic fluid that we 

 should be entitled to conjecture, how far the 

 neutralization* of the acid peptone constitutes 

 a special function of the intestinal juice. Still, 

 from the great extent of secreting surface 

 which yields this juice, we can hardly doubt, 

 that it takes a large share in this neutralizing 

 process, which was formerly attributed chiefly 

 to the bile. It probably thus forms part of 

 that cycle of alternate decomposition and 

 recomposition, which appears to be under- 

 gone by the chloride of sodium. 



The vascular arrangements by which these 

 intestinal tubes are supplied with blood, so 

 closely resemble those of the stomach -tubes, 

 as to Vender any special description of them 

 superfluous. Like the tubes themselves, the 

 vessels are chiefly concerned with secretion. 

 But while we are left in doubt as to the pre- 

 cise degree or kind of that absorptive function 

 which the vessels of these tubes possess, in 

 common with those of all such mucous sur- 

 faces, we are perhaps justified in attributing 

 a special capacity of absorption to the plexus 

 of large capillaries, which here, as in the 

 former organ, lies immediately beneath the 

 epithelium, around their open extremities. 

 The loops of this superficial plexus are 

 generally more simple than in the stomach. 

 They encircle the mouth of each tube with 

 what is often only a single ring of capillary 

 (b fig. 258.) ; except in the neighbourhood of 

 the solitary or agminate follicles, where they 

 resemble the analogous gastric vessels in 

 forming more complex meshes (a Jig. 20.) 

 They communicate very freely with the capil- 



* It is impossible to state whether this neutra- 

 lization of the gastric acid takes place during the 

 sojourn of the gastric juice in the intestine, or after 

 its absorption into the capillary veins around the 

 canal. 



