540 MECHANISM OF SECRETION OF GASTRIC JUICE. 



current, there results a flow of gastric juice. A certain interval occurs 

 before the secretion is manifest, which is to be referred to changes 

 actually taking place in the epithelium of the stomach. The character 

 of the secretion varies according to the stage of the digestive act and the 

 nature of the food. This will be again referred to in a later section. 



It must be mentioned that some observers have not had the same success 

 in showing the secretory importance of the vagus nerve. That certain differ- 

 ences are perceptible in consequence of its excitation, they admit, but they 

 refer the variations rather to the altered power of muscular contraction 

 possessed by the stomach. Thus Leubuscher and Schafer 1 experimented 

 both upon rabbits and dogs, performing the operations according to Pawlow's 

 method. They frequently used a control animal for precision in estimating 

 the change. As far as variations in the amount of hydrochloric acid were 

 concerned, they came to the conclusion that there was no constant difference. 

 The stomach they found invariably relaxed, and the food introduced within 

 was, after a prolonged interval, found to be arranged in two zones, one against 

 the walls of the stomach, which was well digested and contained hydrochloric 

 acid in normal amount, that occupying the centre of the viscus being poor in 

 acid and rapidly becoming decomposed. As far as stimulation of the peripheral 

 stump of the vagus was concerned, they did not obtain constant results, but 

 they appear to have adopted the rapidly interrupted current rather than the 

 induction shocks at prolonged intervals used by Pawlow. That the food was 

 not perfectly mixed, is obvious from their experiments. This will probably 

 explain the decomposition occurring ; this change was noticed also by Pawlow to 

 come on a few days after section of both vagi. It is, however, to be noted that 

 they were unable to confirm the passage of secretory impulses along the vagus. 



There exists one observation upon the human being from which it seems 

 that stimulation of the vagus may cause a flow of gastric juice. Regnard and 

 Loye 2 stimulated the vagus in a decapitated criminal some forty-five minutes 

 after death. Numerous drops of gastric juice appeared over the surface of the 

 stomach. This may also, however, have been the result of movements of the 

 stomach, which they observed at the same time to occur. 



The conditions under which local stimulation provokes secre- 

 tion. As already stated, it has been held by many that simple 

 mechanical irritation of the mucous membrane will directly produce a 

 flow of gastric juice. Beaumont 3 showed that mechanical irritation of 

 the mucous membrane caused increased vascularity and the appearance 

 of small drops of gastric juice, and he further pointed out that the effect 

 is confined to the irritated locality, and that the amount of juice secreted 

 is small in quantity. Tiedemann and Gmelin, 4 Heidenhain, 5 and 

 others also state that the secretion is limited. Pawlow 6 states that 

 the amount secreted is practically nothing, when indigestible substances 

 such as pebbles are placed in the stomach. It may therefore be 

 regarded as probably true that any secretion produced by simple 

 mechanical irritation is extremely small, and the existence of this slight 

 secretion in no way suggests that the normal secretion can be looked 

 upon as the result, to any great extent, of such stimulation. On the 

 other hand, stimulation by food, even if solid, is much more effectual. 



1 ' ' Ueber die Beziehungen des Nervus Vagus zur $alzsaure-secretion des Magenschleim- 

 haut," CentralU. f. inner e Med., Leipzig, 1894, Bd. xv. 



2 "Recherches faites a Amiens sur les restes d'un supplicie," Compt. rend. Soc. de biol., 

 Paris, 1887. 



3 Op. cit. 4 Op. cit. 5 Arcli.f. d. ges. PhysioL, Bonn, 1879, Bd. xix. 

 6 Address at St, Petersburg. Reported in Brit. Med. Journ., London, 1895, 



