INFL UENCE OF NER VO US S YSTEM. 539 



sequence of psychical conditions, oesophageal fistulse were made, and the 

 saliva was prevented from passing into the stomach. 



In Kichet's l observations on a human subject, who, by swallowing a 

 caustic alkali, had rendered the oesophagus impassable, and in whom con- 

 sequently it had become necessary to make an opening into the stomach, 

 it was observed that chewing savoury food, none of which passed into 

 the stomach, produced a copious flow of gastric juice. It was not 

 possible in these cases to absolutely assert that this resulted from 

 nervous influence acting directly on the secreting epithelium, for move- 

 ments of the stomach may have brought about the flow, but the quan- 

 tity secreted suggested a direct nervous influence. That there is such 

 a direct nervous influence has been conclusively proved by Pawlow, 2 

 in conjunction with Schoumow-Simanowsky. Their experiments were 

 made on dogs which had had a portion of the stomach isolated in the 

 manner already described, care being taken that the nervous connections 

 were intact. In addition, the oesophagus was separated, the cut ends 

 being attached to openings in the neck, so that swallowed food passed 

 out at one opening, and, through the other, food which it was desired 

 should enter the stomach could be passed in. It was possible, therefore, 

 to bring the animal under the influence of food in three ways. In the 

 first place, it might be shown food, but the food would not be actually 

 introduced into the stomach. This constituted the so-called " psychical 

 feeding." 3 Secondly, the animal might be fed by the mouth, but none 

 of the food allowed to enter the stomach, since it would make its exit 

 at the oesophageal opening. This was described as "pseudo-feeding" 

 (Scheinfiitterung). Thirdly, by the introduction of food into the lower 

 division of the oesophagus, true feeding was carried on. The results 

 varied according to the method adopted. The latent period, or period 

 elapsing after administration before secretion commences, is in the dog 

 about seven minutes. This does not vary much whether it be a case of 

 psychical, pseudo-, or true feeding. The latter course of secretion shows, 

 however, considerable variations. This was the first point established 

 by Pawlow. 



He next attempted to discover the paths of the nervous impulses 

 bringing about these changes. Section of the splanchnics did not 

 affect the results, but after severing both vagi the reflex secretion 

 was absent. With one vagus cut (the right), the animal was found to 

 respond in the usual way. Later the left vagus was divided without 

 anaesthesia. The animals live for a few days in this condition, but 

 during this time no reflex secretion occurs. From this it was concluded 

 that the impulses constituting the efferent portion of the reflex act pass 

 along the vagi. But more positive results in this connection were 

 obtained by Pawlow by stimulating the peripheral ends of the cut vagi. 

 If, some twenty-four hours after the second section, the cut end be stimu- 

 lated, and it is better to do this by applying induction shocks at the 

 rate of one per second, rather than by using the rapidly interrupted 



' Le sue gastrique chez 1'honmie et les animaux," Paris, 1878. 



" Die Innervation tier Magendriisen beim Hunde," Arch. f. PhysioL, Leipzig, 1895. 

 3 Though the exhibition of food to the dog, which had been operated on in the manner 

 described above, evoked a flow of gastric juice, if, from previous experience, the dog was led 

 to understand that the food would not actually be given, the secretion very soon stopped. 

 It may be mentioned that Heidenhain did not regularly obtain a floAv as the result of 

 showing the animal food, and this suggests that his method involved interference with the 

 nervous tracts. 



