404 SECRETION OF GASTRIC JUICE. [BOOK n. 



stomach, have hitherto failed. On the other hand, in cases of gastric 

 fistula, where by complete occlusion of the oesophagus stimulation 

 by the descent of saliva has been avoided, the mere sight or smell 

 of food has been seen to provoke a lively secretion of gastric juice. 

 This must have been due to some nervous action ; and the same 

 may be said of the cases where emotions of grief or anger suddenly 

 arrest the secretion going on or prevent the secretion which would 

 otherwise have taken place as the result of the presence of food 

 in the stomach. !So that much has yet to be learnt in this 

 matter. 



232. The contrast presented between the scanty secretion 

 resulting from mechanical stimulation and the copious flow which 

 actual food induces is interesting because it" seems to shew that 

 tin- secretory activity of the cells is heightened by the absorption 

 of certain products derived from the portions of food first digested. 

 This is well illustrated by the following experiment of Heidenhain. 

 This observer, adopting the method employed for the intestine, 

 of whirh we shall speak later on, succeeded in isolating a portion 

 of the fimdus from the rest of the stomach; that is to say, he cut 

 out a portion of the tundus, sewed together the cut edges of the 

 main stomach, so as to form a smaller but otherwise complete organ, 

 while by sutures he converted the excised piece of fundus into a 

 small independent stomach opening on to the exterior by a fistulous 

 orifice. \Yhen food was introduced into the main stomach secretion 

 also took place in the isolated fundus. This at first sight might 

 seem the result of a nervous reflex act ; but it was observed that 

 the secondary secretion in the fundu^ was dependent on actual 

 digestion taking place in the main stomach. If the material 

 introduced into the main stomach were indigestible or digested 

 with difficulty, so that little or no products of digestion were 

 formed and absorbed into the blood, such ex. gr. as pieces of 

 ligamentum nuchse, very little secretion took place in the isolated 

 fundus. We quote this now as bearing on the question of a 

 possible nervous mechanism of gastric secretion, but we shall have 

 to return to it under another aspect. 



The changes in a gland constituting the act of secretion. 



233. We have now to consider what are the changes in the 

 glandular cells and their surroundings which cause this flow of 

 fluid possessing specific characters into the lumen of an alveolus, 

 and so into a duct. It will be convenient to begin with the 

 pancreas. 



The thin extended pancreas of a rabbit may, by means of 

 special precautions, be spread out on the stage of a microscope 

 and examined with even high powers, while the animal is not only 

 alive but under such conditions that the gland remains in a nearly 



