SECRETION OF SALIVA AND GASTRIC JUICE. 267 



minal splanchnic nerves which join the solar plexus (semilunar ganglia) are 

 chiefly composed of medullated fibres, the nerves which pass from the plexus 

 to the stomach are to a large extent composed of non-medullated fibres. 

 All these nerves, both branches of the vagi and those from the solar plexus, 

 lie at first in company with the arteries on the surface of the stomach be- 

 neath the peritoneum. From thence they pass inward, still in company 

 with arteries, and form, on the one hand, a plexus containing nerve-cells 

 between the longitudinal and circular muscular coats corresponding to what 

 in the intestine we shall have to speak of as the plexus of Auerbach, whence 

 fibres are distributed to the two muscular coats ; and, on the other hand, a 

 plexus in the submucous coat, also containing nerve-cells, corresponding to 

 what is known in the intestine as Meissner's plexus. From this latter plexus 

 fibres pass to the mucous membrane ; some of these end in the mascularis 

 mucosse ; whether any are connected with the gastric glands, and if so how, 

 is not at present known. 



There are no facts which afford satisfactory evidence that any part of this 

 arrangement of nerves supplies such a local nervous mechanism as was sug- 

 gested above. The importance, however, of such a local mechanism what- 

 ever its nature, and the subordinate value of any connection between the 

 gastric membrane and the central nervous system, is further shown by the 

 fact that a secretion of quite normal gastric juice will go on after both vagi, 

 or the nerves from the solar plexus going to the stomach have been divided, 

 and, indeed, when all the nervous connections of the stomach are so far as 

 possible severed. And all attempts to provoke or modify gastric secretion 

 by the stimulation of the nerves going to the 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 learned in this matter. 



202. 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 show that the 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 intes- 

 tine, of which we shall speak later on, succeeded in isolating a portion of the 

 fundus from the rest of the stomach ; that is to say, he cut out a portion of 

 the fundus, 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. When 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 fundus 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 mechan- 

 ism of gastric secretion, but we shall have to return to it under another 

 aspect. 



