ii EXTERNAL DIGESTIVE SECRETIONS 111 



e.g. ligamentum nuchae coarsely cut up, there is no secretion in 

 the sac. This only appears when, after such a meal, the animal 

 is given drink, but in this case it lasts a very short time, from 

 1 to 4 hours at most. 



This fact was confirmed by Sanotzsky (1892), who held, like 

 Heidenhain, that it depended on a reflex excitation (other than 

 that of the secretory fibres of the vagus), or on a direct excitation 

 of the secretory gland cells, due to the action of the digestive 

 products absorbed by the walls of the stomach. 



Khizhin (1895) held, on the contrary, that the secretion was 

 due to chemical excitation of the centripetal nerve-endings of the 

 gastric mucosa by certain special foods, previous to their absorption. 

 Direct mechanical stimulation of the mucous membrane also 

 produces secretion, but to a negligible extent. 



There can be no question, as to the gastric secretion being, at 

 least in the first instance, determined by nervous stimuli. On the 

 other hand, the influence on which the continuation of the 

 secretion depends is still debateable. According to Pawlow, it is 

 a chemical action on the peripheral nerve-endings, of the digestive 

 products of the proteins. He observed a profuse secretion when 

 peptones, extract of meat, etc., were introduced into the stomach, 

 without the animal being aware of the same. 



But after Bayliss and Starling published their hormone theory 

 (mentioned above in treating of pancreatic secretion), which 

 obtained a large following, experiments were set going to see 

 whether the same might not hold good for gastric secretion also. 



Edkins (1905) demonstrated that it was possible to extract a 

 substance from the pyloric mucosa which produced a secretion of 

 gastric juice when injected into the circulation, while extract of 

 the mucosa of the fundus had, on the contrary, no effect. 



This substance pre-exists in an inactive state, and becomes 

 active on adding acids, or on boiling (which proves it not to be an 

 enzyme). 



Frouin (1905) noted that the subcutaneous injection of 40 c.c. 

 of gastric juice considerably increased the gastric secretion in dogs 

 with isolated stomachs, from which he deduced the existence in 

 the gastric juice of substances that have the property of increasing 

 the secretory activity of the gastric mucous membrane. 



Without questioning the data cited by these authors, it seems 

 a little premature to use them (with the followers of Bayliss and 

 Starling) as arguments in favour of the hormone theory, which 

 has been shown, in speaking of secretin and the pancreatic secretion, 

 to be ill-founded. 



The amount of juice secreted by the small stomach always bears 

 the same ratio (taking into account the extent of the secreting 

 surface) to the amount secreted by the large stomach, in sham 

 feeding. The degree of acidity, too, is much the same, but the 



