NERVOUS SYSTEM UPON SECRETION 279 



ing to Pawlow's experiment, is responsible for the greater portion 

 of the flow of secretion. 



The statement that mere mechanical irritation of the gastric 

 mucous membrane by contact with foreign bodies is an efficient 

 stimulus to provoke a flow of gastric juice is so often made in 

 physiological textbooks that it may be well to state that Pawlow 

 entirely denies such an influence, and states that the most thorough 

 and prolonged irritation of the mucous surface, with a glass rod 

 or feather, or by the blowing of sand into the stomach, is incapable 

 of causing a single drop of secretion. 



Another experimental method of great importance devised 

 by Pawlow, both for investigating the effect upon secretion of 

 various forms of foods and for studying the innervation of the 

 glands, was that of forming a miniature stomach completely lined 

 by mucous membrane, and possessing its nerve-supply intact, 

 yet completely shut off from the main stomach. 1 Different foods 

 could be introduced into the main stomach by the usual process 

 of feeding, or, in certain other animals in which the method of 

 operation above described of oesophagotomy and ordinary gas- 

 trotomy had been performed in addition to the formation of the 

 miniature stomach, the food could be introduced directly into 

 the stomach, or psychical or sham feeding could be carried on. 



Since the mucous membrane is not injured in the operation, 

 and the nerve- supply is left intact, the small pouch of mucous 

 membrane isolated becomes a faithful mirror or index of what is 

 occurring in the main stomach. Accordingly the rate of secretion 

 and the quality of the secretion can be studied throughout the 

 whole process of digestion of a meal of any type, and also the 

 innervation of the glands can be tested by observing the effects 

 of section and stimulation of the nerves supplying the stomach. 



We may now return, after the above short sketch of the methods 

 by which Pawlow prepared the stomach for experimentation, 

 and observed the reflex effects of the nervous system upon gastric 

 secretion, to the experiments by which the same observer studied 

 the efferent path in the vagus of the reflex excitation of the 

 secretion. 



As has already been stated, the other functions of the vagus nerve 



1 For the details of this ingenious operation the reader is referred to that 

 most interesting book, " The Work of the Digestive Glands," by J. F. Paw- 

 low, English translation by W. H. Thompson; Griffin, London, 1902. 



