CHAPTER XXXIII. 



EXPERIMENT ON THE NORMAL SECRETION OF 

 SALIVA AND GASTRIC JUICE. 



In order to study the secretion of the digestive glands in 

 an unaesthetized normal animal it is necessary by surgical methods 

 to establish permanent openings or fistulse on the surface of the 

 body, through which the secretions may escape. This method has 

 been employed with great profit in the case of several of the glands, 

 the general nature of the experiments being adequately illustrated 

 by observation on the parotid gland (representing a gland with a 

 definite duct) and the stomach (representing a gland which secretes 

 directly on to a mucous surface). The operations necessary to 

 establish the fistula are performed by some competent assistant, 

 and the operated animals are carefully tended so that the wounds 

 heal without suppuration. For successful observations it is 

 furthermore of importance that the animal should become used to 

 the person who is to demonstrate the experiments. 



The Normal Secretion of Saliva. 



METHOD FOR MAKING FISTULA OF THE PAROTID GLAND. A dog is anaesthetised 

 with morphine (morphine hydrochloride 0.01 gm. perkgm. body weight) and finally 

 with chloroform. The mouth is held open by means of a suitable gag and the 

 ductus Stenonianus located (on the mucosa of the cheek opposite the second 

 molar tooth). A small blunt probe is pushed into the duct and the mucous mem- 

 brane around it sponged with sterile surgical gauze. A circular incision is then 

 made through the mucosa around the duct, the area of the circle being a little less 

 than one sq. cm. It will probably be necessary at this stage to suspend further 

 operating for a minute or so in order to administer some more chloroform, and 

 throughout the remainder of the operation similar pauses will occasionally be 

 necessary. The circle of mucosa is then quickly dissected from the underlying 

 tissue up to the duct, after which a stab is made by a fine scalpel through the skin 

 of the cheek opposite the opening of the duct, the edge of the skin incision being 

 trimmed by a scissors so as to make the wound elliptical in shape. By means of 

 a surgical needle a fine silk ligature is passed through the anterior edge of the 

 circle of mucosa and its free ends pulled out through the skin wound. By gentle 



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