NERVOUS SYSTEM UPON SECRETION 285 



duct, and then reclosing the intestine, which was only slightly 

 narrowed by this procedure. The small oval patch so removed 

 was then implanted on the outside of the muscular abdominal 

 wall, so that the pancreatic secretion was now poured out to the 

 exterior. 



By careful nursing, adaptation of the food, and administration 

 of sodium bicarbonate so as to make good the loss of alkali due 

 to the flowing away of the secretion to the . exterior, dogs with 

 such fistulae could be preserved alive and in good health for a long 

 time, and after recovery could be used for the study of the effect 

 of alterations in the nature of the food upon the amount and quality 

 of the pancreatic secretion, and for the investigation of the effects 

 of the gland nerves upon the process of secretion. 



In such an animal, the preliminary procedure to studying the 

 effect of stimulation of the vagus upon the secretory process is 

 to dissect out a portion of the nerve in the neck and cut it, attach- 

 ing a ligature to the peripheral end. The nerve is then preserved 

 under the skin for a period of four days, in order to allow time 

 for the cardiac fibres to degenerate. After the lapse of this time, 

 the stitches are removed and the nerve stimulated with slow 

 induction shocks. As a result of stimulating, it is found that 

 after a latent period of about three minutes a flow of pancreatic 

 juice commences and gradually increases in quantity. On stopping 

 the stimulus the flow does not instantly stop, but continues in 

 decreasing quantity for a period of four or five minutes from the 

 cessation of the stimulus. Positive results were also obtained 

 by Pawlow by the use of the so-called " acute " method, provided 

 the spinal cord was cut to avoid reflex inhibition from the operative 

 procedures, and the vagus was stimulated below the cardiac nerves 

 so as not to produce disturbance of the heart and circulation, 

 the order of procedure being tracheotomy, severance of cervical 

 spinal cord below medulla, artificial respiration, opening of thorax 

 and preparation of vagus below the heart, insertion of pancreatic 

 cannula, and slow rhythmic excitation of the nerve. 



In using the acute method, evidence of the presence of inhibitory 

 fibres was obtained similar to that mentioned above in the case 

 of the gastric secretion. Thus it was found that after a steady 

 flow of secretion had been set up by stimulation of one vagus, 

 similar and simultaneous excitation of the other vagus often led 

 after a latent period to a suppression of the flow. 



