58 THE WORK OF THE DIGESTIVE GLANDS. 



with the same object, and yet what we are now able publicly to demon- 

 strate was never seen. The reason of our success lies in the nature 

 of our preparations for the experiment. These specialities are two : 

 The animal is subjected to no painful sensations, and not even nar- 

 cotised, as is the usual custom elsewhere. On the other hand, thanks 

 to the time which has elapsed (four days) since the vagus was divided, 

 all circulatory disturbances are excluded which would otherwise follow 

 the excitation of this nerve. On the fourth day after its section, 

 the cardio-inhibitory fibres, for example, have lost so much of their 

 irritability that the strongest excitation of the nerve is scarcely able 

 to produce even an insignificant and momentary slowing of the heart- 

 beats. In order to comprehend this circumstance it is necessary to 

 remember that the excitability of different nerve fibres disappears 

 after section, with different degrees of rapidity. Thus, in this case the 

 cardio-inhibitory fibres lose their irritability earlier than the secretory 

 fibres for the pancreas. In our experiment, therefore, the glands have 

 neither suffered by the operation nor by the circumstances accompanying 

 the excitation. 



But one can also obtain a positive result with the acute experi- 

 ment, if it be only carried out on a suitable plan. Our procedure 

 is as follows : Tracheotomy is performed as quickly and painlessly 

 as possible ; then the cervical cord is severed from the medulla, occupy- 

 ing only a couple of seconds, after which artificial respiration is set up. 

 And now we may quietly proceed further. The chest is opened in 

 order to seek out the vagi below the heart, and then, after opening the 

 abdominal cavity, a cannula is tied into the pancreatic duct. Under 

 such conditions we are able in every experiment, to observe the secretory 

 effect of the vagus on the pancreatic gland, although we may have to 

 excite the nerve perhaps several times at the beginning of the experi- 

 ment without result. The meaning of the foregoing procedure is at 

 once clear. By division of the spinal cord the harmful inhibitory 

 effects of the exceedingly lengthy operations are prevented, while, by 

 exciting the vagus in the thorax, its influence on the heart's beats is 

 avoided. 



Further investigations carried out in this manner have brought 

 to our notice two conditions under which the secretion of the pancreas 

 may be inhibited by nervous influences. In our own experiments, 

 as well as in those of earlier authors, the pancreas has shown 

 itself to be extraordinarily sensitive to circulatory disturbances. It 

 is only necessary to excite its vaso-constrictors for a short period 

 (two to three minutes), or to compress the aorta for tho same length of 

 time, in order to prevent it for a long time from reacting to a previously 

 effective stimulation of the vagus. From these experiments it can 



