382 INTERNAL SECRETIONS OF PANCREAS AND SPLEEN. 



nerves gave only negative results. Lately, however, Pawlow 

 and some of his students have been able to overcome the 

 technical difficulties in the way, and have given what seems 

 to be perfectly satisfactory proof of the existence of distinct 

 secretory fibers comparable in their nature to those described 

 for the salivary glands. The results that they have obtained 

 may be briefly stated as follows: Stimulation of either the vagus 

 nerve or the sympathetic causes, after a considerable latent 

 period, a marked flow of pancreatic secretion. The failure of 

 other experimenters to get this result was due apparently to 

 the sensitiveness of the gland to variations in its Nood-supply. 12 

 Either direct or reflex vasoconstriction of the pancreas pre- 

 vents the action of the secretory nerves upon it. Thus, stim- 

 ulation of the sympathetic gives usually no effect upon the 

 secretion, because vasoconstrictor fibers are stimulated at the 

 same time; but if the sympathetic nerve is cut five or six days 

 previously, so as to give the vasoconstrictor fibers time to de- 

 generate, stimulation will cause, after a long latent period, a 

 distinct secretion of the pancreatic juice. A similar result 

 may be obtained from stimulating the undegenerated nerve if 

 mechanical stimulation is substituted for the electrical. The 

 long latent period elapsing between the time of stimulation 

 and the effect upon the flow is not easily understood." 



If the innervation of the stomach as we have interpreted 

 it is recalled, Howell's lines furnish several confirmatory data. 

 The fact that "stimulation of the medulla was known to in- 

 crease the flow of pancreatic juice" suggests that our previous 

 association of the vasomotor with the general motor system 

 (sympathetic) was well founded. The vagus being, from our 

 standpoint, the dominating nerve during pancreatic activity, 

 as it is in the case of the stomach, it must also have been 

 stimulated by its center at the proper time. Hence the secre- 

 tion. That the vagus, as we have stated, assumes charge only 

 during functional activity is further sustained by the state- 

 ments that "stimulation of the sympathetic gives usually no 

 effect upon the secretion" . . . "but if the sympathetic 

 nerve is cut five or six days previously, so as to give the vaso- 



12 All italics are our own. 



