FUNCTIONAL MECHANISM OF THE PANCREAS. 383 



constrictor fibers time to degenerate" . . . '"distinct se- 

 cretion of juice occurs." Inasmuch as the sympathetic fibers 

 are the vasoconstrictors, degeneration annulled their function 

 (limited to tonic vasoconstriction), and the current caused re- 

 action in the only normal nerves that remained, the vagi, 

 which, as we have seen, inosculate with the sympathetic fibers 

 around all vessels, and are the only ones capable of exciting 

 physiological activity. Still, Pawlow obtained secretion by 

 stimulating either nerve. The fact that "a considerable latent 

 period" elapsed before the flow appeared suggests the reason 

 for this; indeed and it is very probable that earlier experi- 

 menters would also have obtained this result had they waited 

 long enough stimulation of either the vagus or the sympa- 

 thetic was transmitted to the solar plexus, and, their own 

 plexuses inosculating over the arteries, the state of functional 

 activity was artificially brought on, though in a slow and de- 

 ficient manner. 



"The secretion is evidently reflex," says M. Duval, "though 

 the nervous channels of this phenomenon are not exactly 

 known; it has been noticed, however, that section of the pneu- 

 mogastrics arrests the secretion of the pancreas." Conversely, 

 "stimulation of the medulla is effective after section of both 

 vagi," according to Foster. The solar plexus forming part of 

 the general motor system (sympathetic), stimulation of the 

 medulla is also transmitted to the pancreas, and the process 

 defined in the last paragraph then prevails. That the blood 

 alone may also sustain the organ's function is shown by the fact 

 that when all its nerves are severed the secretion continues. 

 But, initiated and governed by the vagus, this constitutes what 

 might properly be termed a pseudo-function. 



Eef erring to the blood-vessels, Piersol says: "The larger 

 arterial branches run within the interlobular connective tissue, 

 sending off vessels which pass between the lobules and supply 

 the glandular parenchyma with twigs. These latter enter the 

 lobules and form net-works which inclose the individual acini 

 within the capillary reticulum. The capillaries lie beneath the 

 basement membrane in close relation with the glandular epi- 

 thelium. The veins accompany the arterial trunks within the 

 connective tissue." A similar arrangement prevails in the 



