270 . THE ADRENAL SYSTEM AND VASOMOTOR FUNCTIONS. 



laries in contraction and dilation will now furnish us a clue 

 to the functional mechanism of the organ. 



It seems clear that if, notwithstanding the dilation of 

 the vessels, the glandules did not become active it was because 

 these vessels were not directly connected with them; in other 

 words, because the secretory part of the organ was not situated 

 in the direct pathway of the blood-stream. Under these con- 

 ditions a gland would receive its blood-supply through an arte- 

 rial loop and only become active when the main channel would 

 be constricted. It would bear the same relation to the main 

 blood-path that a side-track bears to the main track of a rail- 

 road. Unused, the side-track typifies the passive state; used, 

 it represents the active state, the latter being assumed when 

 the main track is blocked. Unusual dilation of the main 

 blood-path, under these circumstances, would deplete the 

 gland, if it bore any influence upon it at all; a small dose of 

 pilocarpine, while causing lacrymation in the normal gland, 

 would hardly overcome the excessive vascular dilation of the 

 one on the operated side; a large dose, on the contrary, by 

 increasing general vascular pressure, would so engorge the 

 weakened vessels as to cause excessive lacrymation on the 

 corresponding side, as observed in Onuf and Collins 7 s first two 

 animals. 



The functional mechanism just referred to can be studied 

 with more precision in the next subject to be analyzed. 



THE SALIVARY GLANDS. When the effects of increased 

 blood-supply on the functional activity were reviewed, we saw 

 that when the chorda tympani was stimulated after section 

 the submaxillary gland assumed marked activity; its vessels 

 became greatly enlarged, and its main trunk, which gave 

 passage to blackish blood before the experiment, remained as 

 red as arterial blood as long as the chorda tympani was stim- 

 ulated. Evidently this nerve is the intermediary of the gland's 

 functions, and Professor Foster is inclined to even exclude 

 the sympathetic as an efferent nerve and to assign all the 

 attributes of such a nerve to the chorda tympani. Even from 

 our standpoint this view is tenable, since it not only distributes 

 filaments into the gland, but another besides, which reaches 

 the organ "along the small arteries" distributed to it. To the 



