FUNCTIONS OF THE SALIVARY GLANDS. 275 



regulating impulses. As the three sets of terminal nerves thus 

 originate from the one general system, the same impulses must 

 furthermore satisfy the needs of all three as we ascertained 

 was the case with muscles. 



Before defining the manner in which we interpret the 

 functional process, a few quotations from Professor Foster's 

 work will serve to show that we are probably not on a wrong 

 path. As to dual function of the chorda tympani, he says, 

 referring to a series of experiments reviewed by him: "They 

 further lead us to suppose that the chorda contains two sets of 

 fibers, one of which we may call secretory fibers, acting directly 

 on the secreting structures only; and the other, vasodilator 

 fibers, acting on the blood-vessels only." Again, and what 

 seems to us to be a striking indirect confirmation of our views: 

 "When the chorda is stimulated, there pass down the nerve 

 in addition to impulses affecting the blood-supply, impulses 

 affecting directly the protoplasm of the secreting cells, and 

 calling it into action, just as similar impulses call into action 

 the contractility of the substance of a muscular fiber. Indeed, 

 the two things, secreting activity and contracting activity, are 

 very parallel." 



The functional mechanism of the submaxillary gland, as 

 we view it, is as follows: 



Some fibers of the chorda tympani are distributed to the secret- 

 ing elements to excite and govern their metabolism; the remaining 

 fibers of the same nerve are distributed to some of the glandular 

 arterioles, but not to those which supply capillaries to the secreting 

 elements. While the gland is in the passive state the blood flows 

 equally through all arterioles. 



When the gland is active, the chorda tympani constricts the 

 arterioles to which it supplies fibers, and thus forces the bulk of 

 the blood through the free arterioles and thence into the glandular 

 capillaries. 



The rapidity of the blood-flow through the organ is concur- 

 rently increased through sympathetic constriction of the extra- 

 glandular arterial branches functionally connected with the gland. 



The effect of stimulation of the chorda tympani as noted 

 by Professor Foster now seems clear: "The small arteries of 

 the gland become very much dilated, and the whole gland 



18 



