274 THE ADRENAL SYSTEM AND VASOMOTOR FUNCTIONS. 



prevailing doctrines at once suggests itself: When the gland 

 is in the passive state, the fibers of the chorda tympani "block" 

 the entrance of blood into the organ by causing constriction 

 of the intraglandular arterial subdivisions before the capil- 

 laries are reached; when the gland is to assume the active state, 

 they allow the "block" to relax and a correspondingly greater 

 amount of blood to pass. Indeed, present teachings do not 

 in any way grant constricting powers to the chorda tympani 

 but active dilating properties: i.e., it is thought to actually 

 dilate the vessel by relaxing its muscular coat, the foundation 

 of the belief that vasodilators exist. 



Is such a mechanical dilation of the arteries or arterioles 

 distributed to the gland possible? The intraglandular supply 

 is mainly composed of capillaries, which, of course, have no 

 muscular coat. The smaller arteries or arterioles end as such 

 soon after entering the organ; as the filaments of the chorda 

 tympani follow the course of these vessels we may surmise that 

 their terminal end-plates are attached to the muscle-fibers of 

 the arterioles; but, to avoid any error on this score, we will 

 consider that they end in the muscular layer of "the small 

 arteries" to which Professor Foster refers. Unless we can 

 ascribe to the nerve-endings themselves the lifting power re- 

 quired to relax the vessels, we must depend on some source 

 of expansile elasticity such as that shown to exist in the vessels 

 distributed to muscles, in the elastic festooned layer described 

 by Eanvier. That the vessels are not mechanically disposed so 

 as to forcibly dilate the vascular walls hardly needs mention. 

 Nor does an elastic expansile lamina under the vascular layer 

 exist in these vessels, which, besides their muscular coat, are 

 only endowed with an internal endothelial layer and an ex- 

 ternal adventitious coat. From the standpoint of mechanics, 

 therefore, there is nothing upon which active dilation of the 

 vessels could depend. In the light of the views submitted in 

 this work, therefore, and particularly since the sympathetic 

 and the chorda tympani are merely considered as subdivisions 

 of the one great motor system, we find ourselves obliged to 

 account for the functions of the submaxillary gland with two 

 vasoconstrictor nerves (sympathetic and chorda tympani) and 

 filaments of one of these as the transmitters of inciting and 



