286 ACTION OF NERVES ON THE SECRETION OF SALIVA. 



maxillary and sub-lingual glands, receives fibres from the tympanico- 

 lingual nerve, as well as sympathetic fibres from the plexus on the 

 external maxillary artery. 



Termination of the nerve-fibres. With regard to the ultimate 

 distribution of these nerves we can distinguish (1) the vaso-motor nerves, 

 which give branches to the walls of the blood-vessels; and (2) the secretory 

 nerves proper. Pfliiger states, with regard to the latter, that (a.) 

 medullated nerve-fibres penetrate the acini ; the sheath of Schwann 

 (gray sheath) unites with the membrana propria of the acinus ; the 

 medullated fibre still medullated passes between the secretory cells, 

 where it divides and becomes non-medullated, and its axial cylinder 

 terminates in connection with'' the nucleus of a secretory cell. [This, 

 however, is not proved] (Fig. 116, F). 



(b) According to Pfliiger, some of the nerve-fibres end in multipolar ganglion cells, 

 which lie outside the wall of the acinus, and these cells send branches to the 

 secretory cells of the acini. [These cells probably correspond to the branched cells 

 of the basket-shaped structure.] 



(c) Again, he describes medullated fibres which enter the attached end of the 

 cylindrical epithelium lining the excretory ducts of the glands (E). Pfliiger thinks 

 that those fibres entering the acini directly are cerebral, while those with ganglia 

 in their course are derived from the sympathetic system. 



. [(d) The direct termination of nerve-fibres has been observed in the salivary 

 glands of the cockroach by Kupffer.] 



145. Action of the Nervous System on the 

 Secretion of Saliva. 



A. Sub-maxillary Gland. Stimulation of the facial nerve at its 

 origin (Ludwig and Rahn) causes a profuse secretion of a thin 

 watery saliva, which contains a very small amount of specific consti- 

 tuents (Eckhard). Simultaneously with the act of secretion, the blood- 

 vessels of the glands become dilated, and the capillaries are so distended 

 that the pulsatile movement in the arteries is propagated into the 

 veins. Nearly four times as much blood flows out of the veins (Cl. 

 Bernard), the blood being of a bright red colour, and contains one- 

 third more than the venous blood of the non-stimulated gland. 

 Notwithstanding this relatively high percentage of 0, the secreting 

 gland uses more O than the passive gland ( 131, 1). 



[If a cannula be placed in Wharton's duct, e.g., in a dog, and the 

 chorda tympani be divided, no secretion flows from the cannula. On 

 stimulating the peripheral end of the chorda tympani with an interrupted 

 current of electricity, the same results copious secretion of saliva and 

 vascular dilatation, with increased flow of blood through the gland 



