SECRETION PHYSIOLOGY. 323 



This experiment proves that after each stimulation of the 

 chorda, the thin, chorda sahva filHng the gland ducts is quickly 

 converted, even in the absence of sympathetic influence, into 

 typical viscid, sympathetic saliva.* It shows, also, that the ducts 

 of the normal, resting mucous gland are filled with saliva, sup- 

 posed to be characteristic of the sympathetic' s action. This 

 observation seems to me to render Heidenhain's assumption of 

 special ''trophic" nerve fibres to account for the character of 

 such saliva, superfluous ; and, also, to give additional evidence 

 that sympathetic saliva is nothing more than this " saliva of 

 rest," expelled by compression of ducts and alveoli. The cor- 

 rectness of the latter view is, in my opinion, strongly confirmed 

 by the great variation in character of sympathetic saliva, with a 

 variation of character of the saliva within the gland. 



I wish to point out, also, that the influence of sympathetic 

 stimulation upon the composition of the saliva s'ecreted during 

 coincident stimulation of the dilator nerve, upon which special 

 stress has been laid by Heidenhain, is also readily understood on 

 this hypothesis of the nature of sympathetic action. Langley's 

 discovery'^-' that the sympathetic produces a secretion from the 

 dog's parotid unless the saliva be too thick for expulsion make 

 Heidenhain's results clear.^^ 



Heidenhain found, in harmony with all other observers, that 

 stimulation of the sympathetic usually causes no secretion from 

 the dog's parotid. He concluded from this that the nerve 

 carried no, or few, secretory fibres. f He discovered, however, 

 that if Jacobson's nerve be irritated so as to cause a secretion, 

 and during this irritation the sympathetic be stimulated, the 

 saliva secreted during simultaneous irritation of both nerves was 

 far richer in organic solids than that secreted under the influ- 

 ence of Jacobson's nerve alone. J Denying that the sympathetic 



*This is a pretty conclusive reply to the statement of Heidenhain that the simple 

 contact of the water with thehylogens is not sufficient to dissolve them 

 We have here a demonstration that it is sufficient in the total absence of nerve in- 

 fluence. 



t Heidenhain. Hermann's Handbuch d. Phys. V, p. 55. " Der Sympathicus 

 des Hundes enthalt fiir die Parotis nur trophische, fiir die submaxillaris daneben 

 wenige secretorische Fasern." 



I Heidenhain, Hermann's Handbuch d. Phys. V, p. 55. 



