CRANIAL A AW S YMPA THETIC NER VES. 507 



retarding effect of the sympathetic was due to the secretion produced by it 

 being very thick and viscid, and in consequence blocking up the ducts. 

 Heidenhain l attributed the action of the sympathetic to the lack of oxygen 

 caused by the diminished blood supply. 



The effects on the percentage composition of chorda saliva, caused by 

 first obtaining a considerable quantity of sympathetic saliva, and vice 

 versdj were noted by Heidenhain. 2 He found that protracted stimulation 

 of either nerve diminishes the percentage of organic substance in the 

 secretion subsequently obtained by stimulating the other nerve. 



(a) Thus stimulation of sympathetic for two hours 0*65 grm. of saliva 

 secreted, containing 5 '9 per cent, solids. 



The chorda tympani was then stimulated for two hours. 

 Stimulation of sympathetic for about one and a quarter hours 0*54 grm. 

 saliva, containing 24 per cent, of solids. 



(b) Stimulation of the sympathetic for six hours reduced the percentage of 

 the chorda saliva from 2*4 to I'D. 



Since the organic substance in the saliva comes in the main at any 

 rate entirely, so far as we know from the substance stored up in the 

 gland-cells, the facts given by Heidenhain show that the secretion 

 obtained from the two nerves arises in part at least from the same gland- 

 cells. 



On microscopic examination of the submaxillary gland of the dog, 

 after several hours' excitation, either of the chorda tympani or of the 

 sympathetic, the alveoli are found to be changed to a very unequal degree, a 

 few having still the ordinary resting characters. This renders it probable that 

 the secreting fibres are not equally distributed to all the alveoli. 



Since the sympathetic saliva contains a higher percentage of organic 

 substance than chorda saliva, we should expect that simultaneous stimu- 

 lation of the sympathetic and of the chorda tympani would give a saliva 

 containing a less percentage of organic substance than sympathetic 

 saliva, and a greater percentage than chorda saliva; and this is the 

 case. 



Heidenhain has shown that the chorda saliva which is obtained 

 shortly after stimulating the sympathetic has a higher percentage of 

 organic substance than that obtained before such stimulation. The 

 saliva, however, soon becomes normal, usually after 2 to 3 c.c. have 

 been secreted. The after-effect of sympathetic stimulation is com- 

 parable to the after-action caused by strong stimulation of the chorda 

 tympani, of which we have already spoken (p. 505). 



We have dealt chiefly with the submaxillary gland, but the mutual 

 relations of the cranial and sympathetic nerves are essentially the same 

 in other salivary glands, including the parotid of the dog, in which the 

 sympathetic nerve by itself commonly gives no flow of saliva. 



The following results, taken from experiments by Heidenhain, will serve 

 to illustrate some points regarding the saliva secreted by the parotid gland 

 when both the sympathetic and Jacobson's nerve are stimulated. 



1 Hermann's "Handbuch," Bd. v. S. 46. 



2 Stud. d. physiol. Inst. zu Brcslau, Leipzig, 1868, S. 71. 



