STIMULA TION OF THE S YMPA THE TIC NER VE. 495 



Eckhard 1 noticed tliat the saliva secreted by the submaxillary 

 gland, on stimulation of the sympathetic, was more viscid and con- 

 tained a higher percentage of solids than that obtained by stimulat- 

 ing the chordo-lingual. 



Neither from the submaxillary, the sublingual, nor the parotid 

 gland of any animal does the sympathetic produce a secretion which 

 approaches in amount that which is produced by the cranial nerve. 

 Unless the gland has been secreting under the influence of the cranial 

 nerve, before stimulation of the sympathetic (cf. p. 496), this stimula- 

 tion causes secretion of a few drops only, and it may be much less. 

 Thus, in the dog, stimulation of the sympathetic for a minute will 

 ordinarily produce two or three drops from the submaxillary gland, and 

 perhaps half a drop from the sublingual. 



In most of the earlier experiments upon the parotid gland of the 

 dog, either no secretion was obtained by repeated stimulation of the 

 sympathetic, or a total amount not exceeding a few drops. This is, 

 however, only a more marked instance of the slow secretion which the 

 sympathetic, after the first few stimuli, causes in the submaxillary and 

 sublingual glands of the same animal. If the parotid gland, after 

 sympathetic stimulation, during which no secretion or a trace only has 

 been obtained, be hardened, and sections be cut, the lurnina, ductules, 

 and duct will be found distended with secretion. 



The maximum total amount of saliva is obtained by stimulating the 

 sympathetic for short periods, with short intervals of rest. Stimulated 

 in this way say, during every other half -minute the sympathetic will 

 give from the submaxillary gland of the dog ^ O tri to ^th of the 

 quantity of saliva that would be obtained by similar stimulation of the 

 chorda tyinpani. 



With protracted stimulation the secretion may continue slowly for several 

 minutes, but sooner or later it stops. Koughly speaking, and within rather 

 narrow limits, the amount of saliva obtained is inversely proportional to the 

 duration of the previous stimulus and directly proportional to the length of 

 the preceding period of rest. After repeated stimulation of the sympathetic, 

 there may be no visible secretion for half a minute to a minute after the 

 beginning of the stimulation, and occasionally the slight secretion which 

 occurs only begins after the stimulation has ceased. 



Heidenhain, stimulating for a quarter of an hour during each half-hour, 

 obtained a secretion from each stimulation for eleven successive hours, i.e.. as 

 long as the experiment lasted. 



In different glands, and in the same gland in different animals, the 

 freedom of secretion of sympathetic saliva compared with that produced 

 by the cranial nerve, and the percentage of organic substance in the 

 saliva, varies considerably. I have already mentioned that the 

 sympathetic causes some secretion from the submaxillary gland, and 

 often none from the parotid. Eelatively, rather more sympathetic 

 secretion is obtained from the glands of the cat and rabbit than from 

 those of the dog. The sympathetic saliva from the submaxillary gland 

 of the dog contains 1 to 3 per cent, of organic substance, that from the 



1 Adrian and Eckhar J, Beitr. z. Anat. u. Physiol. (Eckhard), Giessen, 1860, Bd. ii. S. 83. 

 Bernard, Journ. de I'anat. et physioL, etc., Paris, 1858, tome ii. (1) p. 657, stated that 

 sympathetic saliva was much more viscid than chorda saliva. The sympathetic secretion 

 in the sheep and rabbit was noticed by v. Wittich, Virchow's Archiv, 1866, Bd. xxxvii. S. 93. 



