CRANIAL AND S YMPA THE TIC XER VES. 5 o 7 
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 x 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 via 
versd, were noted by Heidenhain.- 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 — 054 grm. 
saliva, containing 2 - i per cent, of solids. 
(b) Stimulation of the sympathetic for six hours reduced the percentage of 
the chorda saliva from 2 - l to l'O. 
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 winch 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. pkysiol. Inst, zu Breslav., Leipzig, 18(58, S. 71. 
