EFFE CTS OF NER VES ON THE BL OOD FLOW. 505 
stimulating the cranial nerve, and to become pale on stimulating the 
sympathetic. 
The more detailed examination * of the blood flow through the gland 
has been made almost exclusively on the submaxillary gland of the dog. 
The blood flowing ordinarily from the vein is dark ; on stimulating the 
chorda tympani, the blood flow increases rapidly for ten to twenty 
seconds, and then slowly decreases to normal ; the blood itself becomes 
arterial in colour. The degree of the increase naturally varies, the flow 
may be five times as fast as the normal. In favourable cases the vein 
pulsates, and when it is cut the blood issues in jets, somewhat as from 
a small artery. Bernard gives the normal blood flow through the gland 
as about 5 c.c, in a minute ; and this has been approximately the rate of 
flow in my own experiments, in which anaesthetics were given. Yon Frey 
found — presumably in very large dogs — the rate of blood flow through 
the gland to be much greater, about 12 c.c. in a minute. In v. Frey's 
experiments, stimulation of the chorda for ten seconds caused the rate 
of blood flow to be 3 to 7 c.c. in five seconds ; the effect rapidly decreased 
on repeated stimulation ; the flow was diminished by curari. 
There are no complete observations on the changes in the gases of the 
blood as it passes through glands in rest and in activity, but some data are 
given by Bernard. 2 
According to Bidder, 3 the maximal blood pressure in the vein, 
as the result of stimulation of the chorda tympani, is 37 mm. of 
mercury. 
On stimulating the sympathetic the blood becomes darker, and flows 
more and more slowly, the maximal effect being obtained in twenty to 
thirty seconds. 
It is doubtful whether the sympathetic completely stops the blood flow 
in the normal submaxillary gland ; it does so at times in an experiment, but 
this may be due to clotting occurring when the blood becomes slow. In the 
parotid the effect of the nerve appears to be greater. 
The latent period of both chorda and sympathetic varies from a 
barely perceptible time to several seconds ; it depends upon the strength 
of the stimulus, the numl ler of previous stimulations, and other con- 
ditions ; but, generally speaking, the latent period is longer with the 
chorda than with the sympathetic. 
Both nerves have a rather long after-action. The maximal effect 
remains for ten to fifteen seconds, and the original rate of blood flow 
only recurs a minute or so after the end of the stimulation. The dura- 
tion of the after-action depends, up to a certain limit, upon the duration 
of the stimulus; and it appears to be greater with the chorda tympani 
than with the sympathetic. These points, however, have not received 
much attention. 
When both nerves are stimulated simultaneously with maximal 
currents, the sympathetic gets the upper hand during the stimulation, 
1 Bernard, Journ. de Vanat. et physiol., etc., Paris, 1858, tome i. pp. 233, 649 (reprints 
from Compt. rend. Acad. d. sc, Paris, of the same year) ; "Lefons sur les proprtetes physiol., 
etc.," 1859; v. Frey, Arb. a. d. physiol. Anst. zu Leipzig, 1877, Bd. xi. S. 89; Langley, 
Journ. Physiol., Cambridge and London, 1889, vol. x. p. 316. 
2 Cf. "La chaleur animale," 1876, p. 179. 
3 Arch. f. Anat. u. Physiol., Leipzig, 1866, S. 339. 
