EFFECTS OF NER VES ON THE BLOOD FLO W. 505 



stimulating the cranial nerve, and to become pale on stimulating the 

 sympathetic, 



The more detailed examination 1 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. Von 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 number 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, tlie 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) ; "Le9ons sur les proprieties 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. 



