Active Hyperemia. 



391 



It must be acknowledged, however, that the vaso-dilator fibres have a 

 long latent period (5 seconds), time enough to allow of the production of 

 metabolites. To see the drops of venous blood issuing from the Ungual 

 vein suddenly burst into a continuous stream of bright arterial colour on 

 stimulation of the lingual nerve while the tongue remains in a state of 

 restful indifference, is a most simple and convincing demonstration of the 

 individual existence of vaso-dilator nerves. 







vw 





ol. 



, \ Single induction shock 4000 KU. 



Slim. 



Lingual nn (JEcut) 



2 sees. . 



Fig. 6. 







I T. VOij : . ' 



J_ 1 



' • / 

 IZperiph. 





. Tyityg R. Ungual nv. .1 





lOoIUL ., 





Fig. 7. 



Fig. 8. 





Let us examine further the theory which explains vaso-dilation by the 

 action of metabolites. This theory has been based upon the metabolism of 

 the submaxillary gland as measured by its oxygen intake, which is found to 

 be increased in all conditions in which vaso-dilation accompanies excitation 

 of its nerves, and this increased gaseous metabolism only slowly dies down 

 (Barcroft and Kato, 1915). The oxygen consumption in the tongue has been 

 recently measured by Anrep and Evans (1920), and the mean result of their 

 experiments is shown in the following Table. 



