Active Hyperemia. 



397 



correspond to the H-ion concentration. The effect, as they point out, is 

 really produced by CO2 driven off from the bicarbonate of the blood. Acids 

 weaker than C0 2 were inactive. 



Clipoalinffualara t JJ[ \ 





■ ! — — 



CZips\off • ■ ;. ; \ 





. (Linguals intact) 



Fig. 15. 



In order to put this to a more direct and measurable test, 1 c.c. of Einger's 

 fluid containing the substance was slowly introduced through a fine hypo- 

 dermic needle immediately into the lingual artery without occluding it, thus 

 minimising the capacity effect. Plain Einger, sodium bicarbonate, and lactic 

 acid were found to produce a vaso-dilation in the order named (so that the 

 effect of Einger alone must be discounted), but the effect produced by lactic 

 acid was much the largest and most prolonged (fig. 16) and was in all respects 



1 7cc. z%\ lactic acid 

 Unjectedintoling.art? 



Fig. 16. 



NaHC0 3 



7-6% r/Jactkac. 



HT.R.lincr.ait? icc.LeJtli7iij.arty 



Fig. 17. 



