Active Hyperemia. 



399 



as by stimulating the peripheral end of the divided hypo-glossal (figs. 19 

 and 20). 



A large number of experiments was performed in the attempt to analyse 

 the muscular contractions of the tongue during swallowing, elicited by 

 stimulating the central end of the superior laryngeal nerve. The resulting 

 vaso-dilation was inappreciable, since the long period of rest between successive 

 swallowings (5 seconds or more), allowed of the complete removal of meta- 

 bolites; and, on the other hand, section of both lingual nerves made no difference. 



In the absence of any definite evidence for a reflex excitation of the lingual 

 nerve, we must examine the metabolite hypothesis as a complete explanation 

 for the hyperemia of muscular activity. We have seen that lactic acid 

 injected into the lingual artery can produce a typical vaso-dilation. Is lactic 

 acid produced in appreciable amount during muscular activity ? The answer 

 is in the affirmative, if, in Byffel's method (1909), it is really lactic acid which 

 is being determined ; estimations by this method gave the following results : — 



Fig. 19. 



Fig. 20. 



Lactic acid in mgrm. per 100 c.c. lingual blood 

 during stimulation of 



Lingual nerve. 



Hypoglossal nerve. 



Dog 11 



6 



40--8 



25 - 6 (3 rains, later). 

 53 -6 



48/0 (1 rain, later). 



12 



13 



16-0* 



64-0 



14 



8-4 



40-8 



Mean 



9 -2 



49 8 



* After resuscitation from temporary asphyxia. 



VOL. XCIII. — B. 



