394 



Mr. D. T. Harris. 



Functional Activity. 



A plethysmography record of the tongue during the application of a single 

 induction shock to the hypoglossal nerve (fig. 3) shows a simple compression 

 of the collapsible vessels by the contracting muscles and a complete return to 

 normal without any appreciable after effect of vaso-dilation. 



When a tongue is made to develop tension against a muscle lever we note 

 during the application of a series of successive induction shocks (fig. 9) a vaso- 

 dilation which lasts for more than a minute after stimulation (see also Verzar 

 1912). One of the earlier (imperfect) plethysmographic records shows this 

 hyperaemia very well (fig. 10), the vaso-dilation yielding a pulsatile tongue. 



BP 



Myogram 



B.E 



Mperiph. j sec. :wK.U. 



Fig. 9. 



Fig. 10. 



During faradisation of the motor nerve the blood flow is almost completely 

 arrested by the compression of the contracting muscles (fig. 11). It is obvious 



