Active Hyperccmia. 



389 



3. The Vaso-constrictor Nerves. 



The vaso-constrictor fibres are supposed to be derived from the cervical 

 sympathetic and run in the hypoglossal nerves : the sympathetic fibres for 

 the muscles of the tongue seem to run, not in the hypoglossal, but in the 

 chorda tympani (Boeke, 1921). 



The right vago-sympathetic trunk was ligatured in the neck, cut below 

 the ligature, and the vagal portion was transected at its emergence from the 

 skull. Faradisation of the peripheral end of the E. sympathetic affected the 

 venous outflow in the manner shown in fig. 1. 



During stimulation the drops are seen to become less frequent and on 

 removal of the stimulus the still further decrease indicates that either the 

 vessels immediately relax and accommodate the first outflow of blood, or there 

 is a marked " after effect " following the stimulus. 



Faradisation of the hypoglossal nerve in the curarised animal verifies the 

 fact that the vaso-constrictors run in this nerve (fig. 2), as was first clearly 

 shown by Anrep (senior). 



SingleB 'shock lOooKU. 



Sees. 



Fig. 3. 



Stimulation of the made-up hypoglossal nerve with only a single shock (to 

 avoid any appreciable " metabolite " effect) causes an emptying of the 

 collapsible veins and capillaries by simple compression of the contracting 

 skeletal muscle. It is here suggested that the arterioles, by the simultaneous 



