x VASCULAR MUSCLE AND NERVES 351 



There has been much discussion as to whether the sciatic trunk 

 contains vaso- dilator fibres. Goltz and others noted, as the 

 primary effect of dividing the nerve, the atonic dilatation of the 

 vessels in the limb, exhibited principally in the increased 

 temperature of the paw ; while the primary effect of peripheral 

 stimulation is vascular constriction, shown chiefly in the cooling of 

 the same as also by increased blood pressure in the small arteries 

 of large animals (Fig. 160). Shortly after the section of the 

 sciatic, however, the paralysed limb cools off gradually, till at the 

 end of a few days it is colder than the healthy leg, probably because 

 the peripheral ganglia are capable, even when separated from the 

 spinal centres, of recovering their vascular tone until it exceeds 

 the normal. If, when this effect has been produced, the divided 



Fio. 160. Effect upon smallest arteries of posterior extremity of exciting peripheral trunk of left 

 sciatic in horse. (Morat.) A,f, d, pressure in central trunk of right femoral artery ; A,f, s, 

 pressure in peripheral trunk of left femoral artery. Two electric signals record the time 

 in seconds, and the duration of excitation by a tetanising current on the abscissa. Shows 

 that the constriction of the small arteries of a posterior limb hardly increases the central 

 pressure in the femoral of the other limb, while the peripheral pressure in the femoral 

 of the same side, which anastomoses with the small contracting arteries, is conspicuously 

 increased. 



sciatic is again exposed and excited mechanically at the peripheral 

 end, the temperature of the paw rises considerably and exceeds 

 that of the normal side. This shows the presence of dilator fibres 

 in the sciatic, which retain their excitability for a longer time 

 after section than the vaso-constrictors. These results of Goltz 

 were essentially confirmed by the subsequent observations of 

 Ostroumoff, Heidenhain and Griitzner, Kendall and Luchsinger, 

 and others. 



In 1876 v. Frey in Ludwig's laboratory took up Cl. Bernard's 

 studies on the vascular nerves of the subniaxillary gland, and 

 determined the amount of blood which flows out of the chief vein 

 of the glands in the time-unit, when the dilators in the chorda 

 tympani, or the constrictors of the carotid branches of the 

 sympathetic, are separately stimulated; or, lastly, when both 

 kinds of nerves are excited simultaneously. The separate stimu- 

 lation of the two nerves showed that the dilators have a much 



