1042 



PHYSIOLOGY 



the body. There is no doubt however that similar antidromic impulses are 

 involved in the production of the so-called trophic changes, such as localised 



FIG. 475. Effect of excitation of peripheral end of the seventh lumbar posterior 

 root in the dog. (BAYLISS.) 



Uppermost curve, volume of left hind limb; next below, arterial blood 

 pressure ; the third line marks the period of stimulation ; bottom line, time- 

 marking in seconds. 



erythema or the formation of vesicles (as in herpes zoster), which may occur 

 in the course of distribution of a sensory nerve, and is always found to be 

 associated with changes, inflammatory or otherwise, in the corresponding 

 sup. nerve pi ex. 



skin 



art. 



FIG. 476. Diagram to illustrate the production of vaso-dilatation in the area 



of distribution of a sensory nerve. 



prg, posterior root ganglion ; sens.nf, sensory nerve fibre, branching to supply 

 dilator fibres to the skin arteries, and sensory fibres to the skin. 



posterior root ganglion. Moreover evidence has been brought forward that 

 these fibres may take part in ordinary vascular reflexes of the body, that 

 in fact they are normally traversed by impulses in either direction. 



Some observations by Hans Meyer and Bruce tend to indicate that in 

 the antidromic vaso-dilatation, as well as in the reddening and inflammatory 

 changes ensuing on local excitation, we are dealing with axon reflexes, perhaps 



