NERVOUS CONTROL OF THE BLOOD-VESSELS 1125 



that in the antidromic vaso-dilatation, as well as in the redden- 

 ing and inflammatory changes ensuing on local excitation; we are 

 dealing with axon reflexes, perhaps the only remains of the local 

 reflexes of a primitive peripheral subcutaneous nervous system. 

 If croton oil or mustard oil be applied to the skin or to the conjunc- 

 tiva, redness, swelling, and all the signs of a local inflammation are 

 produced. The course of events is not altered by destruction of the 

 central nervous system or by section of the sensory nerve-roots (pos- 

 terior spinal root or trigeminus) on the central side of the ganglion. 

 If, however, they be divided peripherally of the ganglion, and time be 



sup. nerve plex. 



Sens. n. f. 



\ 



skin 



art. 



FIG. 472. 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. 



allowed for complete degeneration of the nerve fibres to their peri- 

 pheral terminations, the application of croton or mustard oil, even to the 

 delicate conjunctiva, is without effect. The same results may be pro- 

 duced if the peripheral terminations of the nerves be paralysed by the 

 subcutaneous injection of local anaesthetics. We must assume that 

 the axons of the peripheral sensory nerves branch, some branches 

 going to the surface, others to the muscle-cells of the cutaneous 

 arterioles, as indicated in the diagram (Fig. 472). 



Graskell has drawn an analogy between the nerves distributed to the 

 blood-vessels and those going to the heart, which is indeed only a 

 specialised part of the general blood-tubes of the body. These nerves, 

 according to their action on the metabolic activity of the tissues supplied, 

 are divided by Graskell into anabolic and catabolic nerves. The anabolic 

 nerves, as indicated by their name, cause a building up or regeneration 

 of the contractile tissue. They therefore act as inhibitory nerves. 



