876 THE SPINAL CORD. 



and its regeneration prevented. Accompanying this histological change, and in 

 a sense heralding it, are the well-known alterations in the electrical reaction of 

 the muscle, which characterise the "reaction of degeneration." The muscle 

 comes to respond to electrical stimuli in a manner apparently qualitatively 

 different from normal. The excitability of the muscle to induced currents is 

 abolished, that to the constant current is exaggerated. In regard to the response 

 to the latter, the normal order of appearance of contraction, as the strength of the 

 current is gradually increased from subliminal, begins with the kathode to the 

 muscle and at the making of the circuit. To obtain a contraction when the anode 

 is applied to the muscle and the current is made, requires a stronger current. In 

 a well-marked reaction of degeneration, the anodal contraction, at make, appears 

 with a weaker stimulating current than that required for the kathodal contraction 

 at make. The contraction is greatly prolonged. Galvanotonus is easily produced. 



Disease of sensory as well as of motor nerves is accompanied by 

 change in the condition of nutrition of peripheral tissues. Alterations, 

 both of atrophic and inflammatory kind, occur in the skin in relation to 

 primary changes in nerve trunks. Of the latter alterations the course 

 of herpes zoster is one example. The primary lesion seems an inflam- 

 matory condition of the spinal ganglion ; l on this ensues an eruption 

 more or less occupying the field of skin for which the ganglion cells 

 provide sensory channels. There is severe pain referred to the area of 

 skin. Head's recent researches 2 have placed beyond doubt the connec- 

 tion between this cutaneous eruption and focal inflammation of corre- 

 sponding spinal ganglia. Occasionally a similar herpes ensues on irrita- 

 tion of the ganglia in spinal caries. 



When the afferent spinal roots belonging to a limb are severed — 

 proximal to the ganglia — there is distinct wasting in much of the 

 musculature of the limb ; and, especially in the lower limb, ulceration is 

 prone to occur on the outside of the ankle-joints. In man, where injury 

 of the spinal cord upsets the condition of the skeletal musculature more 

 than in animals, and where, therefore, the disturbance to the skin is prob- 

 ably also proportionately greater, there is especial tendency for ulceration 

 (bed-sores) of the skin and tissues to occur ; but these are met with as 

 the result of similar lesions in laboratory animals. 



When all these cases are examined, so far as by present methods they 

 can be, they seem to yield evidence that every nerve and nerve centre 

 that can influence the proper and specific activity of a tissue — and 

 that is the sole function of nerves — possesses, in so far, a trophic 

 influence on that tissue. If by trophic nerve be understood^ no more 

 than this, all nerves are trophic nerves. That, on the other hand, any 

 nerve directly modifies the nutrition of a tissue independently of 

 inducing vascular changes in it, or influencing those particular meta- 

 morphoses of material for which the tissue is the machine specifically 

 adapted, there is no proof. The function and the nutrition of these 

 physiological machines form an inseparable unity. Such a doctrine is 

 a just corollary to the cell theory. Under the notion of normal nutri- 

 tion is understood maintenance of a certain average form and certain 

 average chemical composition. When the maintenance of the nutrition of 

 one cell is directly and greatly dependent on the maintenance of another, 

 the inference amounts to certainty that the latter governs the function 

 of the former. This consideration shows clearly how, far more than any 



1 v. Biirensprung, 1861. 



2 Allbutt's "System of Medicine," London, 1899, vol. viii. p. 635. 



