CHAPTEK XVIII 



TKOPHIC NERVES 



NERVES exercise a trophic or nutritive influence over the tissues and 

 organs they supply ; for when a nerve going to an organ is cut, the 

 wasting or degenerative process continues beyond the nerve; the 

 muscles it supplies waste also, and waste much more rapidly than 

 can be explained by simple disuse. The same is seen in the testicle 

 after section of the spermatic cord ; and in the disease of joints called 

 Charcot's disease, the trophic changes are to be explained by disease 

 of the nerves supplying them. After the division of the fifth cranial 

 nerve there is loss of sensation in the corresponding side of the 

 face: the cornea in two or three days begins to get opaque, and 

 this is followed by a slow inflammatory process which may lead to a 

 destruction not only of the cornea, but of the whole eyeball. The 

 same is seen in man ; when the fifth nerve is diseased or pressed 

 upon by a tumour beyond the Gasserian ganglion, the result is loss 

 of sensation in the face and conjunctiva, an eruption (herpes) appears 

 on the face, and ulceration of the cornea leading in time to disinteg- 

 ration of the eyeball may occur too. In disease such as haemorrhage 

 in the spinal ganglia there is a similar herpetic eruption on the skin 

 (shingles). 



In the case of the fifth nerve the evidence that there are special 

 nerve-fibres to which these trophic changes are due, is an experiment 

 by Meissner and Buttner, who found that division of the most 

 internal fibres is most potent in producing them. 



Those, however, who do not believe in special trophic nerves, 

 attribute the changes in the eyeball to its loss of sensation. Dust, 

 etc., is not felt by the cornea, and is therefore allowed to accumulate 

 and set up inflammation. This is supported by the fact that if the 

 eyeball is protected by sewing the eyelids together the trophic results 

 do not ensue. On the other hand, in paralysis of the seventh nerve, 

 the eyeball is much more exposed, and yet no trophic disorders 

 follow. 



Others have attributed the change to increased vascularity due 

 to disordered vaso-motor changes; against this is the fact that in 



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