204 On Trophic Nerves. [April, 



vis a f route of the tissues surrounding the capillaries and acting 

 then upon the circulation. The present writer is only half inclined 

 to believe that this is a vera causa in animal hydraulics or " haeniau- 

 lics ; " and that at all events we are not absolutely necessitated to 

 accept it as such, though the absence of any other plausible hypo- 

 thesis may be seen from the following record of an observation 

 made and published by him before he was acquainted with either 

 of the two memoirs just referred to. This record will be found in 

 * Medicine in Modern Times,' at p. 69, and to the following effect : — 



" The following short history seems to me to be a good instance 

 of the action, or rather of the want of action, of the peripheral nerve- 

 system upon the arterioles. A man, who came some years ago under 

 my own care had had a bullet pass through his arm just above the 

 elbow, so as to sever the miisculo-spiral nerve. The scars of exit 

 and entrance were in the lower third of the arm. Under ordinary 

 circumstances the soft parts of the lower arm maintained their 

 natural consistence ; but their power of resisting changes of tempe- 

 rature was greatly impaired, as well of course as the sensibility of 

 the parts supplied by the injured nerve. I recollect seeing the 

 swollen state of the inner side of the hand one cold, raw morning, 

 when the man was on sentry duty, and had his hand chilled down 

 by the musket he had to carry. Xow, I apprehend that this tur- 

 gescence is to be explained by saying that the local or peripheral 

 nerve-system of the affected parts was competent under ordinary 

 circumstances to regulate the calibre of the arteries ; but that its 

 activity was liable to be depressed, as under the circumstances 

 related, into actual abeyance in the absence of any possibility of 

 any assistance being supplied to it from the cerebro-spinal nerve- 

 axis. Thus, under the depressing effect of cold, which seems to 

 work here much as it does in checking the regeneration of artificially 

 amputated parts in snails and in salamanders,* the peripherally- 

 placed ganglionic system was put into abeyance, and turgescence 

 of the vessels it ordinarily supplied witn ' tone ' ensued." 



It may be said that we do actually know and can see that a 

 nerve when severed from its central connections undergoes fatty 

 degeneration ; that it is reasonable to suppose that its mal-nutiition 

 may entail a consentaneous mal-nutrition in the parts which it sup- 

 plies ; and that this secondary mal-nutrition may account for the 

 reduction thus witnessed of the tissues of warm-blooded animals to the 

 level of those of the cold-blooded classes. But to this we reply that 

 atrophy of the nerve-trunk is one thing, and a thing very demon- 

 strable ; whilst atrophy of the terminal nucleate plexus, in which so 

 many nerves have of late been shown to terminate, is another thing, 

 and as yet an undemonstrated one. Indeed the physiological existence 



* ' Miiller's Physiology,' by Baly, 2nd edition, i.. p. 444 ; Bonnet, ' CEuvres.' 

 torn. v.. i.. pp. 328. 329. 



