Manchestei' Memoirs, Vol. xlii. (1898), No. \%. 1 1 



may live for a brief period on its accumulated vital capital, 

 but when this is expended perishes; it cannot live of itself, 

 it cannot grow, it cannot reproduce itself The fragment 

 containing the nucleus, however, can live of itself, can 

 grow, can reproduce itself The nerve cell obeys the same 

 law; the nucleus governs the nutrition of the whole unit, 

 not only of the ordinary dendrites and of the cell body 

 immediately surrounding itself, but of the whole axon, 

 however long that be. The efferent nerve fibre is depen- 

 dent for its nutrition on the nucleus of the cell in the 

 spinal cord or brain, of which it is a prolonged axon. The 

 afferent nerve fibre is dependent for its nutrition on the 

 nucleus of the cell in the posterior spinal ganglion (or 

 analogous structure), of which it is, as we have seen, either 

 a prolonged and specialized dendrite or a portion of an 

 axon. If either fibre be cut off from its nucleus, it under- 

 goes degenerative changes, it dies, never to become alive 

 again, though it may be, and that even exactly, replaced 

 by a growth of the stump left behind still in connection 

 with the nucleus. 



This nutrition of the long-extended nerve fibre, be it 

 called an axon or dendrite, is in many respects a complex 

 and peculiar business. The fibre along its whole length is 

 supplied with blood vessels and bathed in lymph; from 

 this lymph it takes up material, far away from the nucleus, 

 and by this lymph it is directly nourished ; for if this local 

 nutriment be interfered with, it, the fibre suffers, however 

 intact may remain its ties with its nucleus. Yet it cannot 

 avail itself of this nourishment unless those ties be intact. 

 Something is continually going on between the nucleus 

 and far-distant parts of the axon which determines the 

 absorption and utilisation of the material lying to hand 

 around those distant parts. 



Further, in all living units we are able, by careful 

 observation, to catch sight of visible tokens of the work of 



