STRUCTURAL ALTERATIONS IN NERVE CELLS 217 
(3) That the diminution in number is most marked in the Vllth segment. 
(4) That the posterior lateral group is the one in which the phenomena of chromatolysis 
remain longest. 
(5) That the main factor iti the diminution in the number of cells on the side of the 
lesion is atrophy of the posterior lateral group of cells. 
The observations thus quoted afford further evidence of the necessity of continuity of 
the afferent impulses if the anatomical integritv of tiie motor cells of the cord is to be maintained. 
This doctrine of the trophic impulse which one neuron exerts on another was enunciated 
by Marinesco* in 1892, in his study of the changes which takes place in old amputations, and 
again in 1895 in his ' Tlieories des Neurones,'! and it has been accepted by Van GEHUCHTEN,t 
who says, ' Les cellules nerveuses du nevraxe exercent I'une sur I'autre une action trophique 
dont la suspension complete cntrainc la chromatolysis et la disparition des cellules correspondantes.' 
This theory receives support from the well-known fact that the cells of Clarke's column 
are often found atrophied in cases of Tabes Dorsalis. Again, both Marinesco and Van 
Gehuchten agree that after section of the pneumogastric nerve the cells in the dorsal nucleus of 
the medulla show chromatolysis. 
The theory of the trophic influence on one another of related neurons may be regarded 
as the explanation of this fact, at least until the view of the motor nature of these cells put 
forward by Van Gehuchten and Bruce is better established. 
I regard the preponderating degree in which the posterior lateral group of cells in the cord 
is affected as further evidence in support of tins view. 
This is the group of cells which is known to be chiefly affected in the case of old 
amputations, and recent experiments of other writers can be instanced showing the same fact. 
Thus Van Gehuchten^ divided the great sciatic nerve, and on subsequent examination of the 
cord found the cells of the posterior lateral group alone affected. They were in the pycno- 
morphic state, which he regards as representing a simple manner of cell reaction. The same 
author and De Buck.|| quote a case in which 21 days after amputation at the knee-joint the cells 
of this group alone were found to be in a state of chromatolysis. SanoH also gives corroborative 
statements. 
IV. THE EFFECT OF TRANSECTION OF THE CORD ON THE CELLS 
IN THE GREY MATTER BELOW THE LEVEL OF THE LESION 
A considerable number of clinical observations have been made sliowing that after lesions 
of the brain rapid atrophy, usually localized to particular groups of muscles, may take place. 
Charcot, whose explanation has also been adopted by Goldscheider, regarded this atrophy as 
due to a lesion of the cells in the anterior horn consequent on the affection of the pyramid tracts, 
* Marinesco. ' Neurol. Centralb.' 1892. 
Marinesco. La ' Presse Meilicale.' 1895, p. 545. 
X Van Gehuchten. ' Bull, de I'Acad. Royale He M^decine 
He Belgique.' 1897, p. 821. 
§ Van Gehuchten. ' Bull, de I'Acad. Roy. de Medecine 
de Belgique,' 1898, p. 222. 
II Van Gehuchten and De Buck. ' Annales et Bull, de 
la Soc. ile Med. de Gan.l,' 1897, p. 268. 
^ Sano. 'Journal de Neurologie,' Nos. 13 and 14. 182;-. 
2 C 
