742 NERVOUS SYSTEM. 



spinal centres are not absolutely necessary to development in utero. Some of the cases 

 reported presented spasmodic movements of certain muscles. 



"While it is certain that a foetus may become developed in utero, when there is reason 

 to suppose that the cerebro-spinal influence is wanting and the chief nervous operations 

 are effected through the ganglionic system, direct experiments upon the sympathetic in 

 animals do not positively show any influence upon nutrition, except as this system of 

 nerves affects the supply of blood to the parts. When we divide a sympathetic nerve, 

 there is an apparent exaggeration of the nutritive processes in particular parts, and there 

 may be inflammatory phenomena, but atrophy of muscles is not observed. Indeed, we 

 only have atrophy of muscles following division of cerebro-spinal nerves, or, as recently- 

 observed cases of disease have shown, after disorganization of cells belonging to what we 

 recognize as motor centres. As regards the latter condition, there can be no doubt of 

 the fact that progressive muscular atrophy is attended with disorganization of certain of 

 the motor cells of the spinal cord. 



Without fully discussing this subject, which belongs to pathology, the facts may be 

 briefly stated as follows : We may have progressive atrophy of certain muscles, which 

 may be uncomplicated with paralysis except in so far as there is weakness of these mus- 

 cles, due to partial and progressive destruction of their contractile elements. The only 

 pathological condition in these cases, aside from the changes in the muscular tissue, is 

 destruction of certain cells in the antero-lateral portions of the cord, with more or less 

 atrophy of the corresponding anterior roots of the nerves. No one has pretended to 

 have demonstrated cells in the cord, presenting anatomical peculiarities by which they 

 may be distinguished from the ordinary motor or sensory elements, but the fact of the 

 degeneration of certain cells, others remaining normal, and this fact alone, has led to the 

 distinction, by certain writers, of trophic cells ; and, of course, these must be connected 

 with the muscles by trophic nerves. 



We shall now study the phenomena of progressive muscular atrophy from a physio- 

 logical point of view, and see if they aiford any positive evidence of the existence of 

 special cells and nerves presiding over the nutrition of the muscular system, or whether 

 the phenomena observed cannot be explained by the partial degeneration of the ordinary 

 motor cells and nerves. 



There can be no doubt of the fact that the cells of the antero-lateral columns of the 

 spinal cord preside over motion, and that the stimulus generated in these cells is con- 

 veyed to the muscles by the anterior roots of the spinal nerves. It is a fact, no less 

 definite, that, when a muscle or a part of a muscle is deprived of the motor stimulus by 

 which it is brought into action, its fibres atrophy, become altered in structure, and lose 

 their contractility. Starting with these two well-defined physiological propositions, and 

 assuming that a few of the ordinary motor cells of the cord are destroyed we will not 

 call them trophic cells what are the phenomena to be expected as a consequence of 

 such a lesion ? Reasoning from what we know of the physiology of the nervous system, 

 we should expect to find the following conditions : 



The destruction of certain motor nerve-cells would certainly produce degeneration of 

 the fibres to which they give origin. This has been observed; for, in this condition, the 

 anterior roots arising from the diseased portions of the cord are atrophied. This occurs 

 when any motor nerves are separated from their cells of origin, and it involves no neces- 

 sity of assuming the existence of special trophic cells or nerves. 



If a few of the motor cells be affected with disease, and if the degeneration be gradual 

 and progressive, we should expect progressive and partial paralysis of the muscles to 

 which their nerves are distributed. This paralysis, confined to a limited number of 

 fibres of particular muscles or sets of muscles, would give the idea of progressive weak- 

 ening of the muscles, and the phenomena would not be those observed in complete 

 paralysis produced by section of the motor nerves. These are precisely the phenomena 

 observed in progressive muscular atrophy, preceding the paralysis which is the final 



