646 NERVOUS SYSTEM. 



distinguished from the ordinary motor or sensory elements ; but the fact of 

 the degeneration of certain cells, others remaining normal, has led to the dis- 

 tinction by certain writers, of trophic cells, and, of course, these must be 

 connected with the parts by trophic nerves. 



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

 columns of the spinal cord are connected with motion, and that impulses 

 generated in these cells are conveyed to the muscles by the anterior roots of 

 the spinal nerves. It also is a fact, no less definite, that when a muscle or a 

 part of a muscle is for a long time deprived of the motor influence by which 

 it is brought into action, its fibres undergo atrophy, become altered in struct- 

 ure and lose their contractility. Starting with these two propositions, and 

 assuming that certain of the ordinary motor cells of the cord are destroyed, 

 it is easy to predict the phenomena to be expected as a consequence of such 

 a lesion. 



The destruction of certain motor nerve-cells connected with the anterior 

 roots of the spinal nerves would certainly produce degeneration of the nerve- 

 fibres to which they give origin. This occurs when any motor nerves are 

 separated from their cells of origin, and it involves no necessity of assuming 

 the existence of special trophic cells or nerves. 



If a few of the motor cells be affected with disease, and if the degenera- 

 tion be gradual and progressive, there would necessarily be 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 weakening of the muscles, 

 and the phenomena would not be those observed in complete paralysis pro- 

 duced by section of the motor nerves. These are the phenomena observed 

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

 result of the disease ; and these do not of necessity involve the action of any 

 special centres or nerves. 



As regards the muscular atrophy itself, if the nervous stimulus be grad- 

 ually destroyed, the muscular tissue will necessarily undergo progressive de- 

 generation and atrophy. 



With the above considerations, the question of the trophic cells and 

 nerves may be left to the pathologist ; and the existence of centres and 

 nerves specially and directly influencing the nutrition of the muscular sys- 

 tem can be admitted only when it has been demonstrated that there are 

 lesions of particular structures in the nervous system, which produce phe- 

 nomena that can not be explained by the action of ordinary motor and sen- 

 sory nerves and of the vaso-motor system. In thus dismissing the question, 

 however, it is not intended to assume that the existence of trophic centres 

 and nerves is impossible. There are certain peculiar changes in tissue in 

 progressive muscular atrophy, and section of nerves produces degenerations 

 of glandular and other structures that are not muscular. Future observations 

 may show that there are special parts of the nervous system presiding over 

 nutrition ; but at present, such parts have not been accurately described and 

 isolated, either anatomically or physiologically. 



