THE CAUSATION OF DISEASE. 9 1 



and, finally, these cells possess a well-marked structure, by 

 which I mean one that we can detect by examination, for we 

 have seen all cells possess a highly complex structure. 



The degeneration of the anterior ganglionic cells in progres- 

 sive muscular atrophy is undoubtedly, to a large extent, an 

 inverted evolution. In order to be sure of this, it is necessary 

 to study the evolution of these cells. This has been done by 

 observing their appearance at different stages of development. 

 If we examine the cervical region of the cord during early 

 infancy, the anterior ganglionic cells will be found to be not 

 only simple in structure, but also comparatively few in number, 

 this immaturity corresponding with the volitional incapacity of 

 the young infant, who is, as yet, utterly helpless. Gradually, 

 however, they increase in number and complexity : at first 

 round and small, they enlarge, and, at the same time, push out 

 a number of branching processes. Thus are formed complex 

 motor centres, and it is upon the grouping of these cells into 

 centres that the proper grouping of muscles in ordinary 

 voluntary acts, in very large measure, depends ; for, be it 

 remembered, what is apparently a very simple muscular act, 

 is found, when dissected into its component parts, to be a 

 very complex process. It may be remarked, by the way, that 

 the growth of voluntary power is not a mere matter of educa- 

 tion, as taught by Bain, for, as just observed, the structural 

 basis whereby voluntary action becomes possible, is, at birth, not 

 yet developed in the nerve ganglia. Moreover, the voluntary 

 cortical centres are at this time equally backward in develop- 

 ment; so that, even if the new-born infant possessed fully 

 developed mental powers, voluntary action would be quite 

 impossible.* 



In considering the structure of the anterior ganglionic cell, 

 we have to remember that one of its processes is prolonged 

 into the axis cylinder process of a motor nerve fibre, this 

 axis cylinder process, as it has been termed, becoming, in 

 due course, coated with medullary sheath and neurilemma ; 

 and the entire nerve fibre thus constituted terminates in the 



* Bastian. I do not intend to imply by the above that voluntary power is not 

 gained by education, but rather that the immaturity of the motor mechanism 

 at birth must be taken into account when studying the growth of the will. 



