380 Dr. Waller [May 31, 



the fibres had been reconstituted and re-united to their central organ. 

 This real loss of function was to be distinguished from the apparent 

 loss in which paralysis consists ; for a motor nerve that was paralyzed 

 by section, might still be stimulated to discharge its functions by gal- 

 vanism for some days after it had been separated from its centre. No 

 change, however, took place in the fibres of the upper portion of a 

 divided nerve. The slowness with which the regenerated nerve ac- 

 quired its normal functions, was probably due to the small size and 

 imperfect conducting power of the new fibres in the cicatrix. 



Some of the results which had followed from a knowledge of this 

 process were then pointed out. In the first place, we learned from it 

 how essential the medullary substance of the nerve-fibres is to their 

 vitality, since its destruction and removal is followed by a complete 

 abolition of their functions. Was it, it was suggested, that it bore to 

 the less destructible axial filament and investing membrane a relation 

 analogous to that which the exciting fluid in a voltaic cell does to the 

 metallic poles with which it is in contact ? In either case, the removal 

 of the white substance, or the exciting fluid, caused a loss of power, 

 which was restored by their renewal. The nutritive energy of the 

 white substance, that is, the facility with which it underwent nutritive 

 changes, was also dwelt upon, as indicating that it was a source of 

 power, just as the chemical activity of the fluid in the voltaic cell 

 regulated its potential energy. The readiness which the fluid element, 

 in a voltaic cell, exhibits to undergo chemical change, and to enter 

 into new combinations is, to a great extent, the gauge of the voltaic 

 power which the cell of which it is a constituent is capable of developing. 

 So the readiness with which the medullary constituent of the nerve- 

 fibre undergoes decomposition, when compared with the more stable 

 axis cylinder and investing membrane, which indicate a corresponding 

 activity of nutrition, may be assumed to indicate that it is in some way 

 a reservoir of power for the nerve-fibre, or, at least, that the decom- 

 position which its nutrition involves is a condition of the development 

 of nerve force in the fibre. 



Another result was, the facility with which an application of this 

 process of disorganization had enabled us to trace the distribution of 

 various important nerves. Thus, Dr. Waller had been enabled by it 

 to separate the fibres of the spinal accessory nerve from those of the 

 vagus, and to trace each of them to their distribution in the lungs, 

 heart, and stomach. It had also enabled him to determine the direc- 

 tion of the fibres of the sympathetic nerve in the neck. In fact, it 

 provided physiologists with a means of tracing the course of nerves 

 analogous to that which they had long possessed for tracing vessels, by 

 injecting them with coloured fluids. He had traced in this way the 

 minute distribution of the nerves in the tongue. Thus, we were pro- 

 vided with a means of research, the want of which an old anatomist 

 (Rusych) had expressed, when he said that " he would have nothing 

 further to wish for than to inject nerves, as he had succeeded in 

 injecting blood-vessels." 



