ITS CHEMICAL CONSTITUTION. Ill 



could we have expected that any one should regard the axis- 

 cylinder as composed of fat, or at all events, of a very fatty sub- 

 stance, as Mulder and Bonders have actually done. The con- 

 stantly recurring cylindrical form which is observed on the 

 application of the very different reagents which have been men- 

 tioned, the great coherence, the elasticity and sharp outline of the 

 axis-cylinder, its complete insolubility in boiling alcohol and ether, 

 its continuous visibility on the application of reagents which expel 

 and dissolve the fat from the nerve-tubes, and, lastly, the entire 

 absence of experimental evidence that a fat can under any circum- 

 stances be converted into a consistent and resistent filament, 

 incline us to believe that Mulder's assertion must be ascribed 

 either to a simple error of memory or to a lapsus calami; for, 

 although we may not be able to prove definitively that the axis- 

 cylinder is wholly free from fat, the above reactions appear to 

 show beyond a doubt that it consists essentially of a protein-like 

 body, and that the fat which is so abundant in the nerves is prin- 

 cipally, and in all probability, entirely accumulated in the nerve- 

 pulp. Kolliker has been led to advocate this view from his 

 investigations regarding the axis-cylinder. 



The medulla or nerve-pulp appears, as we have already seen, to 

 be perfectly homogeneous in recent preparations of the nerves, and 

 moreover so perfectly transparent, that we can scarcely conceive 

 it to be anything more than a viscid emulsive fluid, although the 

 above indicated micro-chemical reactions, and the behaviour of the 

 nerve-pulp in water, and on exposure to cold, show, that in addi- 

 tion to an abundant supply of fat, it also incloses a protein -sub- 

 stance, permeated by aqueous moisture. I can hardly compare 

 this protein-substance to coagulated albumen, as some other 

 observers have done, for albumen in a state of coagulation would 

 easily admit of being distinguished under the microscope from fat, 

 by the molecular form which it presents in this condition. It may 

 very probably be regarded as corresponding with soluble albumen or 

 casein, for when chemists engaged in analyses of the cerebral sub- 

 stance speak of coagulated albumen, they do not refer to the albu- 

 men of the true nerve-pulp, but to the fibrin-like matter of the 

 axis-cylinder. The albuminous substance of the nerve-pulp is, how- 

 ever, entirely different from the matter forming the axis -cylinders. 

 This substance is soluble in, or rather, it may be extracted from 

 the nerve-pulp by a dilute solution of soda, and by acetic acid when 

 not too much diluted ; so that after repeated treatment with boiling 

 alcohol or ether, the nerves appear to be perfectly empty, with the 



