ITS MICRO-CHEMICAL RELATIONS. 107 



we can obtain even a moderately good preparation, in consequence 

 of the extreme difficulty of separating the fibres. When viewed 

 under the microscope the isolated nerve-fibres appear coiled in an 

 intestine-like manner and somewhat distended, the sheath cannot 

 readily be distinguished, and the pulp is converted into a somewhat 

 coarsely granular matter, showing no distinct central fibres ; it is 

 only at particular points that a portion of the axis-cylinder may be 

 seen projecting from the extremity of a fibre like the wick from 

 the end of a candle. 



When immersed in a concentrated solution of carbonate of 

 potash, the nerve-tubes swell somewhat up, and seem partially 

 twisted, the nerve-sheath being unequally extended, so that the 

 tube resembles the colon in form. The individual dilatations are 

 not sharply separated from each other, but on the whole the con- 

 tents are rather clear and translucent than granular ; the axis- 

 cylinder and sheath cannot be recognised. Some light roundish 

 filaments may be seen at the extremities of individual nerve-fibres 

 which bear an extraordinary resemblance to axis-cylinders, although 

 it is not very certain that they may not be due to the connective 

 tissue, which frequently gives rise to precisely similar filaments. 

 In our description of the above experiments we have therefore 

 only designated these filaments as axis-cylinders in those cases in 

 which their form and position showed they could be nothing else. 

 Objective certainty was unattainable in regard to these filaments, 

 although it seems in the highest degree probable that the axis- 

 cylinder remains uninjured in carbonate of potash. 



Virchow* first noticed that the substance of the nerves becomes 

 hardened in solutions of carbonate of potash ; the fact, observed 

 by my friend Ed. Weber, is especially worthy of notice, that the 

 course of the fibres may be traced in an extremely beautiful 

 manner in the brain and spinal cord, when they have been pre- 

 viously treated with a solution of this salt. 



The nerve-cells are also but slightly altered in form in solutions 

 of carbonate of potash. 



If prepared nerves are suffered to be immersed for any length 

 of time in a dilute solution of soda, the separate fibres appear to 

 become more faintly granulated, somewhat contracted in their 

 diameter, and no axis-cylinder can be detected ; the double con- 

 tours of the cerebro-spinal fibres are also no longer visible. But 

 when a dilute solution of soda is added to a fresh preparation whilst 

 under the microscope, the sheath contracts, as was observed by 

 * Zeitsch. f. rat. Med. Bd. 4, S. 2J6. 



