ITS MICRO-CHEMICAL RELATIONS. 101 



gives rise to very few visible alterations in the microscopical 

 characters of the nervous substance. Hot, or more correctly 

 speaking, boiling alcohol behaves differently ; for, as we might 

 assume a priori, it Coagulates the coagulable parts of the nerves, 

 and dissolves the fat and the salts of the fatty acids. When the 

 nerve-fibres are boiled in alcohol the nerve-sheath exhibits a 

 sharper outline, appearing at different points as a special mem- 

 brane, distinct from the granular contents. The contents have the 

 appearance of less dark and less well defined granules, and are 

 generally translucent and somewhat faintly defined. The axis- 

 cylinder often stands out very well in some fibres, although a 

 careful preparation and some minutes' boiling are necessary to 

 exhibit this clearly. The nerve-cells are but slightly altered by 

 boiling with alcohol, the change they undergo being for the most 

 part limited to an appearance of slighter granulation. The alcohol 

 in which the nervous matter has been boiled exhibits on cooling 

 white flakes, which appear, when seen under the microscope, to be 

 neither crystalline nor of the nodular form common to the fat of 

 the nerves, but to consist of a confused mass of fine molecular 

 granules. (F. P. 15, F. 6.) 



Cold and hot ether behave towards the nervous elements in 

 much the same manner as alcohol, and like the latter, render 

 large pieces of nervous substance somewhat harder. When 

 examined under the microscope the double contour of the cere- 

 bro-spinal nerves is found to disappear under the prolonged 

 action of ether, whilst the sheath appears more distinct at certain 

 points, and studded, as it were, with granules in many parts. The 

 granular contents are rendered considerably paler, whilst here arid 

 there the axis-cylinder is seen paler, and like a twisted thread. 

 The action of ether on the nerve-cells is as slight as that of alcohol. 

 The ether in which the nerve-fibres have been digested deposites 

 on evaporation white granules, which appear, when seen under the 

 microscope, to consist of crystals of margaric acid and nodular 

 masses of brain fat. 



Dilute acetic acid produces no marked alteration in the mor- 

 phological character of the nerve-tubes, but when this acid is used 

 in a highly concentrated state, the nerve-fibres after its prolonged 

 action acquire a sharply defined outline. Although the inner 

 contour becomes somewhat distorted after boiling, the sheath 

 becomes distinctly visible at certain points on the cut surfaces of 

 the nerve-fibres ; between the inner contours there remains a 

 coiled, often pale reddish stripe ; thin, very pale threads frequently 



