112 NERVOUS TISSUE. 



exception of the axis-cylinder. When nerve-fibres have been 

 treated with alcohol or ether, after having been exposed to the 

 action of concentrated nitric acid, or conversely when they have 

 first been treated with nitric acid, and subsequently with a fat-sol- 

 vent, they still exhibit finely granular yellow-coloured contents, 

 which can be nothing else than this protein-substance, which is 

 now in a coagulated state. I have frequently been at great pains to 

 ascertain the presence of a protein -substance coagulable by boiling 

 or by acetic acid in cerebral matter which had been extracted with 

 water ; but from various causes, amongst which may be mentioned 

 the emulsive form which the fluid constantly presented, the blood- 

 serum which it always contained, and the power exerted by acetic 

 acid in decomposing the fatty matters, I was prevented from obtain- 

 ing any undoubted result. Although it is very difficult to obtain 

 direct proof from microscopical observations, or rather to form a 

 judgment from them, the descriptions of the alterations experienced 

 by the nerve-pulp on the addition of different reagents (in becom- 

 ing coarsely or finely granular or crystalline) seem to indicate that 

 the nerve-pulp contains a soluble protein-substance in the 

 closest admixture with a fat dissolved by easily decomposable 

 soaps, and that the visibility of the pulp is owing less to the coagu- 

 lation of this albuminous body than to the separation of the fat 

 from the decomposing soaps and the albuminous substance. It 

 might, indeed, be assumed from the alteration which is gradually 

 perceptible in the pulp of fresh nerves, 011 exposing them to the 

 action of the air, water, or cold, that a substance similar to the 

 fibrin of the blood was in solution in the fresh nerve, and subse- 

 quently coagulated like blood-fibrin ; but repeated microscopico- 

 mechanical investigations of the nerve-fibre do not especially favour 

 this hypothesis, for the substance which is separated has always 

 more or less the character of fat, but not that of fibres (like coagu- 

 lating blood-fibrin), or that of the finest molecular granules (like 

 other protein-bodies in coagulating). For even if we assume such 

 a spontaneous coagulation of the albuminous substance of the 

 nerve-pulp, the undoubted separation of the fat would still remain 

 unexplained, and we should be compelled to have recourse to the 

 preceding conjecture, regarding the separation of the fat from the 

 solution of the salts of the fatty acids. It seems to us, however, 

 that Henle's* view, that the nerve-pulp is not an emulsion, but an 

 actual solution or mixture, leaves no doubt in relation to this 

 question. 



* Allg. Anat. S. 624. 



