110 NERVOUS TISSUE. 



observations, of a structureless, somewhat elastic membrane, which 

 does not swell in a gelatinous-like manner in acetic acid, is not 

 dissolved either by boiling or by treatment with dilute alkalies, 

 and cannot, therefore, at all events, consist of pure connective 

 tissue. It dissolves completely in concentrated acetic acid, as 

 well as in solutions of potash and soda after prolonged digestion 

 or boiling, and likewise in concentrated sulphuric acid, but does 

 not dissolve in concentrated nitric acid, which appears to impart 

 a yellow colour to the empty sheaths, although it cannot be dis- 

 tinctly determined by the microscope whether this pale yellow 

 colour proceeds from the sheath itself or from the small quantity 

 of albuminous matter remaining in the partially emptied nerve- 

 fibre. We are thus led to the hypothesis advanced by Mulder* 

 and Kolliker,-)- that the sheath of the nerve-fibre consists of a 

 substance not unlike elastic tissue, from which it, however, differs 

 by its solubility in boiling acetic acid, and by its greater solubility 

 in a solution of potash. It is very analogous to the substance of 

 the sheath of the primitive bundles of muscles, but resembles a true 

 protein-substance much more nearly than does the elastic tissue. 



The axis-cylinder consists, according to all the above-mentioned 

 reactions, of a protein-substance which presents many resem- 

 blances to the substance of the muscular fibrils (syntonin), 

 although it is certainly not identical with it. The substratum of 

 the axis-cylinder shows itself to be a protein- substance by its 

 behaviour towards acetic acid and very dilute hydrochloric acid, 

 towards dilute and concentrated alkaline solutions, towards concen- 

 trated nitric acid and potash, as well as towards concentrated 

 sulphuric acid. This substance differs from ordinary blood-fibrin 

 by the difficulty with which it dissolves in acetic acid, and by its 

 perfect insolubility in carbonate of potash, as well as in a solution 

 of nitre after a prolonged digestion at a temperature of 30 ; and it 

 is distinguished from muscle-fibrin (syntonin) by its insolubility in 

 dilute hydrochloric acid, and by the difficulty with which it dis- 

 solves in acetic acid. It is scarcely possible to confound it with 

 the substratum of any other elementary tissue. The substratum 

 of elastic tissue is perfectly insoluble in dilute alkalies and in acetic 

 acid. Moreover, the substance of the axis-cylinder cannot be 

 composed of gelatigenous connective tissue ; for, independently of 

 the above-described behaviour towards acids and alkalies, it under- 

 goes no change whatever when boiled with water. Least of all 



* Vers. einer physiol. Chemie, S. f>55 [or English Translation, p. 602]. 

 t Mikrosk. Anat. Bd. 2, S. 397. 



