NON-MEDULLATED NERVE-FIBRES 



459 



stance ; and it can not easily be demonstrated afterward, on account of 

 the opacity of the coagulated matter. If a fresh nerve, however, is 

 treated with strong acetic acid, the divided ends of the fibres retract, 

 leaving the axis-cylinder, which latter is but slightly affected by reagents. 

 It then presents itself in the form of a pale, slightly-flattened band, with 

 outlines tolerably regular, though slightly varicose at intervals. It is 

 somewhat granular and finely striated in a longitudinal direction. This 

 band is elastic but not very resisting. What serves to distinguish it 

 from other portions of the nerve-fibre is its insolubility in most of the 

 reagents employed in anatomical investigations. It is slightly swollen 

 by acetic acid but is dissolved after prolonged boiling. If nerve-tissue 

 is treated with a solution of carmin, the axis-cylinder only is colored. 

 It also stains with gold chloride. It has been observed that the nerve- 

 fibres treated with silver nitrate present in the axis- 

 cylinder well-marked transverse striations (Fromann) ; 

 and some anatomists regard both the nerve-cells and 

 the axes of the fibres as composed of two substances, 

 the limits of which are marked by the regular striae 

 thus developed. This, however, is a point of purely 

 anatomical interest. The presence of regular and 

 well-marked striae in the axis-cylinder after the addi- 

 tion of a solution of silver nitrate and the action of 

 light can not be doubted; but it has not yet been 

 determined whether these markings are artificial or a> shows compon ent 

 whether the axis-cylinder is really composed of two fibrin* ; *. shows vari - 



cose nerve-fibrillae near 

 kinds Of Substance. their termination. 



For some time it has been known that the axis- 



cylinders in the organs of special sense, in the final distribution of 

 sensory nerves and in some other situations, break up into fibrillae. A 

 fibrillated appearance, indeed, is often observed in nerves in their 

 course, and it is now the common opinion that the axis-cylinders are 

 composed of fibrillae held closely together by connective substance. 

 This fibrillated structure of the nerves is quite prominent in some of the 

 lower orders of animals. 



Non-medullated Nerve-fibres. These fibres, which are largely dis- 

 tributed in the nervous system, appear to be simple prolongations, with- 

 out alteration, of the axis-cylinders of the medullated fibres. They are 

 found chiefly in the peripheral terminations of the nerves and in the 

 filaments of origin of the fibres from the nerve-cells. Some anatomists 

 think that they have a delicate investing membrane, but this has not 

 been satisfactorily demonstrated. 



Gelatinous Nerve-fibres (Fibres of Remak). There has been some 



