22 NERVOUS SYSTEM. 



ner as the medullary substance, and it cannot "be demon- 

 strated afterward, on account of the opacity of the coagulated 

 matter. If a fresh nerve, however, be treated with strong 

 acetic acid, the divided ends of the fibres will retract, leaving 

 the axis-cylinder, which 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 vari- 

 cose at intervals, somewhat granular, and sometimes very 

 finely striated in a longitudinal direction. This band is 

 elastic, but not very resisting. Its granules are excessively 

 pale. "What serves to distinguish it from all other portions 

 of the nerve-fibre is its insolubility in most of the reagents 

 employed in anatomical investigation. It is slightly swollen 

 by acetic acid, but is dissolved after prolonged boiling. If 

 a solution of carmine be added to the nervous tissue, the 

 axis-cylinder only is colored. It has been remarked that 

 the nerve-fibres treated with nitrate of silver present in the 

 axis- cylinder well-marked transverse striations. This was 

 observed by Frommann, 1 and has since been confirmed by 

 Grandry. 3 The latter observer is disposed to 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 developed by the nitrate of silver. This, however, is 

 a point of purely anatomical interest. The presence of regu- 

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

 tion of a solution of nitrate of silver and the action of light 

 cannot be doubted ; but it has not yet been determined be- 

 yond question whether these markings be entirely artificial, 

 or whether the axis-cylinder be really composed of two kinds 

 of substance. 



A still more important question with regard to the inti- 



1 FROMMANN, Ueber die Fiirbung-der Binde- und Nervensubstanz des Rucken- 

 markes durch Argentum nitricum und uber die Struktur der Nervenzellen. 

 Archiv fur pathologische Anatomic und Physiologic, etc.', Berlin, 1864, Bd. xxxi., 

 S. 129, et seq. Zur Silberfdrbung der Axencylinder, ibid., S. 151, et seq 



2 GRANDRY, JDe la structure intime du cylindre de Vaxe et des cellules nerveuses. 

 Journal de F anatomic, Paris, 1889, tome vi., p. 289, et seq. 



