352 SPECIAL HISTOLOGY. 



peripheral thick fibres) and evidently swollen ; they frequently, also, 

 appear convoluted, or even spirally rolled, which is owing, simply to the 

 shortening of the whole nerve caused by the acetic acid. The nerve- 

 pulp itself is rendered grumous by the same reagent ; the grumous 

 particles are sometimes granules, sometimes very short rods, like fat- 

 crystals, which latter may be very often seen on the nerve-fibres, forming 

 stellate, acicular groups (margaric acid) ; alcohol and ether also render 

 the axis-cylinder very distinct, both, when recent nerves are treated 

 with those reagents in the cold, in which case their action must be rather 

 more prolonged, and when they are boiled in them. I can particularly 

 recommend the boiling in absolute alcohol, by which means excellent 

 preparations of the axis-fibres may be made, and in the shortest time. 

 Under this treatment the nerves become firmer, but still admit of being 

 readily torn into fibres, and always exhibit very numerous isolated central 

 fibres of considerable length, which, contrasted with those brought into 

 view by means of acetic acid, are, as it were, contracted (at most 0-002 of 

 a line wide), yellowish, firmer, and often convoluted or twisted. Ether 

 acts in the same manner. By both reagents the medullary sheaths are 

 rendered paler and grumous, the grumous particles frequently appearing, 

 as it were, to be united into a delicate network. When nerve-fibres are 

 boiled, first in ether and afterwards in alcohol, they become quite pale, 

 but the sheath and axis-cylinder perfectly distinct, the latter presenting 

 precisely the same appearance as after treatment with alcohol alone. 

 Consequently, it would seem, that the axis-fibres contain no trace of 

 fatty matter ; at all events, except that they shrink a little, they are 

 not altered by the action of ether and alcohol, and afterwards, also, 

 again enlarge, under acetic acid, into broad pale bands. Besides the 

 reagents above mentioned, the axis-fibres are particularly well displayed 

 by chromic acid (Hannover), corrosive sublimate (Purkinje, Czermak), 

 and gallic acid, but less readily in recent nerves, in which, it is true that 

 they become instantaneously manifest, although it is never, except by 

 accident, and rarely, that they can be isolated, than, especially after a 

 more prolonged immersion in those. The nerve-fibres under these cir- 

 cumstances appear contracted, the medullary sheath grumous, the axis- 

 cylinder more opaque and somewhat diminished, in chromic acid yellow- 

 ish, but in other respects exactly as above described. In the acoustic 

 nerve of the Sturgeon, Czermak, by means of corrosive sublimate, has 

 demonstrated in dividing nerve-fibres, the existence, also, of bifurcating 

 axis-cylinders. Iodine also or iodine combined with aqueous hydri- 

 odic acid (Lehmann) act very powerfully. In quite recent nerves it 

 instantaneously renders the medullary sheath wholly grumous, and not 

 only isolates numerous, somewhat shrunken axis- fibres, for a considerable 

 length, but renders them in many nerve-fibres very distinct in situ^ and 

 usually appearing convoluted or serpentine. Hydrochloric, sulphuric, 



