THE NERVOUS SYSTEM. 397 



and in other respects, also, present all the characters of those 

 fibres, only that they are much paler and broader (as much as 

 O0()4'"' in the 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 some- 

 times granules, sometimes very short rods, like fat-crystals, 

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

 ing 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 O002'" wide), yellowish, firmer, and 

 often convoluted or twisted. Ether acts in the same manner. 

 By both reagents the medullary sheaths are rendered paler and 

 grunious, 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 aud axis-cylinder perfectly dis- 

 tinct, 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 fluids. The nerve-fibres under these 



