524 REPORT— 1897. 



necessarily show in every fibre.) At some nodes there may be seen a 

 slight approximation of the myelin on each side towards the centre of the 

 node. Besides this, in several fibres, instead of the medullary sheath end- 

 ing in a rounded extremity at the node, it seems to flow along the axis 

 cylinder from one side to meet the myelin of the opposite side, producing 

 an appearance fitly described by the term * the waist effect.' In specimens 

 fixed in osmic vapour, and subsequently treated with carmalum, the axis 

 cylinder is seen to traverse the node, and to be apparently there ensheathed 

 by a delicate darkened covering continuous with the medullary sheath on 

 each side of it. This would seem to indicate that there is actual fusion of 

 the myelin of opposite sides across the node. In the smaller fibres the 

 change may be so marked as to almost obliterate the appearance of the 

 node. The ' waist effect ' is seen in many fibres usually, the approxima- 

 tion perhaps in but few. 



The nodal effect becomes visible after 1-2 minutes of administration^ 

 and is usually marked after 2|-3 minutes. 



Etherised fibres do not reduce osmic acid so readily as normal fibres — 

 i.e., they do not colour so deeply. 



Carbonic acid produces appearances in nerve very similar to etherised 

 nerve, but rarely to such a marked extent. We find much the same 

 appearances in the nodes ; granularity may be entirely absent. When 

 present, it is usually coarse ; the incisures are even more distinct than 

 in etherised nerve. In one or two cases the appearance has been so* 

 marked as to give distinct prominence to the myelin opposite the 

 incisures, the fibre having a knotted appearance comparable to that of a 

 bamboo cane. 



The CO2 effect is usually visible after two minutes' administration, 



CO2 nerves stain readily with osmic vapour. The consistence of the 

 myelin seems to be somewhat altered by action of the CO2, the medullary 

 sheath tending to break up under manipulation rather more than a, 

 normal nerve would under similar treatment. 



Chloroform Vapour. — As in etherised nerve, granularity may be 

 observed. It is of a somewhat finer nature than the granulation due to^ 

 ether, and appears somewhat later. 



On examination of a fresh preparation, simultaneously with the 

 administration of the vapour, there is sometimes seen comparatively early 

 a slight approximation of the medullary sheaths at the nodes, followed hj 

 a gradual separation commencing shortly after, and reaching its height in 

 about two to two and a half minutes. 



On fixing with osmic vapour, the darkening of the myelin shows at the 

 nodes a distinct gap, visible plainly even under the low power. The 

 medulla seems to taper along the axis cylinder for some distance on either 

 side, and terminates in a ragged edge, which seems to suggest fusion with 

 subsequent separation. Other nodes may, however, show no such tapering 

 appearance, the medulla merely being retracted from the node. 



Provided that time has been given for the vapour to penetrate, the 

 majority of fibres in a chloroformed nerve show the change, which is 

 usually far more marked and more constant than the change in etherised 

 or ' carbonised ' nerve. 



The chloroformed nerve does not stain quite so deeply with osmic 

 vapour, as a normal fibre exposed for a similar time. 



The consistence of the myelin seems to be altered, it seems to become 



