14 Mr. J. S. Macdonald. [July 31, 



Nerve-fibres Teased in " Normal Saline " Tinged with Toluidine Blue. 



I have, in a previous note, described the manner in which these nerve- 

 fibres are affected by the addition of neutral red to the " normal saline " in 

 which they were teased. This dye characteristically stains all injured points 

 and some of the nodes of Kanvier. As time elapses it also stains granules 

 which form at gradually increasing distances from these points. The most 

 notable fact about neutral red staining is the slow invasion of the nerve- 

 fibre by this process of granule formation. When I first replaced this basic 

 dye by another one of an apparently not very different character — toluidine 

 blue — I was surprised by the complete difference in result obtained. It is 

 true that here and there some stained plugs of material were visible at 

 injured points, but I failed to find any trace of the progressive granule 

 formation so evident in the other case. The characteristic effects of 

 toluidine blue staining were obtained in quite another region of the teased 

 nerve-fibres, and had a very different character. This dye stains all those 

 regions of the nerve-fibre in which the coagulative changes occur, whereas 

 neutral red yields a picture of a slowly progressing change gradually 

 affecting that first portion of the nerve-fibre in which the intramyelin 

 material is at first seen homogeneous and transparent. 



In these regions of coagulative change toluidine blue gives rise to 

 appearances which vary pari passu with the extension, and with the 

 intensity, of the coagulation present. Eegions such as in unstained fibres 

 would be definitely granular, are loaded with blue granules distributed with 

 much precision across and along the intramyelin material. Such granules 

 leap suddenly into sight over long stretches of the fibre, and are not 

 originated therefore by any process which can be described as an invasion. 

 The tract of developed granules is bounded on the side nearer to the injury 

 by a clear, unstained and homogeneous region, the line of demarcation is 

 sometimes remarkably sharp. On the other side the granular tract passes 

 into a region in which coagulative changes have led to the development of 

 a central rope now stained an intense blue colour. 



This curiously complementary behaviour of these two basic dyes is there- 

 fore of obvious interest in mapping out two different tracts of the teased 

 nerve-fibre. It certainly does not diminish this interest that in case of either 

 dye an appropriate adjustment in the saline solution in which the dye 

 is introduced to the nerve-fibre may be made to overcome this dissimilarity. 

 If Einger's solution is substituted for " normal saline," or, better still, if a small 

 quantity of sodium carbonate, 0*02 per cent., is added to the Einger, or even 

 when the sodium carbonate is simply added to " normal saline," or even when 



