ITS MICRO-CHEMICAL RELATIONS. 103 



at most the membrane is rendered somewhat more hyaline and the 

 contents rather more grumous. 



Concentrated hydrochloric acid does not bring into view the 

 individual morphological elements either in the fibres or the cells ; 

 but converts the whole into a pultaceous mass of smaller or larger 

 strongly granulated dark clots, which, although most commonly 

 roundish, may assume the most varied and capricious forms. If 

 any remains of nerve-fibres are present, they are found to be very 

 much thickened ; the dark clots are perfectly isolated and arranged 

 only in one direction, and no trace of a nerve-sheath is perceptible. 

 When a freshly prepared microscopical preparation is treated with 

 concentrated hydrochloric acid, the individual nerve-fibres diminish 

 in length, but increase to an extraordinary degree in breadth ; the 

 nerve-pulp becomes coarsely granular and dark, whilst from the 

 cut extremities nodular or coarsely granular masses protrude, and 

 most distinctly bring into view the coiled roundish threads or axis- 

 cylinders. In this way more frequently than by any other method 

 of exhibiting the axis-cylinder, I have been able to see the sheath 

 and nerve-pulp dissolve in the middle of a fibre, leaving only the 

 axis-cylinder, which at these points might be traced in both 

 directions through the comparatively uninjured nerve-fibre. The 

 peculiar property of concentrated hydrochloric acid in simulta- 

 neously thickening and shortening the nerve-fibre is beautifully 

 illustrated in small bundles of nervous fibres, which are surrounded 

 by the neurolemma. The latter varies in expansibility according to 

 the amount of connective or elastic fibres which it contains. When, 

 therefore, the nerve-tubes which it encloses are much swollen, 

 several protuberant dilatations and corresponding constrictions 

 appear in one and the same bundle. The fibres projecting from 

 the neurolemma at the extremities of the bundles diverge in a 

 brush-like form, whilst the nerve-pulp protrudes from the cut 

 extremities of the fibres, giving to the whole a bouquet-like 

 appearance. 



When fresh nerve-fibres are allowed to remain for some time 

 immersed in concentrated nitric acid, the whole mass becomes 

 intensely yellow and very friable or soft. On observing under the 

 microscope the direct action of nitric acid, we find that the indi- 

 vidual fibres are thickened and shortened as in the case of concen- 

 trated hydrochloric acid, although in a less degree. The double 

 contours cease to be recognisable in fibres which have been treated 

 for a longer period with nitric acid ; the whole contents of the 

 nerves appear coarsely granulated, and we can perceive no light 



