1905.] Distribution of Chlorides in Nerve- Cells and Fibres. 173 



glycerine of 50 per cent, strength and exposed to the action of bright sunlight 

 till the maximum effect was obtained. 



In making preparations of the spinal cord a portion of the latter was 

 pressed out between two glass slides to a very thin layer and this, attached to 

 one of the slides, was placed in the reagent for 24 hours, after which it was 

 exposed to light, mounted in glycerine and covered. This was found to be 

 the best way of preparing, with the silver reagent, nerve fibres unprovided 

 with a neurilemma, and it gave some very good preparations of nerve cells 

 showing the distribution of chlorides in them. 



Nitrate of silver, when alone in solution, does not penetrate very well, and 

 thus, in the remote parts of even a minutely teased-out preparation, there 

 may be a redistribution of the chlorides before the reagent has reached them 

 by diffusion. When free nitric acid is present, it promotes considerably the 

 diffusion of the nitrate, but, unfortunately, the acid diffuses more readily than 

 the salt, and, in consequence, if the preparations are not carefully teased out, 

 the result may be the same as when the reagent is neutral. 



We have used solutions of the reagent containing less than 1 per cent, of 

 the salt with as much as 10 per cent, of the acid. It was found that such a 

 solution gave, in the majority of instances, the most marked preparations of 

 the axons with Frommann's lines, the latter often extending over the axon 

 for the whole, or nearly the whole, extent of the internodal segments of the 

 fibre. This solution, however, has the disadvantage of redistributing chlorides 

 before the silver nitrate reaches them. Instances of this were found in 

 nerve fibres of the sciatic of the frog and rat in which a portion of the 

 chlorides diffused, in the parts remote from the nodes, from the axon into 

 the medullary sheath, and were then precipitated by the reagent. It was 

 observed also that the reagent of this composition gave very often in ordinary 

 connective tissues, as, for instance, in those of the pancreas of the guinea-pig, 

 in the adventitia of arterioles, and in the gastric mucosa of the frog, a 

 striation in every respect like that found in the axons, and exactly similar to 

 that described by Eabl in such structures. Such striations are artefacts, and, 

 therefore, a high degree of concentration of acid in the reagent tends to show 

 a distribution of the chlorides that does not obtain in the living fresh 

 structures. 



The best results are so obtained, as our experience shows, with a deci- 

 normal solution of the salt containing 1*5 per cent, nitric acid. When the 

 preparations had been acted on by it for the required time, they were 

 mounted, without removing the excess of the reagent, in 50 per cent, 

 glycerine. The advantage in this is that, as in the photographic plate, an 

 excess of nitrate of silver acts as a "sensitizer," that is, it combines with 



