1905.] Distribution of Chlorides in Nerve Cells and Fibres. 181 



of the spinal cord (rat) with the reagent. In such preparations there were a 

 large number of medullated fibres which exhibited, over long stretches of 

 their axons, a striation quite as marked and as characteristic as one may 

 obtain in pressed-out preparations of the cord treated with the nitrate of 

 silver reagent. Such a striation as obtained by the mercurous nitrate 

 reagent is represented in fig. 16. Nothing approaching this has been obtained 

 with the same reagent in nerve fibres having a neurilemma. On the other 

 hand, this reagent can pass through the medulla of the fibres of the cord, 

 and give, as did the nitrate of silver, a diffuse reaction for chlorides. 



There can, therefore, be no doubt that the axon is rich in chlorides, but 

 that these cannot be demonstrated readily therein, except at the nodes, in 

 fibres provided with a neurilemmal sheath, and the difficulty is due, though 

 not wholly, to the neurilemma. When this is absent one may obtain such a 

 demonstration more or less readily, and the result appears in the form of the 

 Frommann striation or in a diffuse reaction throughout the axon. 



It is now a question whether the striation or the diffuse reaction indicates 

 the true distribution of the chlorides in the fibre. That the striation cannot 

 represent it seems to be indicated by the fact that the striae which are 

 remote from a node may be and are usually less distinct, broader and wider 

 than those in the neighbourhood of a node, and that there are degrees of 

 transition from the distinct narrow to the less deeply stained broad ones. 

 Grand ry, Joseph and Jakimovitch hold that it demonstrates a pre-existent 

 arrangement of substance in the axon, and the last named would explain 

 their presence as a necessary factor in the functional activity of nerve 

 fibres, while Boveri and Eabl regard the striation as not due to a pre-existent 

 disposition of the substance of the axon, the former explaining the striation 

 as a result of physical causes. 



A good deal of light has been thrown on the causation of this striation by 

 the discovery of Boehm* that solutions of egg-albumen in capillary glass 

 tubes, when placed in solutions of nitrate of silver, show the silver chloride 

 as a precipitate to appear as striae transversely placed in the lumen, and more 

 recently by the observations of Liesegangf on the diffusion of silver nitrate 

 in films or columns of gelatine impregnated with potassium bichromate. 

 "When a drop of nitrate of silver solution is placed on a glass plate faced 

 with a film of gelatine impregnated with the bichromate salt, the silver salt 

 diffuses slowly and in an ever-growing circular area concentric with the drop, 

 and, as it diffuses, it forms a precipitate in the gelatine of silver chromate 



* Boveri, loc. cit, gives the only account accessible of Boehm's discovery, 

 t ' Chemische Beaktionen in Gallerten,' Diisseldorf, 1898 ; also Liesegang's ' Photo. 

 Archiv,' 1896, p. 321. 



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