186 Prof. A. B. Macallum and Miss M. L. Menten. [July 24, 



of the quantity of the chlorine present as chlorides must occur as potassium 

 chloride. 



The fact that this salt occasionally occurs in the imbrications, is an 

 indication that these are the weak points in the sheath through which the 

 salts of the lymph bathing the nerve fibres can penetrate to the axon. 

 Indeed, as already stated, an imbrication may be the point of entrance for 

 the reagent to bring out the Frommann striation (fig. 13, a). The double 

 character of each of the imbrication funnels seems to show that the chlorides 

 do not obtain so much in the cavity of the clefts of the imbrications as in 

 their walls. 



The absence of chlorides from the rest of the medullary sheath in the 

 normal nerve fibre is noteworthy, and can be interpreted as signifying that the 

 medulla is a very effective barrier to the passage, on the one hand, of chlorides 

 from without the nerve fibre and, on the other, of the haloid salt from the 

 deeply charged axon into the contiguous fat-holding neurokeratin network. 

 The retention of the chloride in the axon must in very large part, if not 

 wholly, be due to the property of the sheath. 



B. In Nerve Cells. — Frommann, G-randry, and Jakimovitch found that 

 nerve cells give a reaction with silver salts like that which may be obtained 

 in the nerve fibre, but Frommann found that it was a diffuse one in the 

 cytoplasm, more or less implicating the nucleus and the nucleolus, while the 

 two last named observers obtained in their preparations a transverse striation 

 of the nerve cells like, in every respect, that occurring in the axons, and 

 apparently constituting a continuation of it. 



The occurrence of a striation has been observed by us in a few of the nerve 

 cells from the anterior horn of grey matter of the spinal cord of the frog and 

 guinea-pig, the striation affecting, in the majority of instances observed, only 

 a portion of the cell, and appearing to be an extension of the striation from 

 one of the polar processes of the cell. The nucleus was in not one instance 

 affected, and when it appeared to be, it was found that the result was really 

 due to the colour reaction of the cytoplasm above or under the plane of the 

 nucleus. 



These instances of striation of the nerve cell were exceptional cases. In 

 the pressed-out preparations of the spinal cord treated with the acid nitrate 

 of silver solution for 24 hours, when the nerve cells were affected they 

 usually showed a brownish-yellow reaction of the cytoplasm, but an absolutely 

 uncoloured nucleus and nucleolus. The reaction was a diffuse one, but some- 

 times so far particularised as to give the appearance of a longitudinal striation, 

 suggesting a slight degree of fibrillation, yet in no case was it marked enough 

 to indicate that it was anything more than an artefact. A more pronounced 



