1905.] Distribution of Chlorides in Nerve Cells and Fibres. 185 



becomes more distinctly resolvable into granules. Further, there are now and 

 then in the striated portion of the axon short segments where the deposit is a 

 uniform one, and on either side of one of these segments the striae differ in 

 their breadth so much as to suggest that they do not belong to the same series. 



Of all these points one finds illustrations also in glass capillary tubes. 

 Further, the fusion of several striae referred to as occurring in glass tubes 

 occurs in the axons, and has been described under the term biconical swelling 

 (" renflement biconique " of Kanvier). The enlargement cannot, of course, take 

 place in a rigid tube while the medullary sheath and the neurilemma are to a 

 certain extent elastic and permit such alterations in the thickness of the axon 

 as the enlargements referred to. Boveri held that the enlargements are really 

 an extra axial or periaxial deposits of silver at the node, but the fact that we 

 can obtain such enlargements in the medullated fibres of the cord (rat, 

 guinea-pig and frog) where there are no nodes, does not lend any support to 

 this view. 



There is but one feature in the Frommann striation which we have not 

 foundiin capillary tubes, and it does not occur very frequently. This is seen 

 in a division of a single striation into two imperfectly separated halves 

 (fig. 6, b). This may be explained as due to a local condition of the nerve fibre 

 like or similar to that which in capillary tubes may result in producing an 

 interruption of the striated column. 



In view of all these facts, the Frommann striation must not be regarded 

 as an indication of the disposition of the chlorides in transversely arranged 

 zones in the nerve fibre intra vitam, but it is rather the result of the operation 

 of physical processes which in capillary tubes produce the Boehm (or Liesegang) 

 phenomenon. 



The medullary sheath is in the great majority of the nerve fibres free from 

 chlorides, but in the remainder a reaction for chlorides may be obtained at 

 points along the course of the sheath, as in the preparation represented 

 in fig. 18, which is of interest in view of the fact that a similar distribution 

 of a potassium salt has been observed occasionally,* and it would indicate that 

 chloride of potassium is present at these points. It is, however, more 

 frequently in the imbrications of Lanterman than in other parts of the 

 medullary sheath that one obtains the reactions for chlorides. One finds now 

 and then all the imbrications in a long extent of the fibre revealed by the 

 chloride reactions (fig. 19), and so fully as to bring into prominence the 

 funnel-shaped outlines of these structures (fig. 10, d). In these, also, the 

 potassium reaction was occasionally obtained and, therefore, a part at least 

 * Macallum, ' Journ. of Physiol.,' vol. 32, p. 95. 



