1905.] Distribution of Chlorides in Nerve Cells and Fibres. 167 



II. — Historical Account of the Literature of the Subject. 



There are no observations, in the literature dealing with nerve fibres, 

 which bear directly on the occurrence of chlorides in these structures. 

 There are incidental, and often indefinite statements, referring to the forma- 

 tion of chloride of silver in the axons of nerves, as, for instance, that of 

 Boveri* when explaining the production of Frommann's lines, but elsewhere 

 in the same work he attributes the silver reaction of nerves not to the 

 presence of any specific substance or compound, but to a precipitate brought 

 about by and in the contact surfaces of tissue elements. 



Nitrate of silver has, however, been employed in the study of nerve fibres 

 since 1864, the year in which Frommann made his observations! with that 

 reagent on nerve cells and fibres, and to the results of its use we owe a 

 clearer understanding of the structure of the nerve fibre than we would have 

 without its service. These results were attributed either to physical factors 

 operating on the silver salt and producing a new compound of it which 

 reduced in light, or to an organic compound uniting with the silver to form 

 a combination also affected similarly by light. Kanvier, who made a very 

 extensive use of the reagent, curiously refrains from expressing any view 

 as to the mode of action of the salt, or even as to the possibility of an 

 explanation of its action. 



Though the action of the silver nitrate on nerve fibres was unexplained 

 and unknown, yet its use brought out results of importance which, in the 

 light of what we now know, are to be understood as due to the presence of 

 chlorides in the parts affected. Of course the indications which they give 

 of the distribution of the chlorides are very inadequate and very often 

 faulty, but they have furnished some conceptions of the structure of the 

 fibres, and on this account a summary of some of them comes in properly 

 here. 



Frommann, on using a solution containing from \ to 1 grain of silver 

 nitrate to the ounce on nerve fibres of the spinal cord, found on exposure to 

 light a yellow or brown coloration of the axis cylinders. Some had a 

 homogeneous or very finely granular appearance, others appeared distinctly 

 striated transversely, the stria? being placed close to one another. These 

 striae sometimes obtained throughout the whole visible portion of the fibre, 

 sometimes again only in a portion of the same, the striae at the terminal 



* "Beitrage zur Kenntiiis der Nervenfasern," 'Abhandl. d. k. Bayer. Akad., Math. - 

 Phys. CI.,' vol. 15, 1886, p. 423. 



t " Zur Silberfarbung der Axencylinder," ' Virchow's Arch.,' vol. 31, 1864, p. 151 ; also 

 " liber die Farbung der Binde und Nervensubstanz des Blickenmarkes durch Argent um 

 nitricuni und uber die Struktur der Nervenzellen," same volume, p. 129. 



N 2 



