172 



Prof. A. B. Macalluin and Miss M. L. Menten. 



[July 24, 



are the expressiqn of periaxial, not intraaxial, structures, and amongst these 

 may be mentioned Kumpf,* Morochowetz,| Obersteimer,| Lavdowsky§ and 

 SchiefferdeckerJI but the deposit which gives the appearance of the striation 

 is, according to Jakimovitchf and Eabl ,** distributed uniformly throughout the 

 whole transectional area of the axon. 



III. — Methods of Investigation. 



As already pointed out, it has been shown by one of us that nitrate of silver 

 in the presence of free nitric acid constitutes, in the absence of creatm 

 and taurin, a very sensitive reagent for chlorides, if the preparations are 

 subsequently exposed to light, and that proteids and albuminoids free from 

 chlorides do not give any compound with a silver salt which can be " reduced " 

 in the sunlight. 



As a consequence of this discovery the reagent has been used very 

 extensively by us to determine the distribution of the chlorides in the axon. 

 The solution used was a decinormal one of the nitrate, to which 25 c.c. of 

 nitric acid of 1*4 specific gravity (i.e., 60 per cent, strength) were added for 

 every 1000 c.c. of the solution. The reagent, therefore, contained 17 per 

 cent, of silver nitrate with 1*5 per cent, of free nitric acid. The distilled 

 water used in making the solution was free from chlorides to the extent that 

 the reagent, when kept in the sunlight for months, did not give the slightest 

 indication of an opalescence, discoloration, precipitate or deposit. This is a 

 point of importance, for the reagent will reveal the presence of chlorine as. 

 chlorides when the chlorine is as dilute as 1 in l,600,000.ft 



The tissues treated were in every case perfectly fresh and, in order that the 

 penetration should be quickly obtained, the parts were carefully and finely 

 teased out on the slide or in the dish before the reagent was added. The 

 latter was allowed to act for a time which in individual cases varied from 

 1 to 48 hours, and while in the bath of the reagent the preparation was 

 protected from the light. Then it was, when necessary, still further teased 

 out, either quill or glass points being used for this purpose, finally mounted in 



* ' Untersuchungen aus dem Physiol. lust, zu Heidelberg,' vol. 11, 1882. The reference 

 is given by Eabl. 

 t Eabl, loc. cit. 



% ' Anleitung beim Studiuni des Baues der nervoseu Centralorgane,' Leipzig und Wien, 

 1888. 



§ ' Journ. de Medecine Militaire,' 1884-5. The reference is given by Eabl. 



|| " Beitrage zur Kenntniss des Baues der Nervenfasern," ' Arch, fiir Mikr. Anat. ' 

 vol. 30, p. 435. 



1 Loc. cit. 

 ** Loc. cit. 

 ft Macallum, loc. cit 



