Method IX 6i 



volumes of the 3.5 per cent, potassium bichromate solution (B) for 

 2-5 days. Renew the fluid after the first 12 hours. 



The action of the bichromate solution may be hastened by 

 exposing the vessel to a temperature of 38-40° C. for 12 hours, 

 then renew the fluid, and set aside for a day or two. 



3. Thence, ior impregnation, transfer to the silver nitrate solu- 

 tion and further proceed to imbed, section, clear, and mount 

 precisely as instructed for the "rapid method," 3, 4, and 5 

 inclusive. 



DOUBLE IMPREGNATION. 



The Golgi method, in any of its modifications, is frequently 

 unsuccessful. If, after the usual time has elapsed, the prelimi- 

 nary examination shows that the material is not well impreg- 

 nated, the pieces may be transferred from the silver nitrate solu- 

 tion (C) back to the potassium bichromate solution (B) and 

 placed in the dark 2 or 3 days, when they are returned to fresh 

 silver solution for 36-48 hours.' Thence proceed to imbed and 

 section as before. 



Only when the material is valuable is it advised to attempt 

 double impregnation. Otherwise, in case of failure begin again 

 with fresh material. 



Among the more important modifications of the Golgi 

 method, that of Cox'' should be referred to. His method gives 

 an impregnation by the use of mercuric chloride instead of silver 

 nitrate. Among other investigators, Strong^ and Kopsch* substi- 

 tute formaldehyde for the osmic acid in the fixing fluid for the 

 "rapid method." Failures to obtain good, clear preparations, 

 however, seem to be more frequent with this use of formal- 

 dehyde. 



■Ram6n y Cajal, Anat. Anz.j Bd. V, 1890 ; or Zett. /. wiss. Mikros., Bd. VII, 

 H. z, 1890. 



°Cox, " Impragnation des centralen Nervensystems rait Quecksilbersalzen," Arch, 

 f.mik. Anat., Bd. XXXVII, T. 2, 1891. 



3STR0NG, Anat. Anz., Bd. X, 1895. ■•KOPSCH, Anat Anz., Bd. XI, 1896. 



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