Chapter W 



Silver 

 Impregnation I 



RETICULUM TECHNICS 



Silver Impregnation 



According to Baker (1958) methods tinder this heading depend upon 

 the local formation within tissues ot a colored substance Avhich is not a 

 dye. Impregnation applies to a condition developing Avhen an tni- 

 rediiced metal (silver, etc.) is taken up from a solution of salt or other 

 compound and deposited, in a colloidal state on a tissue element. Eol low- 

 ing impregnation, the tissue is removed to a reducing solution of a 

 photographic type and the metal is reduced to the elementary state, 

 probably in the form of a black deposit. Thus the tissue itself does not 

 reduce the metal, but some extraneous reducer is reqtiired to perform 

 the reaction. 



Silver staining goes back as far as 1843 when Krause tried small pieces 

 of fresh tissue in silver nitrate. The Golgi method appeared in 1873. 

 Ramon y Cajal [1903, 1910) first experimented wath silver nitrate in 

 1881 and tried reducing it. Also in the early 1900s protargol (Bodian 

 method) and other organic silver compotuids were introduced as sub- 

 stitutes for silver nitrate. The albumen fraction in the organic com- 

 potuids is considered to act as a protective colloid which prevents too 



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