The Marchi Method

Abstract

An investigation has been made of the poor penetration obtained by the Marchi method. Use of surface-tension depressants or perfusion technics showed no marked improvement. Opt. results cannot be achieved with slices of tissue > 3 mm. thick. Another cause of faulty staining is the failure to maintain an adequate strength of OsO4 in the Marchi mixture. The conc. of this chemical should never be allowed to drop below 0.25%. A chemical method for deter. the amt. of OsO4 present in the staining mixture and based upon the Alvarez test is descr. This method can also be utilized to reclaim partially exhausted staining solns. Remarks are included upon the KIO3 meth. of Busch.