Improvement of the Golgi Method by pH Control

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Abstract
Experiments were made to test the influence of the pH of the fixing fluid (ranging from 1.0–8.1) and that of the chromating fluid (1.65–7.8) on subsequent silver impregnation. Brains of adult monkeys, cats, dogs, rabbits, guinea pigs, rats and mice were fixed by the pulsating-perfusion method of Haushalter and Bertram (1955), after first washing out the blood with saline-acacia solution of the same pH as that of the 10% formol-saline-acacia used for fixation. The brains were sliced to 3 mm thickness and the slices further fixed 1–2 days in 10% formalin with its pH adjusted to that of the preceding fixing fluid. Chromation for 1 day followed, with acidified ZnCrO4 at pH 1.65-5.9 and buffered Na2CrO4 at pH 7.8. Silvering for 2 days in 0.75% AgNO3 solution effected the staining. Dehydration, paraffin embedding and sectioning completed the process. From these experiments, it was found that fixation at pH 7.0–7.2 followed by chromation at pH 3.1 in a mixture of ZnCrO4, 60 gm and formic acid, 35 ml, diluted to 1000 ml with distilled water, was optimum for best impregnation of nerve cells and their processes. Human brain and that of newborn mammals, although not perfused, responded well to the controlled-pH procedure. The advantages of the technic are the staining of nerve cells in regions refractory to previous methods and the relatively short time needed for its completion.