By the careful control of the pH of the silver proteinate impregnating solution by addition of variable quantities of M/5 boric acid buffer and by varying the amount of copper added, enterochromaffin cells could be selectively impregnated by the Bodian method. Impregnation in this solution was followed by exactly the same procedure as in Bodian''s original method except that the time of treatment in the final oxalic acid bath was carefully controlled to prevent overstating of other tissue elements. For foetuses older than 80 mm C.R., length and for adult tissues the addition of 12 ml of M/5 boric acid and of 6 g of copper per 100 ml of the impregnating solution was found to give an intense impregnation of the enterochromaffin cells with only slight staining of other tissue elements providing very good contrast For younger foetuses, however, lesser amounts of the boric acid solution and of copper were found to yield the most satisfactory results.