Histochemists have acknowledged the need for quantitation in their discipline, and a majority of them report their histochemical findings with some quantitative information (Anderson & Glenner, 1973; Rosenquist, 1976). It seems to be the consensus of the histochemistry fraternity that 'direct' histochemical quantitation is the most satisfactory method, wherein the amount or intensity of stain is obtained directly from stained sections. The commonest method for obtaining direct and objective quantification has been microdensitometry (Rosenquist, 1976). Altman (1975) has reviewed some aspects of microdensitometry and its great potential in histochemistry; he said that: 'a perusal of current histochemical journals will show that the technique is being increasingly used, compared to only a few years ago'. On analysing the more widely-used histochemistry journals, the contrary was found namely that the use of direct quantitation had apparently not increased (Rosenquist, 1976). I concluded, as my colleagues and I had done before (Rosenquist & Rosenquist, t974a; Troyer & Rosenquist, 1975), that the use ofmicrodensitometry was limited by its general unavailability and high cost. In contrast, atomic absorption spectro-