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P. J. Hanzlik, M.D.
JAMA. 1934;102(26):2218. doi:10.1001/jama.1934.02750260064023.
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To the Editor:—  Recent correspondence in The Journal (March 17, p. 862; April 14, p. 1246) regarding the standardization of digitalis leaves impressions that are likely to increase the dilemma of manufacturers.Pharmacologists are largely responsible for introducing, and carrying on the principal investigations in, bio-assays, but the practice of bio-assay is chiefly the concern of manufacturers of pharmaceutic products. The latter require simple, reasonably accurate and economical methods that will give reproducible results. Such methods will increase the popularity and promote the use of bio-assays.There is no doubt of the frog method being simple, but there is serious doubt of its giving accurate and dependable results. Moreover, frogs are practically unobtainable in arid and semitropical regions and importations are costly, so that an assay on frogs may actually be more expensive than on cats. However, cats too are difficult to obtain in sufficient quantities almost everywhere. Of course,


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