MONTREAL, CANADAHE IMPORTANCE OF PHENANTHRENE derivatives in pharmacology and physiology II is clearly shown by the fact that so many useful drugs and essential metabolites -1L belong to this group. Morphine, codeine, colchioine, the bile acids, the digitalis aglucons, the toad poisons, many carcinogenic hydrocarbons, the vitamin D group, cholesterol and the steroid hormones all possess the phenanthrene or perhydro' phenanthrene nucleus. Up to the present comparatively little attention has been given to the correlations which exist between the chemical structure and the phar' macological actions of the cyclopentano'perhydro'phenanthrene derivatives, and hence it was decided to make a systematic study of this field since an understanding of these correlations is a necessary prerequisite for any planned attempt to synthesize more potent compounds than are now available. Such an investigation was particu' larly tempting because the very important steroid hormones and their metabolites be' long to this group. The recently discovered fact (137) that hormonally active steroids, if administered intraperitoneally or intravenously, produce anesthesia in the rat, sup' plies us with a simple test revealing pharmacological activity among such compounds.In the present communication we should like to summarize the most outstanding re' suits of these investigations, which were possible only through the full'hearted CO' operation of numerous outstanding steroid chemists of many countries, who furnished us with the necessary compounds. 2 Although the main object of our study was to correlate chemical structure with the anesthetic effect of the steroids, in some cases special assays were performed to ex' amine the compounds for other hormonal actions.
EXPERIMENTAL METHODSSince it was found that the anesthetic effect of the steroids is increased by partial extirpation of the liver (138), apparently because they are normally detoxified in this organ, we performed our assays in the partially hepatectomized rat. In order to facilitate a comparative study, it appeared desirable to establish a R.U. of anesthetic effect. This anesthetic rat unit (A.R.U.) is defined as the minimum amount of a steroid which, when injected intraperitoneally, causes loss of the righting reflex in 4 of 6 female rats