ON THE ENDOCRINE BASIS OF MATING IN THE MOUSE

1. No mating was observed in untreated ovariotomised mice. 2. Mating was induced in ovariotomised mice by injections of follicular juice; but injections of aqueous extracts from this material did not induce mating. 3. Mating was induced in eleven out of twenty ovariotomised mice by injections of cornifying extracts prepared from pregnancy urine. 5. Mating is assumed to be an effect of the cornifying a-factor conditioned by a higher threshold than cornification. 5. The relation of the thresholds is discussed with reference to its possible variation. 6. Questions of terminology are discussed and the term a-factor or ALLEN-DOISY factor is adopted.