The stability of watery solutions of the oxytocic principle of the pituitary gland.

IT has long been known that the substance in the posterior lobe of the pituitary gland which produces contractions of the uterus is destroyed by alkalis in the cold [Guggenheim, 1914], is stable in weakly acid watery solution, and is destroyed by boiling in strong acids [Abel and Nagayama, 1920; Dale and Dudley, 1921]. Adams [1917] showed that when weakly acid extracts were heated the oxytocic activity, measured on the guinea-pig's uterus, disappeared from the solution in such a way that its rate of disappearance at any moment was proportional to the activity present at that moment. The solutions were much more stable at PH 3 than at pH 5. This paper deals with a number of determinations which have been carried out, under my direction, by my assistant, L. S. Drewell, with the object of obtaining more complete -quantitative knowledge of the stability of this substance. Buffered extracts were prepared from the British standard preparation of the posterior lobe, heated for different times and assayed. The tests were carried out on the virgin guinea-pig's uterus by the method described by Dale and Laidlaw [1912], the details of the apparatus being those described by Burn and Dale [1922]. The results are comparable with, and in many ways similar to, the results obtained by Krogh and Hemmingsen [1928] in their study of the action of heat on insulin. For the sake of uniformity the notation of these authors has been adopted in the present paper.