THE RELATION OF THE ANTERIOR LOBE OF THE PITUITARY TO OVULATION IN THE RABBIT

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Abstract
Of the three methods of establishing the humoral interpretation of co‐ordination between coitus and ovulation as specified earlier in this communication only the first is self‐sufficient. The second and third are complementary and mutually dependent. In so far as the experiments recorded here show that the injection of pituitary extracts evokes a response which is similar to that which follows coitus both qualitatively and with respect to its time relations, they bear upon the third method of investigation alone. It is claimed that the results obtained are due to the direct action of an anterior lobe hormone upon the ovary.Two objections which might be raised against this claim must be faced. One is that rupture of follicles in these experiments may have been due to some non‐specific substance such as histamine, inducing vasomotor changes in the follicle as suggested by Heape [1905]. A series of experiments on the injection of extracts prepared from dried gland which had undergone prolonged extraction with alcohol gave the same results as were obtained from the fresh gland, and blood‐pressure tracings of the effect of injecting extracts yielded negative results.During the experiments no definite physiological changes other than that of increased respiration was observed to follow injection of volumes of extract equal to or larger than those used above. The property of increasing the respiration rate is, however, one which is characteristic of most tissue extracts. The second is whether the ovulation‐producing substance is specific for anterior lobe pituitary tissue. Extracts prepared from a variety of mammalian organs have failed to show any action upon the ovary. It has been found, however, that ovulation can be induced by the intravenous injection of the urine of pregnant women [Friedman, 1929; Jares, 1930; Snyder and Wislocki, 1931]. Until it is shown that the ovulation‐producing substance in urine is either (a) identical with that elaborated by the anterior lobe of the pituitary and that it is excreted by the kidneys, or (b) an entirely different substance, little can be said as to whether these observations invalidate any claims made as to the specific function of the anterior lobe.From the data already elicited the most likely hypothesis is stillthat which was previously advanced by the writer [Bellerby, 1929], “following copulation or the orgasm resulting from it, the anterior lobe of the pituitary secretes a hormone which initiates in the follicle those secretory changes which finally result in its rupture.” At present little can be said with regard to the nervous factor initiating secretion of the gland. That ovulation occurs as a result of one doe “jumping” another and that it does not follow as a result of artificial insemination definitely excludes direct stimulation of nerve endings in the uterus or vagina or stimulation arising from the presence of semen in the latter organ. On the other hand, one cannot say whether secretion is initiated a a result of generalised sexual excitement involving several receptor fields, or whether it is induced specifically by tactile stimulation of nerve endings involved in the clasping of the body of one animal by the forelegs of another during posturing. Several observations have been made which substantiate the above hypothesis. Fee and Parkes [1929] found that ovulation did not occur in the decerebrate and hypophysectomised rabbit provided that the operation was carried out within an hour of mating. Smith and White [1931], using a greatly improved method of hypophysectomy which enabled them to keep their animals alive for a considerable time after removal of the pituitary, demonstrated that ovulation and development of the corpus luteum did not occur in the hypophysectomised doe rabbit.My best thanks are due to Prof. H. Florey for having carried out the hypophysectomy operations.

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