510 Dr. J. E. Lane-Claypon and Prof. E. H. Starling. [Feb. 12, 



chemical excitant by the ovaries, or to the changed metabolism of the uterus 

 during pregnancy, or whether the new products of conception, namely, the 

 foetus and placenta, represent the seats for the manufacture of the mammary 

 hormone. 



There is a large amount of clinical evidence which enables us to decide 

 with some probability, though without certainty, between these various 

 alternatives. Conception is followed by a great increase in the size of the 

 ovaries, chiefly in consequence of the formation of the corpus luteum. This 

 growth has been associated by Born, Fiu-nkel,* and Marshallf with the 

 production of a specific excitant for the uterine mucous membrane which 

 determines the growth of this membrane and the attachment of the embryo. 

 These observers have shown that extirpation of both ovaries at an early 

 period in pregnancy, or even destruction of the corpora lutea by means of 

 the cautery, causes the cessation of the pregnancy. We ourselves have found 

 that extirpation of both ovaries in the rabbit if carried out before the 15th 

 day is apt to cause abortion. Later on in pregnancy oophorectomy can be 

 performed without interfering with the course of the pregnancy. 



The growth of the ovaries is, however, chiefly marked in the first third or 

 half of pregnancy. After this time the corpora hdca begin to diminish in 

 size, and with them the whole ovaries. On the other hand, the growth of the 

 mammary gland, although marked almost immediately after impregnation, 

 becomes more and more rapid with the advance in pregnancy, and the 

 growth during the last half of pregnancy is many times greater than that 

 during the first half. Moreover, numberless instances in man show that 

 extirpation of both ovaries, as in double ovariotomy, does not necessarily 

 interfere with the course of pregnancy or with the growth of the mammary 

 glands. Labour may come on at the usual time, and be followed by normal 

 lactation. 



The fact that the mammary glands undergo normal hypertrophy in extra- 

 uterine fcetation, where the growth of the uterus is only a small fraction of 

 that occurring under normal circumstances, seems to point to the products 

 of conception, -i.e., either the foetus or placenta, or both, as the seats of origin 

 of the mammary hormone. This conclusion is borne out by the fact that in 

 extra-uterine fcetation, if the death of the foetus occurs, this event is followed 

 within a few days by the appearance of milk in the hypertrophied gland. 

 The same result occurs when the death of the foetus happens /'// i it-cm some 

 time before its expulsion. On the other hand, as mentioned in the earlier 

 part of this paper, cases have been recorded in which the death of the fret us 



* 'Arch. f. Gyu.,' vol. 68, 1903. 

 t Loc. cit. 



