I04 INTRODUCTION TO SEXUAL PHYSIOLOGY 



of the corpora liitea is correlated with ])ronounced uterine and 

 mammary hypertropliy in the manner already described as 

 constituting pseudo-pregnancy. There can be no doubt that 

 these changes are essentially similar to those which take place 

 in true pregnancy, and consequently that the corpus luteum is 

 the organ which is responsible for these changes in normal 

 gestation. 



That the ovary with its contained corpus luteum may be 

 removed in the latter part of pregnancy in women, as well as in 

 some animals, without causing abortion, is explained by Fraenkel 

 as due to the corpus luteum being in a state of commencing 

 involution and no longer functional, the uterine mucosa being 

 already sufficiently built up to admit of foetal nutrition being 

 maintained. The effect of ovariotomy late in pregnancy upon 

 the mammary glands, however, is still uncertain, but Hammond 

 has shown that in the rabbit the growth of the mammary glands 

 is under the influence of the corpus luteum throughout the whole 

 of gestation. 



In the virgin rabbit the mammae are limited to a few ducts 

 in the immediate neighbourhood of the nipple, but as soon as the 

 corpus luteum is formed hypertrophy sets in. The mammary 

 glands of pseudo-pregnancy (which in this animal only occurs 

 under experimental conditions after a sterile copulation) do 

 not develop to the same extent as with true pregnancy. It is 

 to be noted that in the marsupial cat (Hill and O'Donoghue) and 

 the opossum (Hartman) as well as in the bitch (Marshall and 

 Halman) the uterus and mammary glands undergo hypertrophy 

 during pseudo-pregnancy in the same kind of way, but usually 

 to a less degree than they do during gestation ; milk secretion, 

 however, generally follows. Thus, even in virgin bitches milk is 

 frequently secreted at the close of pseudo-pregnancy when the 

 corpora lutea are undergoing involution, and many instances are 

 recorded of such animals suckling litters of pups produced by 

 other individuals (Heape, Paton, Blair Bell, etc.). In these 

 animals which ovulate spontaneously pseudo-pregnancy may be 

 regarded as a normal state if the ova are not fertilised at oestrus, 

 and the series of changes is to be regarded as homologous under 

 the two conditions, the difference being that in the absence of true 

 })regnancy the development of the uterus and mammae is futile, 

 owing to the absence of an embryo. In polyoestrous animals, 



