ii6 INTERNAL SECRETIONS OF THE OVARY 



(but see 436). During the time when oestrus is normally in 

 abeyance (except in the very young animal), the injection of the 

 intact animal with adequate amounts of oestrin results in the 

 appearance of extra-ovarian oestrus At certain times, how- 

 ever, notably when functional corpora lutea are present in 

 the ovary, considerable dosage is required to bring on this effect. 

 No ovarian changes characteristic of oestrus occur during such 

 an induced period (see p. 119 for non-effect of oestrin on follicular 

 maturation). 



. Prenatal period. Since the administration of large amounts of 

 oestrin during pregnancy leads to reabsorption or abortion, it- 

 is not possible to subject the foetuses to an excessive additional 

 oestrous stimulus, even if it is assumed that oestrin will cross the 

 placenta. Working with amounts insufficient to produce 

 abortion, Courrier (133) claimed to find growth effects on the 

 foetal uteri after injection of the pregnant guinea-pig. Allen, 

 Francis, and Craig (23), and Parkes and Bellerby (504) were 

 unable to confirm these results on the rat and mouse, while 

 negative results have also been obtained by Loeb (404) on the 

 guinea-pig. Eels (202) claims to have found oestrin in foetal 

 blood. In view of the large amounts of oestrin in the circulating 

 blood of the pregnant female (see p. 109), the passage of oestrin 

 across the placenta would mean that all foetuses, including the 

 males, would develop under the influence of this hormone. 

 Courrier 's result is therefore improbable. Parkes and Bellerby 

 (504), in fact, found that the uterus of the new-born mouse did 

 not react to oestrin. 



The pre-pubertal animal. The effect of oestrin injection on the 

 normal pre-pubertal animal has already been indicated in 

 discussing the use of such animals for testing (see p. 93 and 

 also p. 97). In the rat and mouse rapid proliferation of the 

 vaginal epithelium is produced and the vaginal orifice appears. 

 The uterus shows the typical distension, with change of the 

 undeveloped epithelium to a low columnar type. According to 

 Brouha and Simonnet (90) the mammary gland shows no 

 change. Since the same oestrous reaction is found in the ovariec- 

 tomized immature animal, it is clearly independent of any 

 primary effect upon the existing ovary. 



Loeb (405) has produced similar oestrous changes by injection 



