PARTURITION 



203 



in one of his early papers, stated that contraction of the isolated 

 uterus was caused by the oestrus-producing extract. Laqueur 

 and his co-workers (356) showed that oestrin stimulated the 

 isolated uterus, and Brouha and Simonnet (103) later stated 

 that the contractions of the uterus after ovariectomy can be 

 caused to change to those typical of oestrus by the addition of 

 liquor folliculi to the bath in vitro. They ascribe this result to 

 the presence of an oxytoxic substance in the follicle rather than 

 to the action of oestrin. 

 Fraenkel (212), however, 

 found no effect on the iso- 

 lated uterus, and Bourne 

 and Burn (79) found a 

 direct action of cestrin on 

 uterine contraction in vitro 

 only when the uterus was 

 particularly sensitive. It 

 may also be pointed out 

 that Frank's view of the 

 continued action of oestrin 

 all through gestation (see 

 p. 122) is difficult to re- 

 concile with his results on 

 uterine contraction. In 

 any case it seems certain 

 that the direct effect of 



oestrin on uterine contraction is not sufficient to be of 

 any importance in parturition. The action of active corpus 

 luteum extracts on the uterus does not seem to have been 

 investigated. 



Fig. 68. — Effect of (Estrin on the 

 contraction of an isolated guinea- 

 PiG Uterus. 



(From Bourne and Burn). 



(c) ROLE OF OXYTOCIN 



Since direct action of the ovary on uterine contraction is 

 insufficient to account for parturition, it is natural to con- 

 sider if any part may be played by the oxytoxic principle 

 of the posterior pituitary body. Combining the evidence of 

 the correlation of the ovarian cycle with parturition, and the 

 evidence of the action of oxytocin on the uterus, two alternative 



