1012 



SPERM, OVA, AND PREGNANCY 



14 

 PREGNANCY 



Fig. 16.35. Dilation and ten.sile strength of the uterine cervLx of the rat during estrus, 

 pregnancy, and 2 days postpartum. The dihition of the cervix in mm. of stretch per 50 gm. 

 of added weight. The tensile strength is expressed in grams force necessary to tear 1 mg. 

 cervical tissue in a rat weighing 100 gm. E = estrus; P = parturition. (From J. Yochim and 

 M. X. Zarrow, Fed. Proc, 18, 174, 1959.) 



crease in dilatability when 5 fxg. estradiol 

 cyclopentylpropionate were given, and a de- 

 crease when 50 /Ag. were given. Progesterone 

 had no consistent effect either alone or in 

 estrogen-primed animals. Relaxin alone 

 caused some softening of the cervix, but 

 gave a maximal effect only when given with 

 progesterone in estrogen-primed animals. 

 Normal cervical dilation was also obtained 

 in pregnant rats castrated the 15th day of 

 gestation and maintained with progesterone, 

 estradiol, and relaxin (Kroc, Steinetz and 

 Beach, 1959; Yochim and Zarrow, 1959). 

 Data on dilation of the uterine cervix of the 



mouse are rather sparse; nevertheless, sof- 

 tening of the cervix with relaxin has been 

 reported (Kroc, Steinetz and Beach, 1959). 

 It is not the purpose of this review to 

 evaluate the data on cervical softening in 

 the human female. The nature of the action 

 of relaxin in the human female is contro- 

 versial. Nevertheless, softening of the cervix 

 following treatment with relaxin has been 

 reported (Eichner, Waltner, Goodman and 

 Post, 1956; Stone, Sedlis and Zuckerman, 

 1958) although McGaughey, Corey and 

 Thornton (1958) reported no effect on the 

 cervix following relaxin. 



