82 CARNEGIE INSTITUTION OF WASHINGTON. 



taneous rhythmic contractions of the smooth muscle of the genital tract and 

 that these variations bear a definite relation to the oestrous cycle and early 

 pregnancy. They discovered this variation in rhythm by suspending in 

 oxygenated Locke's solution strips of muscle from specimens representing 

 various stages of the cycle and recording their contractions by means of a 

 kymographion. From Mr. Keye's observations we find that during the time 

 the Graafian follicles are maturing, and for a short time after they rupture, 

 the rhythmic contractions of the smooth muscle of the uterus are, for the most 

 part, of relatively large amplitude and of long duration (1.5 to 2.5 minutes). 

 Superimposed upon these are minor waves of higher frequency, and as the 

 cycle advances from one oestrus, through the interval, to another (from the 

 third to the twelfth day of the cycle) the minor waves gradually replace the 

 major waves until about the fifteenth day, when the major waves begin again, 

 reaching their maximum with the enlargement of a new crop of Graafian 

 follicles. Pregnancy definitely alters the type of cyclic contractions. As 

 early as the sixth day of pregnancy Mr. Keye observed a marked diminution 

 in both types of waves, the minor type apparently entirely disappearing. 



The smooth muscle of the tube presents an alteration in rhythm that is still 

 more marked than that of the uterus. Mr. Seckinger finds that during the 

 period of oestrus, and while the ova are still in the tube, the tubal contractions 

 are characterized by their rapidity (13 to 15 per minute) and by undulating 

 variations in amplitude. As the ova reach the uterus, the tubal contractions 

 drop in frequency to 5 to 10 per minute and lose their undulating character, 

 and this inter-oestrous type continues until the nineteenth day, when the 

 oestrous type is resumed. Mr, Seckinger finds that the change from the 

 inter-cestrus to the oestrous type of contraction takes place at a definite time, 

 namely, when the new follicles have attained a diameter of 7 to 8 mm., and it 

 is a significant fact that it is just at this time that the cells of the theca interna 

 of the Graafian follicle undergo marked histological changes indicative of 

 secretory activity. Pregnancy does not appear to have any effect upon the 

 type of contraction of the tube, the contractions remaining identical with 

 those of the inter-oestrous period. Both Mr. Keye and Mr. Seckinger point 

 out the possibility that the variations in these muscular contractions may be 

 the active agency in the transportation of ova and early embryos to their final 

 position for implantation in the uterus. 



Permeability of the Placenta. 



In view of the considerable difference in the structure of the placental bar- 

 rier, as found in the cat and the rabbit. Dr. R. S. Cunningham has extended 

 his studies on placental permeability to the latter animal. He has been able 

 to demonstrate that in the rabbit both sodium ferrocyanide and iron ammo- 

 nium citrate pass from mother to fetus, though sodium ferrocyanide passes the 

 placental ectoderm somewhat more easily, being found in the fetal blood 

 before the citrate and being present in greater concentration. Since the 

 placental barrier in the rabbit is of a simpler type, one might well expect a 

 decreased amount of placental control. Nevertheless, some control over and 

 above the ordinary laws of osmosis and diffusion does exist, even in this 

 simple hemo-chorionic type. 



