536 



Capt. J. Hammond. 



opposite the placenta. Since these pustules consist of giant cells (fig. 1) 

 (which are supposed to be detached trophoblast cells) surrounded by a mass 

 of decidual cells, it seems quite possible that the myometrial cells are foetal 

 cells which have wandered to the muscular coat. 



As the cells of the myometrial gland do not occur constantly in all 

 pregnant rabbits, so far as we have been able to investigate, we must conclude 

 that they cannot have the important functions which Ancel and Bouin 

 ascribe to them. 



The Maternal Placenta. 



Many investigators have attributed to the placenta the property of 

 causing milk secretion (Halban,* Baschf), and, although as a primary cause 

 of the growth changes of the mammary gland in the first half of pregnancy 

 it is shown to be unnecessary, yet it seemed quite possible that it might 

 be responsible for the glandular phase of the second half of pregnancy. 



Injection experiments with placental extracts were not tried, since there 

 is great difficulty in getting fresh extracts sterile, and the process of 

 boiling is open to the objection that the active principle may be thereby 

 destroyed. The maternal placenta was, however, caused to form in rabbits 

 by the use of the methods adopted by LoebJ when studying tissue growth in 

 the uterus of the guinea-pig. 



Pseudo-pregnant doe rabbits, obtained by coitus with a vasectomised buck, 

 were taken at about the 7th day (the time at which the ovum normally 

 becomes fixed in the uterine wall), and the uterus was stimulated, in some 

 cases by snipping out pieces of the wall from each horn, or in other cases by 

 slitting the uterus for the whole of its length and then cutting small pieces 

 away from the edges. 



The rabbits operated on in this way form decidual cells in the parts of 

 the uterus which have been stimulated by cutting or by contact with a 

 foreign body (figs. 2, 3, and 4). These masses of decidual cells are prac- 

 tically identical in appearance with those of the maternal placenta. 



In each case the duration of pseudo-pregnancy dates from the day on 

 which coitus took place with the vasectomised buck. 



The results of the experiments are given below. 



* Halban, ' Arch, fiir Gynaek.,' vol. 75 (1905). 



t Basch, ' Monatsch. f. Kinderheilk.,' vol. 8 (1909). 



% Loeb, ' Jour. Amer. Med. Assoc.,' vol. 50 (1908), and ' Arch. f. Entwick. der 

 Organ.,' vol. 32 (1911). 



