PLACENTAL STRUCTURES OF THE TENREC. 315 



serotina has been artificially displaced from its natural condition of appositioa 

 with the uterine wall's non-deciduous serotina. It is still connected with the 

 uterine tissues by blood-vessels (b v) and by tags or fimbriae, d s", which pass 

 from its periphery to become continuous with the uterine mucous membrane. 

 From its concave surface there is a downward growth, d s', which embraced 

 the upgrowth (pl', or " Kern" of preceding figure), and which ends in two pro- 

 cesses, one (d r) being the remnant of the decidua reflexa, and the other (g) 

 having been continuous with f in preceding figure, and connected the deci- 

 duous serotina with the placenta. The persistent non-deciduous serotina is a 

 very thin layer, not separable as a distinct stratum to the naked eye from the 

 circular muscular coat, c m ; but it contains uterine glands. A wide interval, 

 partly artificial, and containing many blood-vessels (bv), separates the circular 

 from the longitudinal muscular coat, lm. The mesometrium (m) is attached 

 to the convex border of the figure 



Fig. 6. Decidua serotina, with remnant of reflexa, from aborted ovum of Guinea Pig 

 {Cavia aperea), viewed from its placental aspect. It was found loose, and with 

 nothing in connexion with it, in the uterine cavity of the individual whence 

 the preparations for the two previous figures were taken. Tags or fimbriae, 

 D s", by which it was attached to the uterine mucous membrane, proceed from 

 its periphery. Two of these tags are prolonged inwards on its placental 

 aspect to join the opposite poles of an inner raised circular cup, the decidua 

 reflexa (dr). Within and at the bottom of this is a concentrically corrugated 

 area of mucous membrane, which was thus thrown into folds for the reception 

 of the placental upgrowth (pl') of the ovum which was in connexion with it. 

 The vessels which passed to the placenta made their way to it mainly by the 

 depression in the centre of this area, c. (See Bischoff", Meerschweinchen-Ei, 

 figs. 54, 55, 57.) 



Fig. 7. After-birth of Rabbit {Lepus cuniculus), showing the prolongations of the decidua 

 serotina at either extremity of the structure, and their continuity with the 

 uterine mucous membrane (u m). The placenta is obscurely seen to be made 

 up of several (two or more) lobes, which are clamped together by a centrally 

 constricted decidua serotina (d s), the constriction corresponding to the in- 

 terval between the main divisions of the placenta. The decidua serotina has 

 its long axis at right angles to that of the uterine cornu, to the mesometrial 

 border of which it is, in this as in every other Rodent, attached. From 

 either end a process is very usually, as in this figure, prolonged beyond the 

 placental area to become continuous with the uterine mucous membrane on 

 the free half of the tube, portions of which in this connexion are drawn at 

 u M in this figure. These two processes represent the much more numerous 

 ones (d s") of the Guinea Pig's decidua serotina. Just fringing the lateral 



VOL. V. PART IV. 2 T 



