90 ON THE PLACENTAL STRUCTURES OF THE TENREC 



relative 1 to it which he has done, and to which, as entailing- yet 

 another error, we shall have to revert. 



In both the early and advanced embryo, the non-placental uterine 

 mucous membrane becomes continuous with the saucer-shaped 

 deciduous serotina on its convex aspect, about the eighth of an 

 inch within a line corresponding with the periphery of the after- 

 birth, or, in other words, along a line concentric with, but an 

 eighth of an inch within the thickened band of the late embryo. 

 The circular parapet by which the persistent and deciduous uterine 

 structures are connected is but a slight lamina, and gives way upon 

 very little traction. The blood vessels and cellular tissue within 

 its periphery serve to keep the after- birth in continuity with the 

 persistent non-deciduous serotina. Indeed, in the agouti the blood 

 vessels form the only bond of union, and the after-birth becomes 

 ' pedunculate,' at least if we may trust an observation put on record 

 by BischofF 2 as made by Dr. Franz Muller. On the other hand, 

 the guinea-pig's deciduous serotina is connected with the uterine 

 non-placental mucous surface by a series of tags or fimbriae, 

 developed at its periphery, as well as with the non-deciduous 

 serotina by an abundance of vessels. These peripheral tags are 

 most distinctly continuous with the uterine walls, and are injectible 

 from the uterine vessels, whence it is much to be wondered at that 

 Bischoff (1. c. p. 42) should have spoken of them as the remnants 

 of the perfect decidua reflexa of earlier days. These tags are to 

 be seen in a foetal rat, in Prep. 3467, Hunterian Museum, and 

 they are described as follows : { The folds or processes of the lining 

 membrane of the uterus which converge to be attached to the 

 maternal portion of the placenta, are here shown/ Their office 

 is described to be that of { supporters of the embryo, and con- 

 ductors of the vessels of the maternal placenta.' With this de- 

 scription my own of the homologous growths in the guinea-pig 

 will be seen to agree ; but I should be inclined to say that in the 

 preparation in question there is besides the system of radiating 

 peripheral tags, also the uterine circular parapet, usually found 

 alone in the rat, co-existing with them, though I have not been 

 able to satisfy myself of the co-existence of these two connecting 



1 Kolliker, I.e. pp. 160, 161, 172. 



2 ' Meerschweinchen-Ei,' p. 6; Muller, 'Wiener Zeitschrift,' 1851; Schmidt, 

 Jahrbucher,' bd. lxi. p. 329. 



