PLACENTAL STRUCTURES OF THE TENREC. 297 
that Bischoff, who has figured what is nothing else than this primitive chorion (fig. 59, 
Meerschweinchen-Ei), should have yet fallen into the error relative’ to it which he has 
done, and to which, as entailing yet another error, we shall have to revert. 
In both 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* as 
made by Dr. Franz Miller. On the other hand, the Guinea Pig’s deciduous serotina 
is, as shown in our figure 5, connected with the uterine non-placental mucous surface 
by a series of tags(p s") or fimbriz, 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 (/. c. p. 42) should have spoken of 
them as the remnants of the perfect decidua reflexa of earlier days. Our figure 6, and 
the description appended to it, will show where the rudiment of that structure is really 
to be sought for. ‘These tags are to be seen ina fcetal 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 conductors of the vessels of the maternal placenta.” With this description 
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, coexisting with them, though I have not been able to satisfy myself of the 
coexistence of these two connecting media in any placenta, as that of the Guinea Pig, 
which I have been able to manipulate. Neither have I ever been so fortunate as to 
find this system of tags in the common Rat (Mus decumanus) ; and but that the homo- 
logous structures, two only in number, which are to be seen in the Rabbit (Lepus cuni- 
culus), and are figured and described in Pl. L. figure 7, are far from being invariable in 
their appearance, I should suggest that the foetal Rat in question was of the Black Rat 
(Mus rattus) species. 
1 Kolliker, 2. c. pp. 160, 161, 172. 
2 ©Meerschweinchen-Ki,’ p. 6; Miiller, ‘Wiener Zeitschrift,’ 1851; Schmidt, ‘Jahrbiicher, Bd. Ixi. 
p. 329. 
