94 PROFESSOR TURNER ON THE PLACENTATION OF THE SLOTHS. 
The placenta of the Carnivora is at once distinguished from that of the 
Sloth by several striking characters:—By its zonary form ; by the presence, 
not only in the unimpregnated uterus, but in the non-placental area of the 
gravid uterine mucosa, and in the maternal part of the fully developed placenta 
of utricular glands ; by the intra-placental maternal vessels retaining the form 
of a capillary net work ;* by the brevity of the umbilical cord; and by the 
persistence both of the umbilical vesicle and allantois. 
In the Insectivora, Rodents, and Cheiroptera again, the placenta, though with 
some slight modifications in its shape, forms a single “discoid” organ which in 
some cases at least shows a subdivision into lobes ; the allantois and umbilical 
vesicle, the latter of which is of large size in many genera, persist as dis- 
tinct sacs throughout intra-uterine life, and no evidence has been advanced 
that the intra-placental maternal vessels are dilated into sinuses. REICHERT has 
shownt that in these orders a decidua reflexa, more or less complete, exists. 
The condition of the mucous membrane, as regards the utricular glands, exhibits 
some variations in different genera. Lrypic has observed them in the mole ;{ 
ERCOLANI in the hedge-hog ;§ REicHErT in the guinea pig ;|| ERcoLani in Mus 
musculus ;1 in which animal he says they are few in number, simple, and slightly 
sinuous. In the rabbit there is some difference of opinion as to the nature of 
the deep depressions which exist in its uterine mucosa, for though REICHERT com- 
pares the windings and folds of that membrane to the appearance exhibited by the 
convolutions of the brain, and speaks (MULLER’s Archiv, 1848, p. 80) of the invo- 
lutions of the mucous membrane as short and wide, yet he evidently regarded 
them as essentially the same as the tubular utricular glands in the pig, guinea 
pig, bitch, &c.** Erconani again states that the rabbit, instead of possessing 
utricular glands, has numerous very short glandular follicles, which are only 
inflexions of the epithelial layer,and represent in this animal the uterine mucosa. 
These follicles, he says (p. 146), develope largely during pregnancy, are trans- 
formed into a glandular organ, and appear destined to replace, during pregnancy, 
the utricular glands which are wanting in these animals. I have had the oppor- 
tunity of examining sections through not only the non-gravid uterine mucosa 
* T am aware that Escuricar, in his important memoir (De Organis, &e., p. 24),speaks of the vessels 
in the feline placenta as exhibiting dilatations, and that KouiiKer (‘‘ Entwicklungs Geschichte,” p. 163), 
states that in the bitch the maternal blood-vessels are very strongly developed, and appear as very 
thin-walled capillaries }” in breadth, but I have not seen in the placenta of this animal vessels at all 
comparable with the sinuses in the sloth. 
+ Beitrage zr Entwicklungs Geschichte des Meerschweinchens in Abhand. der Konig. Akad. der 
Wissensch. zu Berlin, 1861. 
t Lehrbuch der Histologie, p. 517. 1867. 
§ Sur les Glandes Utriculaires de l Uterus, p. 10. French translation. Algiers, 1869. 
|| Op. cit. plates i. i. p. 117, and Mtuuur’s Archiv. p. 80. 1848. 
{| Sulla le Glandole Otricolari dell Utero. Mem. dell’ Acad. delle Se. di Bologna, p. 26. 1873. 
** The naked-eye appearance of the folds of the mucous membrane of the rabbit’s uterus has been 
carefully described and tigured by M. H. Hotxarp, in Annales des Sciences Naturelles, p. 223. 1863. 
