MAMMALIA. 715 



this subject* cannot be too highly appreciated. In the gravid 

 uterus of a Kangaroo, examined by this indefatigable labourer in 

 the cause of science, a fetus was met with that had apparently 

 arrived very nearly at the term of its intra-uterine existence ; and 

 the following is a summary of its anatomy at this period. 



The ovum (Jig- 330, c) was lodged in one of the uterine cavi- 

 ties, and the fetus was about an inch and four lines in length. The 

 walls of the gravid uterus were obviously dilated, and its parietes 

 varied in thickness from one to two lines, being in the unimpreg- 

 nated state about half a line ; but this increase was not in the mus- 

 cular coat, but in the lining membrane, which was thrown into irre- 

 gular folds and wrinkles. There was, however, not the slightest 

 trace of any vascular connection between the uterus and the ovum, 

 neither placenta nor villi, nor any determination of vessels to a 

 given point on either of the opposed surfaces of the chorion or 

 uterus : on the contrary, the external membrane of the ovum (cho- 

 rion) exhibited not the slightest trace of vascularity, even under 

 the microscope, and seemed in every respect to resemble the mem- 

 brana putaminis that lines the egg-shell. 



(841.) The body of the fetus itself was immediately enclosed 

 in a transparent membrane Fig. 330. 



(/;), the amnios. 



(842.) Between the 

 chorion (a) and the am- 

 nios (b) was an extensive 

 vascular membrane (c, d, 

 d, c, e) ; its figure seemed 

 to have been that of a 

 cone, of which the apex 

 was at the umbilicus of 

 the fetus. 



Three vessels could be 

 distinguished diverging 

 from the umbilical cord, 

 and ramifying over it. 

 Two of these trunks con- 

 tained coagulated blood ; 

 while the third was smaller, empty, and evidently the arterial 

 trunk. No trace of any other membrane could be seen extending 



* On the Generation of Marsupial animals, with a description of the impregnated 

 uterus of the Kangaroo, by Richard Owen, Esq. Phil. Trans. 1834. 



