On the Female Organs and Placentation of the Racoon. 279 



one and a quarter inches in greatest breadth where it lay in contact 

 with the dorsal surface of the foetus, while opposite the belly of 

 the latter the placenta did not exceed half an inch in breadth. 

 The placenta had been detached from the uterus, a circumstance 

 which I cannot sufficiently regret, as I was thereby prevented from 

 observing by means of injection the exact relation which existed be- 

 tween the maternal and foetal portions of the placenta. Although 

 detached from the uterine wall, it was evident that no change had 

 taken place in the position of the placenta with reference to either the 

 uterus or foetus, and consequently the somewhat exceptional position 

 of the latter in utero can in no way be attributed to this circumstance. 

 The placenta formed a complete ring, but at the centre of its widest 

 part, i.e., opposite the back of the foetus, there was a spot similar to 

 that figured by Daubenton* in the placenta of Martes domestica, and 

 described by Bischoff in that of Lutra vulgaris^ Mustela foina and 

 Mustela martes,^ where the substance of the placenta was deficient. 

 This deficiency involved the entire thickness of the placenta, so that 

 a probe could be passed from the uterine to the chorionic surface of 

 the organ without injury to its substance. The absence of placental 

 substance at this spot is of much interest in view of the observations 

 of Bischoff: upon the corresponding arrangement in Lutra, to which I 

 shall afterwards refer. To the foetal surface of this portion of the 

 placenta the amnion was closely adherent. The entire uterine surface 

 of the .placenta, with the exception of a band along either margin, 

 which measured one-eighth of an inch in breadth, presented a very 

 regularly papillated appearance. The marginal bands were perfectly 

 smooth and of a lighter colour than the rest of the organ. Subsequent 

 examination showed that this smoothness was due to the presence of 

 a layer of decidua (reflexa) which concealed the subjacent papillae. 



Chorion. — I have already remarked that the foetal membranes had 

 been ruptured where they lay in contact with the posterior extremity 

 of the embryo. In consequence of this I experienced some difficulty 

 in the determination of their exact arrangement. With the view of 

 completing this with greater exactitude, I removed the entire ovum 

 from the uterus, and having carefully extracted the foetus by dividing 

 the umbilical cord, as well as the narrowest part of the placenta, I 

 placed the latter, together with the foetal membranes, in a vessel con- 

 taining spirit. By floating out the membranes in this way I obtained 

 the view represented in fig. 2. From this drawing it will be observed 

 that a membrane which is continuous with each margin of the placenta 

 is prolonged outwards from the latter, so as to form a barrel-shaped 

 envelope in the interior of which the foetus was contained. This 



* Buffon's " Histoire Naturelle," vol. vii, PI. XX. 

 t " Sitzungsber. Akad. Wissensch," Miinchen, 11 Marz, 1865. 

 X Ibid., 13 Mai, 1865. 

 VOL. XXXII. U 



