PLACENTAL STRUCTURES OF THE TENREC. 301 
decidua vera, which was supposed to be deciduous in the Human species and in no 
other, is occasionally not deciduous at all where its caducity has been laid such stress 
upon, whilst in the Chimpanzee the relations of the non-placental as of the placental 
deciduz seemed to me to be those more ordinarily described as met with in the 
Human subject. 
A third difference has been stated to exist between the Human and all other placentz, 
namely, that the foetal capillaries were in it, and in it alone, bathed in a sinus-system, 
not merely apposed to vessels of similar or somewhat similar calibre. This distinction 
was propounded by Weber in 1832, and indeed was known even earlier than that date’. 
The existence of this sinus-system was questioned by Eschricht*, as previously by Von 
Baer®, but without good reason. Since that time its existence has been nearly universally 
held to be distinctively anthropic*. Robin®, however, after saying “la disposition de 
veines en forme de sinus ne se voit pas que chez la Femme,” adds “‘ et peutétre chez ceux 
des Singes dont l’uterus a une paroi musculeuse épaisse et rigide non intestiniforme.” 
I must also confess that I am unable, in a section of the placenta of the Macacus nemes- 
trinus, to recognize any such apposition to the fcetal arborescent villi of maternal 
vessels, as contradistinguished from maternal sinuses, as the usually held views would 
demand. Though the injection thrown into the maternal vessels has penetrated down 
to the chorionic floor of the placenta, it does not seem, under the microscope, to have 
mapped out for itself those vascular trees which are so easily distinguishable in other 
placentz in the like position, and, in this placenta, in the foetal villi. It is right, 
however, to add that the Monkey-placenta which I have been describing was injected, 
skilfully and successfully it is true, but still a considerable number of years before it 
came into my hands for examination; so that possibly less weight may be assigned to 
the results of a microscopic inspection of the relation of its maternal and foetal blood- 
vascular systems than would have been due to a similar investigation of it in the 
recent state. I am not, however, myself inclined to think that the lapse of time has 
made any difference of consequence in the appearances in question. Approximations, 
on the other hand, to the sinus arrangement of maternal intraplacental vessels have 
been noticed by Eschricht (J. c. p. 24) as existing in the Cat ; and Kolliker (J. c. pp. 163, 
170) speaks of the ‘‘ colossal capillaries,” 3!" wide, of the Dog’s placenta, as forming, in 
contradistinction to the ordinary capillaries of the homologous parts in the Rabbit, the 
Ruminants, and the Pig, a transition towards the arrangement which, in the previous 
sentence, he characterizes as exclusively Human. 
It is well to put on record the fact that upon yet a fourth point of supposed 
difference between the Simious and the Human placenta considerable weight has been 
laid, which close examination has shown it would not bear. This point was the per- 
> Froriep, ‘ Notizen,’ p. 90, no. 996. 2 De Organis, p. 28. 
5 Gefiissverbindung, p. 25, 1828. * Hunt. Cat. 3583 ; Kolliker, J. c. p. 170. 
* Mém. Acad. Méd. Paris, 1861, p. 133. 
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