AND THOSE OF CERTAIN OTHER MAMMALIA. 95 



erroneous ; but what we have already said is sufficient as to this 

 envelope. I should add that Virchow * has shown that the 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 rela- 

 tions of the non-placental as of the placental deciduae 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 placentae, 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 of somewhat similar calibre. This distinc- 

 tion was propounded by Weber in 1832, and indeed was known 

 even earlier than that date 2 . The existence of this sinus-system was 

 questioned by Eschricht 3 , as previously by Von Baer 4 , but with- 

 out good reason. Since that time its existence has been nearly 

 universally held to be distinctively anthropic 5 . Robin 6 , however, 

 after saying — 



* La disposition de veines en forme de sinus ne se voit pas que chez la Femme/ 

 adds, ' et peutetre chez ceux des Singes dont l'uterus a une paroi musculeuse epaisse 

 et rigide non intestiniforme.' 



I must also confess that I am unable, in a section of the placenta 

 of the Macacus nemestrinus, to recognise any such apposition to the 

 foetal 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 placentae 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 de- 

 scribing 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 



1 Virchow, 'Gesamm. Abhandlungen,' p. 782, 1856, cit. Dr. Matthews Duncan, 

 • Edin. Med. Journ.' Dec. 1857. 2 Froriep, ' Notizen,' p. 90, no. 996. 



3 * De Organis,' p. 28. 4 ' Gefassverbindung,' p. 25, 1828. 



5 Hunt. Cat. 3583 ; Kblliker, I.e. p. 170. 



6 ' Me*m. Acad. MeM Paris,' 1861, p. 133. 



