125 
Aufsätze. 
Nachdruck verboten. 
A theory of the structure of the placenta. 
By CHartes-Sepewick Minor. 
In a review of recent investigations upon the structure and de- 
velopment of the rabbit’s placenta, which was published in the Bio- 
logisches Centralblatt, Vol. X, p. 114, I briefly indicated the theory 
of placenta, which I had formed. Since the appearance of my article 
Duvar’s memoir on the rabbit’s placenta (Journal de |’ Anat. norm. et 
path., 1889, 1890) has been completed. Duvau instead of bringing 
what I can admit as a correct history of the foetal villi, has fallen 
into serious errors, of which two are especially important. These two 
are: 1° interpreting the hypertrophied endothelium of the maternal 
vessels as foetal ectoderm; 2° regarding the sections of the tissue 
separating the mesoderms of adjacent villi, as tubes, instead of as 
sections of partitions. The first error has lead Duvat to a false con- 
ception of the outgrowths of the foetal ectoderm, the second error has 
prevented his recognizing the true villi, for he interprets the sections 
of the fused ectodermal surfaces of adjacent villi as tubular outgrowths 
of the ectoderm. In speaking thus positively, I ought perhaps to say 
dogmatically, in regard to Duvar’s errors, I do not wish to neglect 
the recognition due to him, but only to state my own position clearly 
and briefly. I feel sure that my criticisms are justified by the facts, 
or I should not make them, but others, who share my own high re- 
spect for DuvAar’s work will naturally wait, before acceding to my 
views, until they have more than my bare affirmations to judge by. 
I have stated my position towards DuvAL, because acceptance of his 
results is incompatible with the theory here advanced. 
For the purposes of this article I have considered the placental 
mammals as divided into two main groups, the clawed forms, Ung uicu- 
lata, and the hoofed forms, Ungulata. The unguiculata have the 
true chorionic placenta, to which reference is principally made in the 
following paragraphs. The ungulate or allantoic placenta has not only 
a distinct type of organization but also probably a distinct evolutionary 
history from the chorionic placenta. 
