434 Proceedings of Royal Society of Edinhurgh. [july 9, 
chiefly by traction of the retracting muscle on the lower uterine 
segment ; above the contraction ring the increase in area during the 
third stage happens after the pain, during the uterine diastole, and 
not being participated in by the comparatively bloodless placenta, 
leads to the necessary disproportion of separation. It is evident 
that this disproportion of separation has its necessary limits. 
Measurement of the trabeculae in the spongy layer, and a knowledge 
of the amount of elongation necessary to tear healthy trabeculae, 
should find an approximation to its value, but my work on this 
point is not as yet ready for publication. 
Literature. 
Hicks, J. B., Anatomy of the Human Placenta, Lond. Ohst. Jour., xiv., 1873. 
Turner, SirWn., Lectures on the Anatomy of the Placenta. Edinburgh, 
1876. Observations on the Structure of the Human Placenta, Jour, of 
Anat. andPhys., 1873. 
Waldeyer, Mediaiischnitt einer Hochschwangeren u.s.w. Bonn, 1886. 
Uber den Placentarkreislauf des Menschen, SitzungsbericTite der K. P. 
Akad. der Wissenschaften zu Berlin, vi., 1887. 
An important part of the proof advanced in the present paper 
depends on the existence of the intervillous circulation. This cir- 
culation is denied by Hicks, and strongly contended for by Turner. 
Waldeyer, in a recent communication, unhesitatingly supports the 
view that an intervillous circulation does exist. 
Explanation of Plates XVIII., XIX. 
Fig. 1. Section of the placenta attached to inverted third stage uterus (muscle 
not shown). The amnion is stripped off, and the villi so closely 
pressed together that we see no intervillous system. 
Fig. 2. Section of shed placenta. Amnion stripped off, and intervillous spaces 
obliterated. 
Fig. 3. Section of 4| months’ placenta attached to uterus, but muscle not 
drawn. Note that in this pregnant specimen the intervillous spaces 
are evident. 
Fig. 4. Section of 6 months’ placenta from parturient uterus ; villi injected. 
Note villi so closely pressed that specimen seems one mass of them. 
Fig. 5. Space of trabecular layer magnified, showing lining of columnar 
epithelium. 
Fig. 6. Section of 3rd stage uterus with placenta attached. The trabecular 
layer is well seen, as also the close appression of villi. 
All specimens drawn with | inch object-glass, and reduced by one half. Fig. 5 
magnified 300 diameters. 
PI. XIX. shows a vertical mesial secretion of a third stage uterus, with 
placenta separated in part by a retroplacental blood present. This specimen 
