432 Proceedings of Royal Society of Eclinhurgli. [july 9 , 
The intervillous spaces, to our knowledge of which Sir William 
Turner has contributed so much, are also empty and the villi closely 
pressed together. This is an anatomical fact, as I have found them 
empty in all the third stage uteri examined, and also in the shed 
placenta. This is not to be wondered at when we remember the great 
thickening that has taken place in the wall of the third stage uterus, 
and the practical obliteration of the vessels there, during a pain. 
The emptiness of the intervillous spaces in the shed placenta, and 
close apposition of the villi, is clear evidence of the entire absence 
of blood in them during the third stage of labour. 
If the uterine be palpated during the third stage, it will be noted 
to harden and diminish in bulk markedly, and then to increase in 
bulk and become softer. During the hardening, the internal uterine 
surface diminishes greatly, the contraction ring barely admitting the 
finger, and the uterine wall thickens : during relaxation, the internal 
uterine area increases so that the hand passed in can be even moved 
about freely, and the contraction ring expands so as to allow the 
hand to pass. The condition of the uterine wall is not known 
exactly, but I believe it is thinner. Unfortunately, we do not 
know how the relaxing muscle increases the internal uterine surface 
in area, but as a matter of fact it does, and this diastole is probably 
active. One thinks of the relaxing uterine muscle as anything but 
active, but the term “ relaxation,” like so much of our terminology, 
is misleading. We know also, both by clinical and sectional 
evidence, that the lower part of the placenta often separates first. 
The mechanism of the separation seems to me therefore to be as 
follows : — When the child is born the placental area may diminish 
to 4 inches x 4 inches, as shown in a specimen in my possession. 
No separation takes place then, because there is no disproportion 
between the area of the uterine muscle to which the placenta is 
attached and the placenta itself. However much the area diminishes, 
the placenta cannot separate, because the disproportion necessary 
cannot take place. V/’hen the uterus contracts to the amount it 
does after the child is born, the placenta fills the uterine cavity, 
and any further diminution in uterine bulk never leads to a 
disproportion between placenta and the area of the uterine muscle to 
Avhich it is attached, but the two are always equivalent. 
After the pain has died off, the uterus relaxes, and as a matter of 
