1888.] Dr Berry Hart on Separation of the Placenta. 431 
diminution in bulk of the placenta, owing to the comparative 
emptiness of the intervillous spaces. But why does the placenta 
diminish in area with the uterus during a pain ? Why does it in- 
crease in area again as the pain dies off, and Why is it not separated 
until after the child is born ? 
The reason seems to me to be that, owing to the foetal blood 
pressure, the placenta is pressed against the uterine wall sufficiently 
to make it practically act in unison with it, so far as increase and 
diminution of area are concerned, and the increase in the general- 
contents-pressure of the uterus during a pain will also tend in the 
same way, and both will prevent any separation. As the pain 
dies off, the foetal blood is at once pumped vigorously into the 
expanding villi, and causes the placenta to increase in area, as the 
corresponding part of the uterine wall to which it is attached does. 
The maternal blood pours into the intervillous spaces, and is also 
a factor in the expansion as the pain dies off. The reason why 
the placenta is not separated (unless praevia) during the first and 
second stages of labour, seems to me quite evident. Separation is 
brought about, as we shall see, by a tearing of the trabecular 
layer. This layer lies between placenta and uterine wall, and can 
only be torn when the placental site and the placenta at the plane 
of the spongy layer are unequal. So long as the placenta responds 
exactly, by diminution and expansion of its area, to the diminution 
and expansion (brought about by the pain) in area of the muscular 
surface of the uterus to which it is attached, there can be no tension 
on the trabeculae, and no tear of them. 
When the child’s head is born, no inspiration take place, as the 
placenta is not separated. When a pain comes, the face of the 
child becomes congested, the congestion passing off as the pain dies 
away. The reason of the congestion is the comparative emptying of 
the intervillous spaces and the slowing of the foetal heart, both 
tending to produce a certain amount of asphyxia. The compression 
of the villi is physically like a vasomotor construction in an adult, 
and causes the slowing of the heart. 
When the child is born, it cries vigorously, and aspirates the 
blood from the villi. If allowed to remain attached for some time 
(say an hour) it can remove the blood from the villi almost 
completely. But not only are the villi emptied of the foetal blood. 
VOL. XV. 29/11/88 2 E 
