522 Proceedings of the Royal Society 
after birth, leaving the foramen ovale soon partially covered by a 
valve. Even subsequent to the formation of the quadrilocular heart 
of the foetus, still the ductus venosus is the only outlet of venous 
blood sent to be oxidised and returned by the arteries to the aortic 
bulb for circulation. The foramen ovale (rationally explained) per- 
mits the free passing of the blood to and from the ventricles, and 
readily explains what Dr Churchhill could not — “ That the pulse de- 
tected by the stethescope, when applied to the maternal abdomen, 
indicated twice the rapidity detected at the cord in cases of pro- 
lapsus or turning.” The systole of the auricles preceding that 
of the ventricles may be detected by the ear; but being imme- 
diately followed by the stronger contraction of the ventricles tilting 
the apex against the sides of the chest, as in the adult, impresses 
the finger when applied to the cord wfith half the rapidity of the 
pulse indicated by the stethoscope. 
V. Towards the close of pregnancy a much greater change is 
being inaugurated preparatory to the inflation of the lung-cells. 
The very beautiful demonstration by Dr Tonge by a well-con- 
ducted series of experiments on the aortic bulb of the chick, in 
a paper communicated to the Royal Society last year by Pro- 
fessor Beale. 
Dr Tonge describes, towards the close of incubation, that there 
may be traced, extending from the upper left angle of the bulb, 
below the entrance of one of the left terminal branches of the aorta, 
the commencement of a fine film of its lining membrane descend- 
ing diagonally to the lower right corner (the right aorta and its ter- 
minal branches having disappeared). This division into two tubes 
he describes as being closed by three semilunar valves, preventing 
the flow of the arterial blood into the ventricles. 
While these changes are going on in the bulb, the right ventricle 
pushes a horn over the auriculo- ventricular septum and auricles, 
from the right margin of the heart upwards to the left side of the 
bulb, and passing behind it ramifies into right and left pulmonary 
trunks. The left ventricle, in like manner, pushes its horn behind 
the mitral valve, under the right auricle, and, rising over the upper 
part of the aortic bulb, carries off the innominata, carotid and sub- 
clavian arteries, as well as crushing off the last upper left terminal 
branch of the aorta (leaving a small portion, which quickly becomes 
