very unusual Formation of the human Heart. 351 
no bronchial veins. From there being neither bronchial arteries 
nor veins, it would appear that the pulmonary arteries and 
veins, in addition to their usual offices, performed those of the 
bronchial vessels. 
The liver was not divided on its upper surface by the sus- 
pensory ligament, but had a considerable cavity scooped, as it 
were, out of its substance $ which, in shape, was adapted to* 
and contained, the heart : it was also, in some other particulars, 
rather different from its natural shape, but not sufficiently so 
to require being minutely described. The rest of the infant 
was examined, but was not found to be dissimilar to any other. 
These circumstances are expressed by the accompanying fi- 
gures of the parts when dissected ; (Tab. XVIII.) in taking of 
which, much attention was paid to render them very accurate. 
It is a well ascertained fact, that the blood receives a florid 
hue from the influence of the air on it in the lungs ; and this 
change is supposed to be effected by the combination of a cer- 
tain quantity of oxygen gas with it. In passing from the ar- 
teries to the veins, in every part of the body except the lungs, 
it loses the florid hue, and becomes darker : the florid blood is 
that which is employed for the purposes of supporting life. In 
the natural circulation, it is well known, that the whole of the 
blood conveyed to, and circulating in, the pulmonary artery, is 
of a dark colour ; and the whole of it, when returned by the 
pulmonary veins, is florid. 
It is obvious, in the case which I have described, that there 
always must have been florid and dark-coloured blood mixed, 
and circulating in the arteries. It would seem also, upon the 
first reflection, that the quantity of dark-coloured blood would 
be the greatest, in the same proportion as the capacity of the 
