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DRS. A. CARTE AND A. MACALISTER ON THE 
the lungs were bounded anteriorly and posteriorly by the pulmonary plexuses formed 
by the pneumogastric and phrenic nerves. The divisions of the bronchi were traceable 
into the substance of the lung for a very considerable distance, retaining their cartilages 
to their seventh division, when the tubes measured about one line in diameter. Nothing 
remarkable was found in the minute anatomy of the lung ; its parenchyma was highly 
elastic, and contained a quantity of yellow fibrous tissue. 
Pericardium, and Heart. 
The pericardium was conical in shape, with its expanded base attached posteriorly to 
the central portion of the muscular and tendinous diaphragm ; it exhibited no pecu- 
liarities in its arrangement or in the sheaths accompanying the vessels that arose from 
the heart, which were similar to those of mammals in general. 
The crescentic fold described by Marshall, which corresponded to the obliterated 
left superior vena cava, was not perceptible ; this fold, we may observe, does not seem 
to bear in its development any relative proportion to the size of the animal in which it 
is found, as, for example, we have not seen it nearly so well developed in the horse as in 
the human subject. 
The heart in its external configuration displayed little worthy of special remark ; it 
was rather flatter than the hearts of most mammals, and had no white spot of Baillie ; 
its apex was rounded, and its auricular appendices were short and blunt ; the coronary 
arteries were large, forming a vascular collar round the circumference of the organ, and 
sent off branches which, as usual, marked the divisions between its cavities. 
The wall of the right auricle was about the fifth of an inch thick, and its endocardiac 
aspect exhibited very strong musculi pectinati ; the greater eustachian valve was but 
slightly marked, but the lesser fold was more distinct, and the superior cava had no pro- 
tecting valve. 
The foramen ovale was obliterated, but the annulus Vieussensii surrounding it was 
well defined, prominent, and muscular. The right auriculoventricular opening was 
guarded by the usual tricuspid valve, which was extremely strong and well marked. 
The wall of the right ventricle was about § of an inch thick, and its cavity was crossed 
by a strong trabecula, the moderator band of King, which was attached to its anterior 
and septal walls. The conus arteriosus was short and dilated, and, as usual, gave off the 
pulmonary artery. 
The left auricle was rather smaller than the right) its wall was also smoother and 
thinner, measuring only of an inch in thickness ; five pulmonary veins opened into 
it, two on the left and three on the right side. 
The wall of the left ventricle, at the base of the heart, measured If inch in thickness 
and f of an inch at its apex ; its muscular bundles were extremely powerful, and its 
mitral valve large and strong. 
The aortic and pulmonary valves displayed no novel anatomical points worthy of 
remark. 
