Volume 1

Microcosm of London / [Anon].

Date:
[1808-1811]
Catalogue details

Licence: Public Domain Mark

Credit: Microcosm of London / [Anon]. Source: Wellcome Collection.

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    and they supposed the veins to be the only channels for the blood. Galen discovered that the blood flowed both by the arteries and veins, but he was ignorant of its natural course. The pulmonary circulation was known to Severus and several other eminent men. Fabricius ab Aquapendente (who was the pre- ceptor of Harvey) has particularly described the valves of the veins, by which the blood is prevented flowing at their extremities. But even Harvey was unacquainted with the direct communication which subsists between the arteries and the veins: he thought the blood transuded through a spongy substance into the latter. This great discovery of Harvey’s paved the way to almost all the important improvements which have since been made in the science of medicine. Aselli, an Italian physician, discovered the lacteals, by which the chyle is carried through millions of tubes (whose perforation is too fine even for the microscope to discover), and deposited in the glands of the mesentery, where being attenuated by a thin diluting lymph, it is conveyed to the common re- ceptacle, and mounts by .a perpendicular tube called the thoracic duct (which was discovered by Pecquet in France), to be poured into the left subclavian vein, where mixing with the blood, it loses the name of chyle. From this vein it passes into the vena cava superior, and through the right auricle of the heart is forced into the right ventricle; from thence, by the astonishing mechanism of these parts, it is compelled into the great or pulmonary artery, which carries it to the lungs, and by its contracting power drives the blood into every part of that organ. It is in this amazing laboratory it imbibes oxygen from the air we breathe* and in consequence of which it assumes a more brilliant colour. It then enters the left auricle by the four pulmonary veins, and is thence protruded u 2
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