Anatomical Observations on the Lungs

breaks into the lungs, it requires a continuous path for easy and sudden entry and exit. For this reason, perhaps, that internal tunic of the trachea The windpipe., ending in sinuses and vesicles These 'vesicles' are what we now call alveoli, the tiny sacs where oxygen enters the blood. Malpighi was the first to describe them accurately., creates a mass of vesicles similar to a common sponge. This also seems to be indicated to me in a dried lung by the uniform substance, color, and brightness reflected equally from the cut end of the tracheal canal and from the attached small circles and ends. Indeed, the internal surface of the trachea is coated with a light moisture, which must necessarily be propagated in the same proportion into the small circles where air is finally received and expelled, so that they are not dried out by the heat of the passing blood (for the membranes are extremely thin and rare) and so that they can be dilated into a larger volume and immediately compressed—which would by no means happen in dried membranes, as is evident in diseased constitutions.

Here one thing presents itself for investigation: in a tiny outermost fragment of the lungs held up to the light, a certain wonderful network original: "rete". This is Malpighi's first observation of the capillary network, the "missing link" in William Harvey's theory of blood circulation. appears extended, by which you would say the individual vesicles emerging and swelling out are bound and tied together. This same thing is also observed, though obscurely, in a lung cut internally. Whether this network is a vessel, or something nervous extended to the vesicles, or whether they are the very membranous walls of the vesicles ending at the outermost investing membrane, is a doubt for me. However, because in the internal parts—either in particles flying off during drying or lightly scraped away with a knife—certain nervous offshoots of this network sometimes seem to remain, and in the outermost parts a certain brightness and a manner of substance proper to nerves seems to be observed, I would therefore not believe it absurd that it is a nervous ligament united and mixed with the walls of the vesicles, just as we see those cartilaginous semicircles propagated in the rough trachea original: "aspera trachea". A common historical term for the windpipe, referring to its ridged, cartilaginous texture.; and especially since it is probable, as I proposed above, that those vesicles are offshoots of the internal membrane of the trachea.

The division of the pulmonary mass is commonly taken from its shape and position; for it has two parts with the mediastinum The central partition in the chest cavity that separates the lungs. coming between them, which again in