Anatomical Observations on the Lungs

so great is the branching of these small vessels as they emerge from the vein and artery that the regular order of the vessels is no longer preserved. Instead, a network appears, formed from the extensions of both vessels. This network not only occupies the whole area but extends to the walls and is attached to the outgoing vessel, as I was able to observe more fully, though with more difficulty, in the oblong lung of a tortoise, which is likewise membranous and transparent. From this it was made clear to the senses that the blood flows out divided through twisted vessels and is not poured out into open spaces Malpighi is refuting the older theory that blood simply pooled into the tissues like water in a sponge; he proves it remains contained within vessels., but is always driven through tubules and dispersed by the manifold bending of the vessels.

Nor is it a new habit of Nature to join the extreme mouths of vessels together, since she does the same in the intestines and other parts; indeed, what will seem more wonderful, she connects the upper ends of the veins with the lower ones by a remarkable anastomosisa cross-connection between adjacent channels, tubes, or fibers, as the most learned FalloppiusGabriele Falloppio (1523–1562), a seminal Italian anatomist excellently observed.

In order that you may more easily obtain these proposed results and follow them with your own sight, you should tie a thread around the place where the lung of a dissected frog is joined to the heart while the lung is emerging and swollen, nourished everywhere by plenty of blood. For once dried, it will preserve the vessels swollen with blood. You will then see these best if, exposed against the horizontal sun, you examine them with a flea microscopean early, simple single-lens microscope used to view small insects of a single lens. Or you can use another method for seeing these things: place the lung on a glass plate illuminated from below by the light of a lamp through a tube; to this, you will bring a microscope of two lenses, and thus the vessels spread out like rings will be revealed to you. With the same arrangement of instruments and light, you will observe the motion of blood through the aforementioned vessels, and you will be able to devise other ways yourself through different levels of light that escape description by the pen.

Regarding the motion of blood, one thing presents itself as worthy of your speculation: for when the auriclethe upper chamber of the heart, now called the atrium and the heart are tied, and thus the motion and impulse that could be derived from the heart into the attached vessels are removed, the blood still moves through the veins toward the heart, so that it distends the vessels by its own effort and the flowing abundance. This continues for several hours; in the end, however, especially if it is exposed to the sun's rays, it does not...