As for Galen’s netlike plexus, I do not need to pass on a lot of misinformation about it here, as I am quite sure that I have examined the whole system of the cerebral vessels. There is no occasion for making things up, since we are certain that Galen was deluded by his dissection of ox brains and described the cerebral vessels, not of a human but of oxen.

At this point, however, I have no intention whatever of criticizing the false teachings of Galen, who is easily first among the professors of dissection, for I certainly do not wish to start off by gaining a reputation for impiety toward him, the author of all good things, or by seeming insubordinate to his authority. For I am well aware how upset the practitioners (unlike the followers of Aristotle) invariably become nowadays, when they discover in the course of a single dissection that Galen has departed on two hundred or more occasions from the true description of the harmony, function, and action of the human parts, and how grimly they examine the dissected portions as they strive with all the zeal at their command to defend him. Yet even they, drawn by their love of truth, are gradually calming down and placing more faith in their own not ineffective eyes and reason than in Galen’s writings.

For, however much we may clench our teeth in anger, we cannot but confess, in opposition to Galen’s teaching but in conformity with the might of Aristotle’s opinion, that the size of the orifice of the hollow vein at the right chamber of the heart is greater than that of the body of the hollow vein, no matter where you measure the latter. Then the following chapter will show the falsity of Galen’s view that the hollow vein is largest at the point where it joins the hump of the liver.

Galen never inspected a human uterus.

How many things have been accepted on the word of Galen.

However much the pits may be apparent, yet none, as far as can be comprehended by the senses, passes through the septum of the heart from the right ventricle into the left. I have not seen even the most obscure passages by which the septum of the ventricles is pervious, although they are mentioned by professors of anatomy since they are convinced that blood is carried from the right ventricle into the left. As a result—as I shall declare more openly elsewhere—I am in no little doubt regarding the function of the heart in this part.

I am not accustomed to saying anything with certainty after only one or two observations.

I strive that in public dissection the students do as much as possible so that if even the least trained of them must dissect a cadaver before a group of spectators, he will be able to perform it accurately with his own hands; and by comparing their studies one with another they will properly understand, this part of medicine.

It was above all in the period after the devastating incursions of the Goths that all branches of knowledge which previously had flourished gloriously and been practiced in the proper manner, began to deteriorate. This happened first of all in Italy where the most fashionable physicians, spurning surgery as did the Romans of old, assigned to their servants such surgical work as their patients seemed to require and merely exercised a supervision over them in the manner of architects.

Men today who have had an irreproachable training in the art are seen to abstain from the use of the hand as from the plague, and for this very reason, lest they should be slandered by the masters of the profession as barbers… . For it is indeed above all things the wide prevalence of this hateful error that prevents us even in our age from taking up the healing art as a whole, makes us confine ourselves merely to the treatment of internal complaints, and, if I may utter the blunt truth once for all, causes us, to the great detriment of mankind, to study to be healers only in a very limited degree.

Nature, the parent of all things, designed the human backbone to be like a keel or foundation. It is because we have a backbone that we can walk upright and stand erect. But this was not the only purpose for which Nature provided it; here, as elsewhere, she displayed great skill in turning the construction of a single member to a variety of different uses.
It Provides a Path for the Spinal Marrow, Yet is Flexible.
Firstly, she bored a hole through the posterior region of the bodies of all the vertebrae, thus fashioning a suitable pathway for the spinal marrow which would descend through them.
Secondly, she did not make the backbone out of one single bone with no joints. Such a unified construction would have afforded greater stability and a safer seat for the spinal marrow since, not having joints, the column could not have suffered dislocations, displacements, or distortions. If the Creator of the world had paid such attention to resistance to injury and had subordinated the value and importance of all other aims in the fabric of parts of the body to this one, he would certainly have made a single backbone with no joints, as when someone constructing an animal of wood or stone forms the backbone of one single and continuous component. Even if man were destined only to bend and straighten his back, it would not have been appropriate to construct the whole from one single bone. And in fact, since it was necessary that man, by virtue of his backbone, be able to perform a great variety of movements, it was better that it be constructed from many bones, even though as a result of this it was rendered more liable to injury.

Of all the constituents of the human body, bone is the hardest, the driest, the earthiest, and the coldest; and, excepting only the teeth, it is devoid of sensation. God, the great Creator of all things, formed its substance to this specification with good reason, intending it to be like a foundation for the whole body; for in the fabric of the human body bones perform the same function as do walls and beams in houses, poles in tents, and keels and ribs in boats.
Bones Differentiated by Function
Some bones, by reason of their strength, form as it were props for the body; these include the tibia, the femur, the spinal vertebrae, and most of the bony framework. Others are like bastions, defense walls, and ramparts, affording natural protection to other parts; examples are the skull, the spines and transverse processes of the vertebrae, the breast bone, the ribs. Others stand in front of the joints between certain bones, to ensure that the joint does not move too loosely or bend to too acute an angle. This is the function of the tiny bones, likened by the professors of anatomy to the size of a sesame seed, which are attached to the second internode of the thumb, the first internode of the other four fingers and the first internodes of the five toes. The teeth, on the other hand, serve specifically to cut, crush, pound and grind our food, and similarly the two ossicles in the organ of hearing perform a specifically auditory function.

The source and origin of the nerves is the brain and spinal marrow, and hence some nerves originate from the brain and some from the spinal marrow. Some … experts set down the heart as the origin of the nerves and some the hard membrane that envelops the brain; none of them, however, thought it was the liver or any other viscus of that kind … Aristotle in particular, and quite a few others, thought that the nerves took origin from the heart.

When I undertake the dissection of a human cadaver I pass a stout rope tied like a noose beneath the lower jaw and through the two zygomas up to the top of the head, either more toward the forehead or more toward the occiput according as I want the cadaver to hang with its head up or down. The longer end of the noose I run through a pulley fixed to a beam in the room so that I may raise or lower the cadaver as it hangs there or may turn it round in any direction to suit my purpose; and should I so wish I can allow it to recline at an angle upon a table, since a table can easily be placed underneath the pulley. This is how the cadaver was suspended for drawing all the muscle tables... though while that one was being drawn the rope was passed around the occiput so as to show the muscles in the neck. If the lower jaw has been removed in the course of dissection, or the zygomas have been broken, the hollows for the temporal muscles will nonetheless hold the noose sufficiently firmly. You must take care not to put the noose around the neck, unless some of the muscles connected to the occipital bone have already been cut away. It is best to suspend the cadaver like this because a human body lying on a table is very difficult to turn over on to its chest or its back.

… our “Physick” and “Anatomy” have embraced such infinite varieties of being, have laid open such new worlds in time and space, have grappled, not unsuccessfully, with such complex problems, that the eyes of Vesalius and of Harvey might be dazzled by the sight of the tree that has grown out of their grain of mustard seed.