Brain anatomy

As for the anatomy of the human brain, it is divided into the substance of the membranes, the medulla and the cavities in it filled with pneum. And the nerves are like branches coming out of the brain, and are not particles of substance inherent in the brain. The entire brain is divided in half longitudinally. This division extends to the membranes, medulla and ventricles, for the pairing of parts already has a certain usefulness, although this pairing is more clearly visible in the anterior ventricle alone. Brain matter is created cold and wet. The brain is cold so that it is not inflamed by the strong movements of the nerves reaching it, the impressions of the senses and the movements of the pneuma that take place during the changes produced by imagination, thinking and remembering, and also in order to moderate the very hot pneuma that penetrates the brain from the heart through two vessels ascending to the brain. The brain is created moist so that it does not dry out movement and so that it has the proper shape. It is also designed to be soft and greasy. Fatness is necessary so that the nerves growing from the brain are sticky, and regarding softness, Galen says: The reason for this is so that the brain has a good shape and the ability to change with the imagination - after all, softness perceives changes more easily.

So says Galen. I will say that the brain is created soft in order to be fat and to well nourish the nerves that gradually thicken towards the ends, for the nerves are nourished by both the brain and the spinal cord. In addition, a hard substance does not provide nutrition to something hard in the same way that something soft does. The brain was created soft also so that what grows from it would be pliable, since some nerves growing from the brain must become denser at the ends due to the usefulness of the nerves, which we will mention later. And since the growing nerve must gradually become denser and its density is the density of something pliable, then it is necessary that the place from which it grows be pliable and fatty in substance - and what is sticky and fatty is necessarily soft. The brain is also soft so that the pneuma contained in it, which needs rapid movement, can receive help from its moisture, and, finally, in order to be light due to its looseness, for hard organs are heavier than soft, moist and loose ones. . However, the substance of the brain at the same time is unequal in terms of softness and hardness, since the front part is softer and the back part is harder. These two parts are separated, forming a fold, by a hard shell that reaches the anterior lobe of the brain, which we will mention below.

The anterior lobe of the brain is soft only because most of the sensory nerves, and in particular those that serve

for sight, smell and hearing, grow from there. After all, feelings are like sentinels for the body, and it is better for the sentinel to be facing the front side. And the motor nerves for the most part grow from the posterior lobe of the brain, from where the spinal cord grows, which is the ambassador of the brain and its deputy in the spinal cord canal. Since strong nerves and motor nerves, which need excess hardness, should come out of this part of the brain, while the sensitive nerves do not need hardness and softness is more appropriate for them, then the place of their exit is created more hard. The membrane forms a fold in the brain in order to serve as a partition, and some say - to save the soft from contact with the hard, for the substance into which the membrane is embedded is, on the one hand, very hard, and on the other, very soft. This shell also has other benefits: the vessels descending to the brain need support and something to connect them; this fold is designated as their support. At the end of this bend, in the rear part, there is a wine press, that is, a place where blood is poured into an empty space like a reservoir. Ducts branch out from it, through which the blood disperses, then becoming like the substance of the brain. Then the vessels absorb blood through their mouths and collect it into two large veins, as we mentioned in the anatomy of these veins. This fold is also useful because ligaments of the membrane grow from it, tightly adjacent to the brain against the suture of the part of the skull adjacent to it. In the front part of the brain, two mastoid processes begin, with the help of which the sense of smell is carried out. They are slightly inferior to the brain in softness, but do not reach the hardness of the nerves.

The entire brain is surrounded by two membranes. One of them is soft and adjacent to the brain, the other is thick and adjacent to the skull bone. They are created as partitions between the brain and bone, so that brain matter does not come into contact with the bone and so that damage to the bone does not spread to the brain. Such contact occurs only in the case of an increase in the substance of the brain or during its expansion, which occurs after compression. Sometimes the brain rises to the bone of the skull under some special circumstances, such as when shouting loudly; It is for this kind of utility that these two partitions between the brain and the bone of the skull are intended, intermediate in softness and hardness. Two of them were created so that the thing suitable for direct contact with the bone would not be the same thing that is suitable for direct contact with the brain. On the contrary, a difference has been created between them: the membrane close to the brain is thin, and the one close to the bone is thick, and both together are, as it were, a single protection for the brain. This membrane, being a protection, also serves as a ligament for the vessels in the brain, resting and beating. Like the membrane of an embryo, it maintains the position of the vessels that are woven into it unchanged; it also supports those vessels that enter the substance of the brain in many tortuous places and reach the ventricles of the brain; at the back of the brain the membrane breaks off abruptly, since the hardness of the brain in this place makes it unnecessary. And the thick shell does not stick either to the brain or to the thin shell so as to lie on it in all places; on the contrary, it is separated from it and they are connected only by vessels passing through the thick shell into the thin one. The thick shell is attached to the skull by means of membranous ligaments that extend from the thick shell and attach it to the sutures so that it does not put too much of a burden on the brain. These ligaments rise from the sutures to the outside of the skull and are located there, intertwined into a membrane covering the skull; thus, the thick shell is firmly attached to the skull as well.

There are three ventricles located longitudinally in the brain. Although each ventricle is divided transversely in two, only in the anterior lobe is there a clear division into two parts located on the right and left. This part of the brain contributes to the inhalation of air and the expulsion of excess by sneezing, as well as the distribution of much of the sensory pneuma and the action of the representative forces belonging to the faculties of internal perception. As for the posterior ventricle, it is also large, for it fills the cavity of a large part of the organ and is the beginning of something large, that is, the spinal cord; Most of the propulsion pneuma is distributed from it. and in this place the actions of the remembering power are carried out. But still it is smaller than the anterior ventricle and even each of the two lobes of the anterior ventricle; at the same time, it gradually decreases towards the spinal cord and gradually thickens to hardness. And the middle ventricle is like a passage from the anterior lobe to the posterior lobe of the brain and a kind of corridor arranged between them. Therefore it is large and long, for it leads from one vast space to another vast space. Through it, the anterior pneuma connects with the posterior pneuma and memorized images penetrate. The beginning of this middle ventricle is covered with a roof, the inner side of which is rounded, like a vault, and is called the fornix. This vault should serve as a passage and, moreover, due to its rounded shape, it is less susceptible to damage and is strong enough to support the folded shell resting on it. Here the two anterior ventricles of the brain are connected, so that they are visible from the posterior ventricle through the said passage; this place is called the junction of the two ventricles and the passage itself is also a ventricle. Since this is the passage leading from the place where images arise to the place where they are stored in memory, this, as you already know, is the best place for thinking and imagination. Proof that these ventricles are the focus of the forces from which such actions emanate is their disorder due to damage to the ventricles; When each lobe of the brain is damaged, their action stops or is disrupted. A thin membrane penetrates inside and covers the ventricles of the brain right up to the space near the fornix, and what is located behind the fornix does not need to be covered with a membrane, due to its hardness.

As for the convolutions present in the ventricles of the brain, they exist so that there is a passage for the mental pneuma into the substance of the brain, as well as into its ventricles, for the ventricles are not always expanded and open, and the pneuma is not always so small that the ventricles alone could contain it all. Moreover, the transition of the mental pneuma from the nature inherent in the heart to the nature inherent in the brain occurs only through transformation, as a result of which it acquires the nature of the brain. Having reached the brain, pneuma first of all enters its first cavity and undergoes transformation there, then it penetrates into the middle ventricle, where it is further transformed, after which its transformation is completed in the middle ventricle. Perfect transformation occurs only when the particles of the substance being transformed combine and mix with the particles of the transforming substance and penetrate into them, as happens with a nutrient in the liver, which we will talk about later. However, the number of individual convolutions in the anterior part of the brain is greater than their number in the posterior part, for the ratio of convolutions to convolutions approximately corresponds to the ratio of part to part, and the reason why the posterior ventricle is smaller than the anterior one also exists in the convolutions.

Between the middle and posterior ventricles and below them there is a place from where two large vessels rise to the brain, which we talked about above, and are divided into branches from which the chemise-shaped membrane in the lower part of the brain is woven. These branches rest on a body of glandular material, which fills the spaces between them and supports them, as happens in all vascular branches, for the voids formed between them must also be filled with glandular meat. The outline of this gland corresponds to the outline of the branches described and the form of the branching mentioned above. Just as the named branches and branches are at first narrow, and then diverge in breadth, because this is required by the expansion of the network of vessels, the gland also takes the form of a pine cone: with its apex it adjoins the beginning of the branch from above and goes to the end of it to the place where the hanging branches end. ramifications. There is tissue similar to that of the embryo, and branches are established in it.

The lobe of the brain containing this middle ventricle, and especially the parts of it located above, are worm-shaped and furrowed with wrinkles running longitudinally and connected to one another, so that the ventricle can stretch and contract like a worm; from the inside, its upper part is covered with a membrane lining the brain to the border with the posterior ventricle. The worm is attached to two oblong appendages of the brain, similar to the thighs, which approach until they touch or move away from each other, forming a gap. Attachment is achieved through ligaments called tendons; they are needed to prevent the worm from moving away from the appendages. When the worm stretches and its width decreases, it compresses these appendages until they connect, and the passage into the ventricle closes; when it contracts and shortens, becoming wider, the appendages separate from each other and diverge, and the passage opens. The part of the worm adjacent to the posterior lobe of the brain, like a thing that goes into something, is fitted to its container. And its front part is wider than the back part, according to the shape that the brain allows. The two appendages mentioned are called grapes. There are absolutely no wrinkles on them; on the contrary, they are created smooth in order to close the passage and close more tightly, and so that their response to the movement caused by the movement of another thing is more like the response of something unified.

To expel excess from the brain, there are two channels: one in the anterior ventricle, at the common border between it and the subsequent lobe, and the other in the middle ventricle. The posterior ventricle does not have a separate duct, and this is because it is located on the edge and, moreover, is small compared to the anterior one and does not allow the formation of a passage within it. For it and for the middle ventricle, one spinal cord is sufficient, and especially since this duct serves as the exit point for the spinal cord, and part of the excess is absorbed there and expelled from this side. Both of these ducts, starting from the two ventricles and penetrating into the brain itself, go obliquely to meet at a single deep passage, the beginning of which is at the thin shell, and the end, that is, the lower part, at the hard shell. This duct gradually narrows and is like a funnel, it begins with a wide, rounded part and ends with a narrow part. Therefore, it is called a funnel and is also called a tub. Having penetrated the hard shell, it encounters a duct passing through the gland, like a ball, compressed from two opposite sides: above and below; this gland lies between the hard shell and the palatine canal. Next, he finds ducts there located in the spongy lobe of the ethmoid bone, in the upper part of the palate.