Whether the bones are necessary.
One asks about the bones. First, one asks whether the bones are necessary.
1. It seems not. For the entire body and every single part of the body is ordered toward sensation, but bones are insensible, according to the Philosopher in the third book of On the Soul. Therefore, bones are unnecessary.
2. Besides, every part of the body is capable of receiving aliment and the vital spirit. But the bones, since they are solid, are not capable of receiving aliment or spirit, because they are opaque bodies. Therefore, etc.
The opposite is apparent to the senses. For nature would not always produce bones in an animal unless they were necessary, and therefore, etc.
One must reply that the bones are necessary for three reasons: one is that they are the foundation for the entire body. For everything that flows requires something solid, which is its boundary, so that it will have a determinate shape, and this is why flesh and fat and like things have the bones as their foundation.
Another reason is that they will be the armor and defenses for the principal parts. Now the skull is the protector for the brain, and the pectoral bone is the protector of the heart, and so on for the others. For just as a wise king, when he builds a city or a fortress, not only fashions them out of things from which a fortress or city is constructed, but actually even makes defenses to protect what he has built, so too naturewise in that very wisdom through which it was born to obey its Creator and which is the overseer and the artisan of all thingsfashions bones in the animal as a defense for the body, etc.
The third reason is that they are capable of supporting the body. For if there were no bones in the feet and in the thighs and legs, they would not support the body.
1. On to the arguments. To the first, one must reply that some parts of the body, like the organs, are ordered to sense, and others are ordered to be capable of sustaining and supporting the organs, and this is why, although the bones are insensible, they nevertheless are not superfluous, because they support the body.
2. To the second argument one must reply that, although the bones are solid when compared to the flesh and similar parts, bones are nevertheless somewhat porous, and as a result are capable of receiving the nutrimental moisture, as much as is sufficient for them, and this is why, etc. In this way a solution is evident.
Whether the bones have sensation.
One asks next, based on this, whether bones have sensation.
1. It seems so. Sensation is present in anything that has a power that can sense what is agreeable or injurious to it. But a power of this sort is in bones, and therefore, etc.
2. In addition, pain is a sensation of something that is contrary, according to the second book of On the Soul as well as according to Galen. But sometimes the bones experience pain. Therefore, there is sensation in them.
3. Moreover, the same argument applies to both bones and teeth since, according to Avicenna, the teeth share the nature of bones. But we experience sensation through the teeth, and therefore also through the bones.
The Philosopher says the opposite in the third book of On the Soul as well as in this book.
One must reply that bones do not experience sensation in their own right [ per se]. And the reason for this is that sense is receptive of sensible species apart from matter, and this is why it is required that there exist a mean proportion of sensibles in sensibility. For which reason "plants do not have sensation," according to the Philosopher in the third book of On the Soul, because earthiness abounds in them and they do not receive [sensible] species apart from matter but are rather altered by matter. But bones are likened to plants by the Philosopher in the book On Plants, and they do not exist in a medium conducive to tangibles. They therefore receive [sensible] species in their own right [ per se] in a material fashion, and this is why they do not have sensation. And an indication of this is that if the web surrounding the bones is removed, and they are struck with a painful blow, they do not feel it. Yet because the bones are often joined to a nerve and fleshy parts, this is why it appears to us that sensation occurs in bones, because it occurs through the sensation of the other parts. Thus they have sensation by virtue of the nerve-filled parts and the pannicular-membranes attached to them, but not in their own right [per se].
1. On to the arguments. To the first, one must reply that the first act of actual sensation exists in the bones, because, just as life is diffused through all the parts of the body, so too is sensation. But the second act of sensation only exists in an organic part attendant upon the sense itself. This is why, owing to the first act of actual sense and of life, it has a power of discriminating between what is suitable and of repelling what is harmful, but that sensation nevertheless does not exist there. And beyond this one can say that a power receptive to what is suitable and that repels what is harmful exists in a plant, and that sensation nevertheless does not exist there either.
2. To the second argument one must reply that bones do not feel pain per se but only per accidens as a result of the pain in other parts, just as blood does not exist in the brain in its own right [ per se] and yet nevertheless, as a result of a lesion in other, adjoining parts, swelling and a flux of blood can occur in parts like these which do not have blood in their own right [ per se].
3. To the third argument one must reply that teeth adhere firmly to fleshy parts with certain nerves in between them [medi-antibus], and this is why the teeth know painbecause the pain in the nerve travels to the teeth, but this occurs per accidens, specifically, by virtue of the nerves. And because dry things greatly retain or incorporate impressions received, pain in the teeth is therefore very strong, because they are dry and hard. And this is why the pain imprinted on them lasts a long time.
-  No clear analogue can be found in this Ps. Aristotelian work, although the reader may want to examine De plantis 1.3 (313a18-22; Meyer, 1841).
-  "In a medium conducive to tangibles": a troubled phrase, in medio tangibilium. Recall that touch consists in a mean proportion of sensible or tangible qualities. See QDA 1.17 (92, 39-40).