Home Philosophy The fathers of the church
One inquires about hair. And first, one inquires whether hair is generated from skin.
1. It seems not. For where the same cause is present, so too is the same effect. If, then, skin were the cause for the generation of hair, then all animals that have skin would have hair. But the conclusion is false, as is evident in birds and in fish, and therefore, etc.
2. In addition, the hard cannot be connected to the soft. But the first part of hair is hard and earthy, but what is inside the skin is soft. Therefore, they cannot be connected.
The Philosopher says the opposite.
Second, one inquires whether hair is nourished.
3. It seems so. Growth presupposes nutrition. But hairs grow. Therefore, they are also nourished.
4. In addition, that which is maintained with the arrival of nutriment, and fails when it is lacking, is nourished. But hair is like this. Therefore, etc.
To the contrary. Everything that is nourished or that has grown through nourishment is nourished throughout and grows in every direction. But hair is not like this. Therefore, etc.
Third, one inquires into the cause of the diversity in hair.
5. And it seems that hair ought not to be diverse. For whatever has the same matter and the same effect is not diversified. But hair is like this. For hair is generated from the vapor and humor in the skin and by the heat pushing it out.
6. In addition, hair is generated from the work of the third digestive power, which is evident from the fact that hair can be enervated in every part. But the third digestive power proceeds by whitening. Therefore, all hair will be uniform in color and, by the same argument, uniform in other respects.
The opposite is apparent to the senses.
To the first, one must reply that hair is generated in the skin. For when the nutriment is dispatched to individual members, it is dispatched to the skin. But there is often a weak digestive power in the skin, owing to its distance from the principle of digestion. Therefore, there are often fumes and earthy humors in the skin, and when these are dried out and expelled through the skin's pores, hair is generated. And this is why in all animals except the human, hair bears witness to the skin, that if it is white, then the hair is white, and if it is black, then the hair is black. But skin is finer in the human than in other animals. Therefore, human hair cannot be made hard, and the hair's matter cannot be made continuous on a person's skin; rather, the matter is concentrated under the skin, and this is why hair is not diversified in a human according to the nature of the skin, but rather according to the diversity of the nature of the humors under the skin.
1. On to the arguments. To the first, one must reply that only animals that generate have hair, because ones like this are warmer than the others. Therefore, they have more matter suited to hair and, likewise, to producing it. This matter is thicker in birds and fish, and this is why it is converted into scales and feathers, but it is thinner in other animals owing to the dominance of heat and blood, and this is why it suits the generation of hair better.
2. To the second argument one must reply that when a hair exits from the skin its matter is dried out by heat and then it is constricted by cold. And this matter is viscous and sticky and can be continued into a long hair. Therefore, insofar as something like this is concerned, the hard is not connected with the soft until the soft is hardened.
To the second question one must reply that something is nourished or grows in two ways. It can grow by a power that is present inside it, and this is how flesh and bone are nourished and growby the nutritive or augmentative power. Or something can be nourished or grow in another way, by adding something to it, and this is how fire is said to be maintained and to growby adding wood to it. Hair is not nourished in the first way, since it does not have a nutritive power within itself, nor does it grow in this way, since it then would grow in every direction. It is nourished and it grows in the second way, however, but to be nourished or to grow in this way is nothing other than to be generated, because, when the hair grows, the first part, which was present first, does not grow, but does acquire something new.
3, 4. With this a solution to the arguments is clear.
To the third question one must reply that differences in the matter and in the skin are the causes of diversity in the hair. Nevertheless, differences in the matter and the skin proceed from an agent. When the skin is thick and has wide pores and there is a lot of thick matter, then thick hair is generated. When, however, the skin is fine and the pores are narrow, then fine hair is generated. When the matter for the hair is abundant and very oily, then long hair is generated. And this is why hair on a person's head is longer than the other hair, because the skin on the head is thicker than the skin on other parts, and a viscous humor abounds in the head owing to its nearness to the brain, and this is why the hair is lengthened, and the hair is short for the contrary reason. If the hair's matter has been dried out a great deal, then the hair is curly and twisted. For, owing to the matter's dryness, the hair is hard, and, owing to the heat, it turns back almost to its place of origin. According to physicians the bending and twisted nature of the pores causes this. And an indication of this is that hair is curly in hot regions, as among Ethiopians and Indians, but in cold and moist regions the hair is smooth. If, however, the hair's matter is very dried out and the expelling heat is absent, then hair loss occurs. And this is why those who enjoy sexual intercourse too frequently go bald quickly, since coition dries out and cools the body, and, owing to this, old men go bald more than young men, because old men are cold and dry. Therefore, the ages [of man] resemble the times of the year. Because, just as in a hot and moist season, spring, for example, leaves grow on the trees, and feathers grow on birdswhich is why they particularly sing then, owing to the very great expansion of their lungs. Now these lungs contract in other seasons, and this is why they do not sing then but are sadand during a cold and dry season, like winter or the period close to it, like autumn, these things fall off (namely, tree leaves), and the feathers on birds decrease somewhat. In much the same way do these things occur in humans according to their different ages, with the difference that the seasons turn in a cyclical mannerthis is why the leaves, after they fall off, can grow and return in a cyclical fashion and after their regret they fall off againbut the ages of man do not return, and this is why animals like these cannot naturally restore their hair.
Again, hair color varies according to diversity of this humor. For when the humor is undigested and is rather watery, or when it is putrefied by means of an alien heat, the hair grows white and gray. This is why a person goes gray on the temples before he does so on other parts of the head, because there is so much humor in the front portion of the head that it cannot be easily corrupted. On the rear portion of the head it is so modest that it does not increase the heat but rather is quickly digested, and on the side of the head it is in-between these two. If, however, this humor begins to burn, then reddish hair is generated, and if is completely burned, then black hair is generated. Therefore, it is clear from this that differences occur in the hair according to differences in the skin and the humor.
5. On to the arguments. To the first, one must reply that the matter and the efficient cause are not related uniformly, because the matter is sometimes thick and sometimes thin; it can be fragile, viscous, putrid, and burned, and so too for the others. Likewise, the efficient cause can be a strong heat and can be overcome by weakness, etc.
6. To the second argument one must reply that although the third digestion proceeds by whitening, nevertheless at the end it proceeds by reddening, by burning, and by blackening. Or one can say that hair does not receive its color from the digestive power, but, rather, generally receives it from an external power such as an external heat. And this is why, etc.
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