Why the human lungs are more solid and are not divided into lobes.

Next one asks why the human lungs are more solid and are not divided into lobes as in the flyers. And it seems contradictory, because the heat is greater in the human heart than in that of another animal. Therefore, as a consequence, the human needs better ventilation in the lungs than do the others.

One must say that the heat is weak and dispersed in the flyers because they are ventilated a good bit by means of their feathers and plumes and through their pores. And this is why it is necessary that thinner spirits come to their hearts, because thick spirits would immediately extinguish the heart's heat. And this is the reason that there are many lobes in their lungs, so that the spirit that is drawn there will be better purified and rendered thinner before it is dispatched to the heart. But there is more heat in the human heart, and for this reason it can sustain cruder spirits, and because of this its lungs are not divided because an air that is rendered thin and pure is not sufficient to temper the heart, and the same is true for many of the brute beasts, like the cow, etc.

Why the kidneys and the eyes and ears are divided into pairs.

Why the right kidney is higher and larger than the left.

Further one asks why the kidneys and the eyes and ears are divided into pairs, but the other organs are not.

Second, one asks why the right kidney is higher and larger than the left.

To the first, one must reply that the kidneys in the human and in animals exist for the sake of the complete digestion of the watery fluid emitted by the liver. For the liver is a watery and very moist member, and the wateriness in the liver is mixed in with blood. Thus this wateriness is dispatched along two veins to the two kidneys, so that pure wateriness may be separated out from the blood. And this is why, in those with weak kidneys, the urine looks like water used to wash raw meat, because the kidneys cannot entirely purify it from the blood. The kidneys are located near to the vertebrae of the back. Thus, if they were joined together as one member, that member would be burdened by its size and would bring harm upon the other members, and this is why nature doubled them with one on one side of the vertebrae and the other on the other. And in the same manner nature made two eyes and two ears and two hands and two feet, so that, if one should happen to lose one of them, the remaining one could perform its task. This is not so for the other members.

To the second, one must reply that fat is caused by poorly digested moisture. Thus colder people, because they have a poorer digestion, are fatter than warmer people, as pigs are compared to other warm animals. In the same way, because the heat consumes and resolves moisture, as one can see in emaciated, choleric people and in many others owing to their lack of moisture. But the heart infuses its power on the right side. Thus there is naturally more heat on the right side than on the left, and, as a result, there is more heat in the right kidney. And for

this reason, because it is the trait of something warm to be located above and to consume moisture, this is why the right kidney is above and is larger, and the left is just the opposite, etc.

Why the exterior members are divided into pairs, while the interior members are not.

Why the eye and the ear are divided into pairs, but not the tongue, except in serpents.

Next one asks why the exterior members, like the eye and ear, are divided into pairs, while the interior members, like the heart and the liver, are not.

Second one asks why the eye and the ear are divided into pairs, but not the tongue, except in serpents.

To the first, one must reply that the interior members have the basis of a principle with respect to the exterior members, and a principle exists in one way, whereas things from a principle exist in several ways, and this is why the interior members are not paired as much as the exterior ones, because a principle ought to be simple and one.

To the second, one must reply that the tongue is fitted for two operations of nature, namely, for taste and for speech. But speech occurs through a mediating motion, and one motion impedes another motion which is not ordered to the same end. But among motions that are ordered to the same end, one assists the other, as Galen says in the first book of On Critical Days [De Crisi].[1] Thus if there were two tongues and both spoke at the same time, then the voice of one would impede the voice of the other, just as the voice of one person impedes the voice of another. And this is why animals that make sounds do not have two instruments for calling or giving voice. Serpents, however, live on very cold nourishment, for they live off earth, and this is why they need an instrument that is better disposed for perceiving flavors, because the earth is not very flavorful. And this is why nature gave two tongues to these, so that they might better distinguish the flavors of their food. Thus serpents appear

to have a divided tongue at least on the end, even though these are not two tongues absolutely. Nevertheless, we have seen in *** a serpent having two tongues which could even be petted in a lap.[2] Nevertheless, some of the peripatetics say that they have one tongue in place of a stinger, where the venom is, and especially in the teeth, so that they taste with one and they puncture or fight with the other.

  • [1] Not in the place indicated (see Kuhn 9: 550ff.).
  • [2] None of the MSS offers a reasonable reading for the lacuna in the text. It would appear to be a place name, and one reading, that of P, in regno, translates as "in the kingdom" and puts one in mind of Frederick II's love of animals. Likewise, quem etiam in gremio fovi potest post, itself of dubious meaning, is of decidedly odd Latinity and may also be corrupt. See A., Super Is. 40:11, ed. Ferdinand Siepmann (1952), 412, ll. 68, 82.
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