On the complexion of the heart.
It follows now to speak about the nature of the teeth," etc. In this thirteenth book one should first inquire about the heart, because earlier there was an investigation into teeth and nails. And first one inquires into the complexion of the heart.
1. And it seems that the heart is hot and moist. For the one generating and the one generated are alike. But the heart is the principle of the blood's generation, and the blood is hot and moist. Therefore, the heart is hot and moist.
2. Moreover, like is nourished by one like itself. But the heart is nourished by the thinner blood, and therefore, etc.
3. Moreover, life depends on the hot and moist. But the heart is the principle of life. Therefore, etc.
To the contrary. According to the Philosopher, the heart is opposite to the brain, both in its disposition and its location. But the brain is cold and moist. Therefore, the heart, by its opposition, is hot and dry. The proof is here in the Topics: "When you have two contraries, if some property is in the one, the contrary property will be in the other."
To this, one must reply that the heart can be considered in two ways: either materially or formally. If materially, then the heart's complexion is melancholic because the heart is very hard and compact, and this is why it nourishes most poorly, according to Isaac [Israeli] in his Diets [Dietae]. If it is considered formally, then the heart is choleric with a hot and dry complexion. It is clear that it is hot because the natural heat and spirits flourish in the heart. It is also clear that it is dry, because heat cannot be preserved long in a moist material. But heat is preserved in the heart for life's duration. And this is why it is necessary for it to be in a dry material.
Moreover, the heart is a principle of motion and is not susceptible to injury, according to the Philosopher in the first book. Therefore, it is necessary for it to have the power to resist noxious things, and the moist cannot do this as the dry does. This is why, etc.
Therefore, briefly one can say that the heart has a melancholic complexion as a result of its mixture, whereas insofar as it is the principle of the generation of blood and the spirits it has a choleric complexion. Thus, when properly speaking about the heart, just as now one inquires about the heart, it is hot and dry; nevertheless, it becomes moist by virtue of the blood contained in it, which is delegated to it from the liver.
1. On to the arguments. To the first argument one must reply that what is generated resembles the one generating in acts of generation taken univocally. But the heart is not related in this way to the blood.
2. To the second argument one must reply that although the nutriment is similar in the end, in the beginning it is dissimilar.
3. To the third argument one must reply that life depends on the hot and the moist, whose principle is in the heart, because the radical moisture and natural heat take their origin from the heart. Therefore, life depends on these just as it does on proximate principles. But it does not necessarily follow from this that the heart is hot and moist formally, but it suffices for it to be hot and moist effectively.
Whether an animal that has a large heart is fearful.
One inquires further whether an animal that has a large heart is fearful, or whether a large heart is a sign of fearfulness, as is said in the text.
1. And it seems not. Males are generally larger than females, but males are bolder than females. Therefore, a large heart corresponds more to boldness than to fearfulness.
2. In addition, boldness is caused by the natural heat and by the strength of the power and spirits. But these can be contained better in a large heart than a small one, and therefore, etc.
The Philosopher says the opposite.
One must reply that a large heart may arise from two causes: either from an abundance of matter alone or from the intensity or strength of the active power [virtus agens]. The first type of largeness is not a good sign, because power is much weaker in a dispersed matter than in a compacted matter, just as the Philosopher says, that "fire warms a large house less than a small one." The second type of largeness is a good sign, however, because if the heart is large and the heat and spirit are proportionate to it, then a large heart can do more than a small one. Therefore, if the heart is large and the other parts are proportionate to it, this is a sign of boldness. If, however, it is large and the power of these others is not proportionate to it, then this is a sign of fearfulness. And in this case a small heart is better than a large one. And for this reason an animal with a small heart may be bolder than an animal with a larger heart, just as the lion is bolder than the horse, and the dog is bolder than the cow.
1. On to the arguments. To the first argument one must reply that males are bolder than females not only because they surpass the females with respect to the size of their material members but also with respect to the strength of their power and of the other spirits, etc.
2. To the second argument one must reply that if the natural heat corresponds proportionately to the large size of the heart, a large heart is better than a small one. But the Philosopher is not speaking about this; rather, he speaks by way of comparing the same heat to a large and a small heart. And therefore the effect [of the heat] has greater influence on a small heart than on a large one.