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Whether urine is a simple or mixed body.

One asks further whether urine is a simple or mixed body.

1. It seems that it is mixed. This is because any part of a mixed body is itself mixed. But urine is derived from the nutriment, which is a mixed body, and therefore, etc.

2. Moreover, in book four of On Meteorology the Philosopher says that nothing simple putrefies or coagulates. But urine putrefies and thickens when it is changed and corrupted. Therefore, it is a mixed body.

To the contrary, every mixed body can nourish. But according to the physicians, urine cannot nourish. Now if this is true, then it is not derived from the nutriment; therefore, etc.

To this, one should respond that one should consider two things with respect to urine. One is that it is a moisture and that it trickles out of the members, and the other is that this [moisture] is resolved from parts of the food and mixed together with urine. But I say that according to the first reason it can be a simple body, but according to the second reason it is a mixed body. By means of this distinction I have refuted a certain physician of Cologne, who was accustomed to say that urine is absolutely a simple body.

1. And from this, then, to the arguments. To the first, one must say that something can be derived from a mixed body in two ways: either by a division of quantity, and in this way any given part of a mixed body is mixed; or by resolution, as happens when a mixture is resolved into its elements, and in this way it should not be necessarily true that a part of a mixed body be mixed. But urine can be derived from the nutriment by resolution and separation, and then it should not be necessarily true that it is a mixed body.

2. To the second argument one must respond that if urine thickens, this does not happen by itself, but happens because of the admixture of food and of an incorporated heat and spirit, which thicken or render deadly and cannot render it as clear as it was before.

On the urine of brute beasts.

Next, one asks why the urine of brute beasts is thicker than that of humans.

Second, why the wolf and the dog raise their leg or their hind foot when they are urinating.

Third, why dogs cannot see before a set time, for example, before the ninth or the fourteenth day.

To the first, one should respond that the more powerful the digestive power is, the more subtle and clear the urine is. Now, however, according to Avicenna the digestive power in brute beasts is not as tempered as it is in the human, because God gave humans the noblest complexion that could be found. This is why, etc. And because brute beasts eat coarse things, like things born of the earth, and chew them by ruminating, but the human eats more subtle things and has an especially tempered heat, and his other natural operations [are also tempered], a human's urine is therefore thinner than that of another animal.

To the second, one should say that the dog and the wolf are melancholic animals and a great deal of bile [cholera], which is pungent and biting, is mixed into their urine, and for this reason it damages the nerve-filled places in the bladder through which it passes. And because elevating the foot opens the pores and enlarges the passages through which the urine is emitted, for this reason, etc. And this is why they all urinate against something elevated, like a rock or something else, because in this way the earth receives the urine more quickly and quickly makes a rivulet visible to the dog's gaze, and this is why the dog believes it emits the urine more quickly and with less damage, and for this reason, etc.

Moreover, it is quite remarkable that after dogs and wolves have passed excrement,[1] they scratch the ground with their feet and cover it up. And this is why dogs often suffer colic from constipation, because they are gluttonous animals and swallow food without chewing it, and this swells the intestines. Therefore, because they suffer cramps when defecating, they tear at the ground as if they are angry and cast forth their excrement as if it were something poisonous and harmful. An indication of this is that when they have had a mild, soft bowel movement they do not do this, and if they do this, it is out of habit or they want to clean the anus. Thus according to Galen a dog's excrement is useful as an enema for every type of colic.[2] And this is clearly shown in our book On Animals.[3]

To the third, one should respond that at birth a dog has a narrowing in its nostrils and an abundance of moisture in its head. Now, nostrils act just like an overflow drain for the brain, and for this reason, because the brain and the head cannot be purged adequately through the nostrils, owing to the abundance of the material, the moisture flows to the optic nerve through which the visual spirit flows to the eyes, and this superfluous moisture renders the nerves poorly suited for motion, as can be seen in paralytics.[4] And this is why, when the optic nerve is softened, the eye cannot see; but as time passes, the natural heat is fortified and consumes these humors and expands the nasal openings, and, as a consequence, the optic nerve begins to harden and is rendered better suited for motion or for the visual spirits, and then the whelp begins to see.

This is a summary of the opinions found in the book On Animals.

  • [1] Lit., "have cleaned themselves," mundaverunt.
  • [2] The editor of QDA was unable to identify the appropriate passage in Galen, but suggests instead Avic., Can. med. 2.2.614,
  • [3] For some medicinal uses for canine feces, see A., DA,, 90 (SZ 2: 1464, 1502).
  • [4] For the medicinal, "drying" properties of beaver musk and leopard flesh, useful for paralytics suffering from this superfluous moisture, see A., DA,, 109 (SZ 2: 1468-69, 1514-15).
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