Problemata Aristotelis

...is food to bodies, which, once possessed and encompassed, we travel with. But the air does not present itself as food. Furthermore, there are many and varied types of waters in themselves, but of air there are very few. Thus, this can also be a cause, since it happens that when we have traveled, we are indeed in almost the same heaven, but it happens that we are involved in varied waters. Wherefore, it has been rightly thought that the mutation of waters is grievous.

Why does the mutation of foods and waters occur as less grievous? Is it because we consume the most water? For there is much use of water in bread, in side-dishes, and in drink.

But why does the mutation of foods and waters become grievous? Is it because every mutation, even of season and age, is easy in movement? For the extremes of any kind can be moved easily. Just as principles and ends. Therefore, even foods that differ among themselves can corrupt each other. Especially since what had preceded it has either recently or not yet attached itself. To these things, just as varied food is grievous, for its digestion is turbulent and not equal, so it happens in those who have changed water, namely that they use food of varied drink. And that kind of food is stronger because it is dry, since it is the most part. And from the foods themselves, only as much as is diluted has the power of nourishing.

Why do mutations of waters cause many lice to be held in those in whom they can be held? Is it because the crudity of the humor, which that disturbance commits—which overflows from the varied use of water in frequent mutation—can create an abundance of humor, especially in a place more opportune for humor? But the brain is naturally moist; wherefore the head is most perpetually moist. A sign of this thing is that hair grows most especially on it, and the power of this place is apt for generating...