Galen's Commentaries on the Aphorisms of Hippocrates

...to encompass [all] fevers together, according to the ancient acceptance of the term. To this is added that it is better to permit nature to be free to attend to the concoction of the disease, while the disease remains at its peak, and not to distract her toward digesting recently consumed food; for this reason, when the disease is at its peak, one must use a very slender diet. This, therefore, being supposed, in other diseases that are to reach their peak later, it is not permitted to apply a very slender diet immediately from the beginning. For the man will die before the disease stands at its peak. In those

.viii.

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When the disease is at its peak, then a very slender diet must be used.

.ix.

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One must conjecture, however, whether the sick person may suffice to endure with the diet until the disease reaches its peak, and whether he might fail earlier and be unable to endure with the diet, or whether the disease might fail and grow dull before then.

diseases, however, where the peak of the disease is about to occur immediately—that is, in the first four days—in these we can use an extremely slender diet; and when the strengths even tolerate total fasting, it is permitted to provide only honey-water and a very little juice of barley water. Such indeed is the very slender diet. But that which is less slender than this, which he also called "fuller," is appropriate for those diseases which must reach their peak later, in which he commands one to depart from the slenderness of diet only as much as the disease recedes from the extremes—that is, from the highest peak. For when the peak is near, we shall provide a slightly fuller diet; when it is further away, more; and as much as we expect the highest peak of the disease to be later, by so much shall we change the form of the diet.

.viii.

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This discourse is likewise a certain part of the art that teaches how to apply a suitable diet, which is written separately by some following the words just said, but by others is annexed to the preceding aphorism in the manner in which it was written before. It teaches us, however it may be written, one and the same rule of diet prescribed by the ancient master: where the disease is at its peak, a very slender diet must be used, both because of the magnitude of the crisis and for the concoction of the disease; for nature ought not to be distracted toward another new concoction, when at that time she is powerfully free for the concoction of the harmful humors and is about to overcome them not much later. For so we have shown in the treatise On Crises. Now, however, the discourse is conducted only concerning those diseases in which we intend both the cure and the rule of diet; these indeed are those in which a decline follows after the peak. For in those whose highest peak is followed by death, we use that part of the art which he calls prognostics, foretelling what is to happen, lest the outcome of events be ascribed to our error. Let this, therefore, be one indication for you, taken from the stages of the disease for the rule of diet; the other indeed is from the strength of the sick person, which he teaches in the following aphorism.

.ix.

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Because in the previous aphorism he only commanded to deviate from that which is called an extremely slender diet to the extent that the disease is milder than its peak, now in this place he adds another consideration, so that we may know the quantity of the deviation precisely. This consideration is the very strength of the sick person, for whose sake we provide nourishment, and not for the sake of the disease. For when the strength is so robust that we hope it can endure the entire intermediate time until the highest peak of the disease with such a form of diet, then we shall have that precise quantity of deviation of which we spoke. But if it should be weaker, something must be added to the diet, and a fuller [diet]...