Abū Bakr Muhammad ibn Zakarīyū Al-rāzī, A Treatise on the Small-Pox and Measles (c. 910)

Despite the rise of independent Islamic states in the ninth and tenth centuries, the Islamic world remained interconnected through language, commerce, and increasingly through learning. The Abbasid caliphs had set this process into motion by establishing research libraries and institutes for the study and translation of the classics of Persia, India, and Greece. With the decline of the Abbasid dynasty, local rulers stepped in as patrons and supporters of science, math, medicine, and the art Muslim philosopher and physician Abū Bakr Muhammad ibn Zakarīyū Al-rāzī (c. 865–c. 925) was an influential product and propagator of the diffusion of Islamic learning and intellectual achievement. Born in the Iranian city of Rayy, Al-rāzī studied medicine in Baghdad and eventually became the director of a large hospital there. He wrote numerous philosophical and medical works, including A Treatise on the Small-Pox and Measles. In the excerpt that follows, Al-rāzī sets forth his views on the cause of the disease, which he asserts neither ancient nor contemporary scholars had sufficiently addressed. He takes particular aim at Galen, a second-century Greek physician whose writings had been translated into Arabic. Although Al-rāzī’s treatise was not the first work on the topic, it had a wide and enduring impact in the Muslim world and beyond. In the eighteenth century, it was translated twice into Latin at a time when Lady Mary Wortley Montagu brought public attention to the Turkish practice of inoculation against smallpox.

From Abū Bakr Muhammad ibn Zakarīyū Al-rāzī, A Treatise on the Small-Pox and Measles (London: Sydenham Society, 1848), 24–25, 27–31.

In the name of God, the Compassionate, the Merciful.

. . . It happened on a certain night at a meeting in the house of a nobleman, of great goodness and excellence, and very anxious for the explanation and facilitating of useful sciences for the good of mankind, that, mention having been made of the Small-Pox, I then spoke what came into my mind on that subject. Whereupon our host (may God favor men by prolonging the remainder of his life,) wished me to compose a suitable, solid, and complete discourse on this disease, because there has not appeared up to this present time either among the ancients or the moderns an accurate and satisfactory account of it. And therefore I composed this discourse, hoping to receive my reward from the Almighty and Glorious God, and awaiting His good pleasure.

Of the Causes of the Small-Pox; How It Comes to Pass That Hardly Any One Escapes the Disease; and the Sum of What Galen Says Concerning It

As to any physician who says that the excellent Galen has made no mention of the Small-Pox, and was entirely ignorant of this disease, surely he must be one of those who have either never read his works at all, or who have passed over them very cursorily.

If, however, any one says that Galen has not mentioned any peculiar and satisfactory mode of treatment for this disease, nor any complete cause, he is certainly correct. . . . As for my own part, I have most carefully inquired of those who use both the Syriac and Greek languages, and have asked them about this matter; but there was not one of them who could add anything. . . . This I was much surprised at, and also how it was that Galen passed over this disease which occurs so frequently and requires such careful treatment, when he is so eager in finding out the causes and treatment of other maladies.

As to the moderns, although they have certainly made some mention of the treatment of the Small-Pox, (but without much accuracy and distinctness,) yet there is not one of them who has mentioned the cause of the existence of the disease, and how it comes to pass that hardly any one escapes it, or who has disposed the modes of treatment in their right places. And for this reason we hope that the reward of that man who encouraged us to compose this treatise, and also our own, will be doubled, since we have mentioned whatever is necessary for the treatment of this disease, and have arranged and carefully disposed every thing in its right place, by God’s permission.

We will now begin therefore by mentioning the efficient cause of this distemper, and why hardly any one escapes it; and then we will treat of the other things that relate to it, section by section: and we will (with God’s assistance,) speak on every one of these points with what we consider to be sufficient copiousness.

I say then that every man, from the time of his birth till he arrives at old age, is continually tending to dryness; and for this reason the blood of children and infants is much moister than the blood of young men, and still more so than that of old men. And besides this it is much hotter; as Galen testifies in his Commentary on the “Aphorisms,” in which he says that “the heat of children is greater in quantity than the heat of young men, and the heat of young men is more intense in quality.” And this also is evident from the force with which the natural processes, such as digestion and growth of body, are carried on in children. For this reason the blood of infants and children may be compared to must, in which the coction leading to perfect ripeness has not yet begun, nor the movement towards fermentation taken place; the blood of young men may be compared to must, which has already fermented and made a hissing noise, and has thrown out abundant vapors and its superfluous parts, like wine which is now still and quiet and arrived at its full strength; and as to the blood of old men, it may be compared to wine which has now lost its strength and is beginning to grow vapid and sour.

Now the Small-Pox arises when the blood putrefies and ferments, so that the superfluous vapors are thrown out of it, and it is changed from the blood of infants, which is like must, into the blood of young men, which is like wine perfectly ripened: and the Small-Pox itself may be compared to the fermentation and the hissing noise which take place in must at that time. And this is the reason why children, especially males, rarely escape being seized with this disease, because it is impossible to prevent the blood’s changing from this state into its second state, just as it is impossible to prevent must (whose nature it is to make a hissing noise and to ferment,) from changing into the state which happens to it after its making a hissing noise and its fermentation. And the temperament of an infant or child is seldom such that it is possible for its blood to be changed from the first state into the second by little and little, and orderly, and slowly, so that this fermentation and hissing noise should not show itself in the blood: for a temperament, to change thus gradually, should be cold and dry; whereas that of children is just the contrary, as is also their diet, seeing that the food of infants consists of milk; and as for children, although their food does not consist of milk, yet it is nearer to it than is that of other ages; there is also a greater mixture in their food, and more movement after it; for which reason it is seldom that a child escapes this disease. Then afterwards alterations take place in their condition according to their temperaments, regimen, and natural disposition, the air that surrounds them, and the state of the vascular system both as to quantity and quality, for in some individuals the blood flows quickly, in others slowly, in some it is abundant, in others deficient, in some it is very bad in quality, in others less deteriorated.

As to young men, whereas their blood is already passed into the second state, its maturation is established, and the superfluous particles of moisture which necessarily cause putrefaction are now exhaled; hence it follows that this disease only happens to a few individuals among them, that is, to those whose vascular system abounds with too much moisture, or is corrupt in quality with a violent inflammation; or who in their childhood have had the Chicken-Pox, whereby the transition of the blood from the first into the second state has not been perfected. It takes place also in those who have a slight heat, or whose moisture is not copious; and to those who had the Chicken-Pox in their childhood, and are of a dry, lean habit of body, with slight and gentle heat; and who when they became young men, used a diet to strengthen and fatten their body, or a diet which corrupted their blood.

And as for old men, the Small-Pox seldom happens to them, except in pestilential, putrid, and malignant constitutions of the air, in which this disease is chiefly prevalent. For a putrid air, which has an undue proportion of heat and moisture, and also an inflamed air, promotes the eruption of this disease, by converting the spirit in the two ventricles of the heart to its own temperament, and then by means of the heart converting the whole of the blood in the arteries into a state of corruption like itself.¹

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