But some phenomena preceding the outbreak of the pestilence are observed as coincidences by all authors. Gibbon thus writes: "I shall conclude this chapter with the comets, the earthquakes, and the plague which astonished or afflicted the age of Justinian." From the accounts given by this author, earthquakes for some years had been threatening and destroying many portions of the globe, {51} that in the ruins of cities and in the chasms of the earth, great was the sacrifice of human life. Constantinople, which suffered so severely from the plague is said to have been shaken for forty days. These great disturbances of the globe have been always looked upon as indicating other and important influences of a secret or hidden nature; these impressions on the minds of the people are traceable throughout the histories of all epidemics, and have been sufficiently distinct among the people of our own time, preceding and during the period of infliction. From this short notice of the Plague of 543, I pass to the ninth century, when Rhazes, the Arabian physician, endeavoured to enlighten the world on the subject of Small Pox.[19] In quoting his opinions, I am not to be understood as subscribing to them, but merely endeavouring to point out some peculiar and interesting observations. First, then, Rhazes attributes the disease to a condition of the blood, which he thus describes, to shew how it happens that in infancy and childhood the disease is most prevalent, and that old age is {52} least liable to the affection.[20] "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 vapours 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 putrifies and ferments, so that the superfluous vapours 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 at that time."