[120] Page 40, 41. See also p. 111, 230, 231. vol. I. In Baltimore, the small-pox in the natural way was attended with unusual malignity and mortality, occasioned by its being combined with the reigning yellow fever. It has been urged as an objection to the influence of powerful epidemics chasing away, or blending with fevers of inferior force, that the measles sometimes supplant the small-pox, and mild intermittents take the place of fevers of great malignity. This fact did not escape the microscopic eye of Dr. Sydenham, nor is it difficult to explain the cause of it. It is well known that epidemics, like simple fevers, are most violent at their first appearance, and that they gradually lose their force as they disappear; now it is in their evanescent and feeble state, that they are jostled out of their order of danger or force, and yield to the youthful strength of epidemics, more feeble under equal circumstances of age than themselves. It would seem, from this fact, that an inflammatory constitution of the air, and powerful epidemics, both in their aggregate and individual forms, possessed a common character. They all invade with the fury of a savage, and retire with the gentleness of a civilized foe. It is agreeable to discover from these facts and observations, that epidemic diseases, however irregular they appear at first sight, are all subject to certain laws, and partake of the order and harmony of the universe. The action of the miasmata upon the body, when, from the absence of an exciting cause, they did not produce fever, was the same as I have elsewhere described. The sensations which I experienced, in entering a small room where a person was confined with this fever, were so exactly the same with those I felt the year before, that I think I could have distinguished the presence of the disease without the assistance of my eyes, or without asking a single question. After sitting a few minutes in a sick room, I became languid and fainty. Weakness and chilliness followed every visit I paid to a gentleman at Mr. Oellers's hotel, which continued for half an hour. A burning in my stomach, great heaviness, and a slight inflammation in my eyes, with a constant discharge of a watery humour from them for two days, succeeded the first visit I paid to Mrs. Sellers. These symptoms came on in less than ten minutes after I left her room. They were probably excited thus early, and in the degree which I have mentioned, by my having received her breath in my face by inspecting her tonsils, which were ulcerated on the first attack of the fever. I formerly supposed these changes in my body were proofs of the contagious nature of the yellow fever, but I shall hereafter explain them upon other principles.