Notes on Animal Diseases

Abstract

There exists amongst mammals and birds a group of closely related diseases which are characterized by the development, usually on the skin, of a lesion called a pox, or variola,a lesion which has been recognized since ancient times. In mammals it begins typically as a small red spot. Twenty-four hours later the upper layers of the skin in the Centre of the spot thicken and, after a further day, a vesicle containing a drop of clear, yellowish, serous fluid develops. Later the surface of the vesicle becomes depressed and the contents cloudy. After several more days the contents of the vesicles dry and the swelling disappears from the skin. Eventually the scab drops off. This a scab is very rich in the causal virus and is the vehicle by which the disease is spread