Here also we are, as yet, in the dark as to the form of the infective agent. It is volatile, so that infection occurs through the air, by inhalation. It is to be inferred that the infective agent is present and multiplies in the blood. There is no constant local lesion, and the red blood-corpuscles show very striking changes in shape and indications of disintegration. The eruption in the skin is rather in the form of a passive hyperemia, with disintegration of the blood so as to stain the tissues, than of a true inflammation. Hence it partly persists after death as stains or blotches. The skin may show evidences of a more considerable disintegration of the blood in the form of a general staining almost amounting to jaundice.