The rash consists first of small round or oval, rose-colored macules, which seem to be in the skin, coming up from beneath it, as it were. They disappear readily on pressure or on tension of the skin. When coalescence occurs, the lesions may resemble the blotches of measles. The macule at this stage is about from one-eighth to one-fourth of an inch in diameter, and its color is of an intense red which shows well at night, even by the light of a match. In less than twenty-four hours the centre of the macule becomes hard; and as this hardness increases, the lesion gradually rises above the skin. It is now changing into the papular stage. The macular stage lasts usually from eight to twenty-four hours. The papules continue to increase slowly in size, the apex becoming flattened or indented in some lesions. While this change is going on the redness of the macule forms an areola about the hard portion or central papule. This areola tends to get smaller as the papule gets larger, and at last is completely lost. If the pulp of the finger is passed over the papule, especially in its early stage, the latter seems to roll beneath it, giving the sensation of a small shot buried in the skin. When the papule is fully developed, the surrounding skin is put on the stretch, and the rolling sensation is lost, but the papule is so dense and hard that it is frequently described as “shotty.” The papule of varicella and of acne is not so dense and resisting as the papule of variola. The fully-developed papule in smallpox is rarely surrounded by a halo of congestion as it is in varicella, but in the modified form of smallpox this is not infrequently the case. The papule always arises from the centre of its halo like a bull’s eye, whereas in chicken-pox it arises from within the circumference, but not always in the centre. The halo of congestion in chicken-pox is always very broad and extensive, and is best seen upon the back. When a halo is present in smallpox it is very narrow and insignificant. The papule is usually fully developed in twenty-four hours. At the end of another twenty-four or thirty-six hours the apex of the papule shows a further change. It appears to be transformed from a solid to a fluid. The color also changes as the fluid increases, and the lesion appears bluish or purplish. The fluid continues to increase in amount until the papule is converted into a little blister or vesicle. As the change is going on, the height of the papule grows less and less, and when vesiculation is complete we have a broad, flat, umbilicated vesicle with a firm, dense base. To the touch these vesicles are firm and resisting, and the membranous covering is not easily broken, unless macerated by the perspiration due to heavy flannels.