VARIOUS FORMS OF ERUPTION (RASH), &c., OF THE SKIN.
The pimple or papule is a solid elevation above the level of the skin, between a millet need and a lentil in size. It apparently contains no fluid. It may be of the colour of the natural akin, reddish, bluish, or black, &c. Pimples ire commonly connected with the glands of the hair, due to effusion of material prevented from escaping, or they may be due to inflammatory swelling of the papillae of the true skin. Their presence gives a feeling of roughness to the skin, Ind may occasion severe itching and tingling.
The vesicle is an elevation of the upper horny layer of the skin by fluid accumulated between it and the deeper layers. It is of the size of a pimple, and the fluid is clear or milky. The thin covering may burst and the fluid escape, or it may evaporate, or the clear fluid may become yellow and a pustule be formed.
A pustule is the same as a vesicle, but instead of clear fluid it contains yellow matter—pus. A vesicle becomes a pestle if the clear contents of the vesicle alter their character, as they often A bleb or bulla is the same as a vesicle ex cept in size. They may be as large as walnuts, or even hen's eggs, or still larger. The contents of the bleb may, however, be pus.
A tubercle is a solid swelling larger than that to which the term pimple is applied, but of a similar kind.
A wheal is the term applied to a raised por tion of skin of greater extent than thickness. It may be of varying shades of red, and is gen erally flat. It is due to swelling in the upper layer of the true skin itself.
A tumour is a solid swelling, in size be tween a walnut and a man's fist, situated in the deeper layers of the skin.
Lastly, there is the stain or maeule, or spot, caused by a change in the ordinary colour of the skin. Spots may be of varying colour, white, red, blue, yellow, brown, &c., and of very different sizes. They are not raised above the surface. They may be produced by blood being poured out in the substance of the skin at mere points here and there or in patches.
The blood spot passes through changes in colour, blue, green, and yellow, before it dis appears.
These various forms of eruption are not necessarily separate and distinct kinds ; for the pimple may become a vesicle, and the vesicle may change to a pustule, and the condition that produces the pimple will give rise to the tubercle if a larger extent of surface be affected. Similarly the difference between a vesicle and a bleb consists simply in the size of the area affected.
Moreover, scratching, rubbing, &c., effect alterations in the appearance of the eruption. In itchy diseases frequently the original form of the eruption is not recognizable because of the effects of scratching. The heads of pimples may be knocked off so that blood oozes in drops and hardens on the pimple, changing its ap pearance. The skin covering vesicles, pustules, &c., may be removed by scratching, and raw surfaces remain from which clear fluid, perhaps mixed with blood, oozes. This is called an excoriation.