The relations of the local lesions and general symptoms to the infective agent are, in this disease, obscure and complicated, and are not likely to be cleared up till the infective agent itself is discovered. As yet no form of microbe has been demonstrated as the causative agent in scarlet fever. There are two pronounced seats of local lesion, the fauces and the skin. In the former, which is presumably tjie primary seat, an acute inflammation, usually with necrosis, is present, and the process is sometimes severe and destructive (Scarlatina anginosa). In the skin the lesion is an acute inflammation with little more than an active congestion, so that the skin presents little change when examined after death. The infective agent is undoubtedly present in the fauces, and there can be little doubt also that it passes into the blood. The lesion in the skin might be the result of the action of toxines, but the subsequent infective nature of the desquamated epidermis (which, however, some observers question) would indicate that the infective agent is present in the blood and carried to the skin. Sometimes the symptoms point to a high degree of intoxication, so that, with very little local lesion, there may be a very severe attack, fatal in a few days. These cases are scarcely explicable except on the supposition of an agent multiplying with great vigour in the blood. To the local lesions may be added that of the kidney (see under Diseases of the Kidneys), which is presumably due to the toxine. It consists in an inflammation, concentrated on the glomeruli in the early stages of the fever, but affecting the whole secreting structures in many cases. This affection of the kidneys may lay the basis for Bright's Disease. The local affection in the throat is often the seat of invasion by the ordinary septic microbes, more particularly the streptococcus pyogenes. It cannot as yet be determined how far the local lesion may be due to this invasion or to the primary agent, nor can it be stated how far the general symptoms, and even the local lesions in the kidneys, are due to septic intoxication. It is a case of mixed infection. The great destruction of tissue, involving in some cases the structures of the middle ear, point either to a special virulence in the infective agent, or to an extreme degree of potency in the mixed infection.