The cutaneous affection is not a mere hypermia. It is also an exuda tion into the rote mucosum. The cells in this situation are proliferated and swollen, and the sweat-glands may be stuffed and distended by their increased cellular contents. Serous effusions with migration of leucocytes may also occur. The lymphatic glands, especially those of the neck, are enlarged ; the lymphoid cells disappear, and in places large giant cells be come developed containing many nuclei.
The kidney presents the characters of acute Bright's disease. The whole organ is congested, and important changes are noticed in the glom eruli, the small arteries, and the convoluted tubes. According to Dr. Klein, these changes take place very early, so that in the first week of the disease proliferation of the nuclei in the Malpighian tufts and in the muscular coat of the arteries can be detected, as well as hyaline degeneration of the intima. At the same time there is hyaline thickening of the walls of the Malpighian capillaries, and cloudy swelling of the epithelium in some of the convoluted tubes. At a later stage the cloudiness and swelling of the tubal epithelium increases, and fatty degeneration takes place ; infiltra tion of lymphoid cells occurs into the interstitial tissue around the tubules ;, and the tubules themselves are filled with hyaline casts.
In cases of uremia the blood is sometimes found to contain an enor mous excess of urea. In a case reported by M. D'Espine of Geneva, in which venesection was employed, the blood was found to contain 3.3 parts of urea per thousand, cr about twelve times the normal quantity. The potash salts, also, were increased to three times the natural proportion, and of this two-thirds was contained in the serum, and not, as in healthy blood, in the red corpuscles. From the experiments of Feltz and Bitter, and others, it appears probable that.the symptoms of ummic poisoning are due not to the retained tu-ea, but to the excess of potash salts in the blood.
Symptoms. —After exposure to infection a period of incubation pre cedes the actual outbreak of the fever. This stage is of very variable duration. It may last only twenty-four hours, or be prolonged to a week or more. Probably six days may be taken as the ordinary duration of this period.
Different cases of scarlatina vary so much in severity and in the vio lence of special symptoms that it will be convenient to divide the disease into two chief forms : The common mild form and the malignant form. Afterwards the complications and sequelae will be described.
In the common form the invasion of the disease is abrupt. It begins with a chill ; the child complains of sore throat, and generally vomits. Sometimes there are nervous symptoms, and in exceptional cases the disease may be introduced by a convulsion or a state resembling coma. The tongue is generally furred at the back, red at the tip and edges ; the appetite is lost, and there is thirst. The skin is hot, and the pulse rises to
130°, 140°, or even higher. The rash sometimes appears within a few hours of these early symptoms : occasionally it is itself one of the early phe nomena ; and again in rare cases it may be delayed for three or four days, or, it is said, even for a week. As a rule it is noticed within twenty-four hours of the beginning of the disease. The temperature rises progres sively through the invasion stage until the rash appears. The pyrexia is not, however, excessive. In the case of the little girl, before referred to, who was taken with scarlatina while in the hospital, her temperature had always been normal, but one evening it was noticed to be 100.2°. The next morning it was 101.2°, and the child vomited several times. Toward the evening the rash appeared, and the mercury reached 103°. In another ease—a little boy aged eight months, who was teething—the temperature for several days had been One morning it rose 102.2° ; he vomited, and in a few hours the rash appeared. To the hand, perhaps, the skin gives the impression of being hotter than it actually is, for the heat is often accompanied by a peculiar dryness, which gives a burning character to it like that of pneumonia. Tested by the thermometer, the temperature will be rarely found to exceed 105°.
With the appearance of the rash the invasion stage comes to an end and the eruptive stage begins. The rash first appears as scarlet points, not elevated above the surface. These are closely set, and their borders, which are paler than the centre, unite so as to produce, when fully devel oped, the appearance of a uniform pink ground clotted thickly over with scarlet points. The rash rarely affects the face to the same degree that it does the rest of the body, and differs in this respect from the eruption of measles. Usually the region about the mouth is comparatively free, and contrasts by its paleness with the deep red tint of neighbouring parts. The colour of the rash disappears on pressure of the finger. When the eruption is confluent, as it is in a typical case, no intervening healthy skin can be seen. Often, however, the eruption is not confluent. The puncta are then more or less isolated, and may be separated by spaces in which the skin has the normal colour. The rash may be confluent in some places, not in others. On the cheeks, neck, chest, abdomen, and inner aspect of the arms and thighs, coalescence of the neighbouring puncta is usually complete. In other parts the spots may be more or less isolated. Some times the eruption is everywhere discrete. The puncta are then usually larger ; and if at the same time the temperature is only slightly elevated and the sore throat insignificant, great doubt may be entertained as to the nature of the disease ; especially as when thus discrete the spots are often a little elevated. These cases have been mistaken for measles.