ACUTE INFECTIOUS DISEASES. 



those over two years old are most susceptible to the disease ; but even 

 adults, who have not had scarlatina during childhood, are often at- 

 tacked by it, and cases occur even in old age. In very large cities it 

 seems never to disappear entirely ; we do not know why the disease 

 occasionally spreads, and why, after occurring sporadically for a year, 

 it should suddenly break out into an epidemic. Nor do we know the 

 causes of the differences between epidemics in regard to the mildness 

 or malignancy of the attacks. Epidemics of scarlatina occur chiefly > 

 but not exclusively, in autumn and spring ; they succeed each other at 

 longer or shorter intervals, and are of very variable duration. 1 



ANATOMICAL APPEARANCES. The anatomical changes in the skin 

 during life are those of a very extensive erythematous inflammation, 

 consisting of a very intense hyperaemia and an inflammatory cedema 

 of the superficial layers of the cuticle. The redness of the skin caused 

 by the hyperaemia begins as numerous small points, close together, 

 which soon unite and form an even redness (scarlatina Icevigata). Far 

 more rarely the redness is limited to a few spots of variable size and 

 irregular shape, or the surface is pale red, with some darker red spots 

 over it (scarlatina variegata). More rarely than in measles, collections 

 of inflammatory exudations at circumscribed spots form small papules 

 (scarlatina papulosd) ; on the other hand, exudation effused on the 

 surface frequently elevates the epidermis to numerous small vesicles 

 (scarlatina miliaris seu vesicularis), or to larger vesicles filled wit> 

 limpid or cloudy-yellow liquid (scarlatina pemphigoidea seu pustulosd) 

 In malignant cases, the hyperaemia of the skin is occasionally accom- 

 panied by more or less extensive haemorrhages, causing petechiae and 

 extensive ecchymoses. If death occurs at the height of the scarlatina, 

 the skin of the cadaver often appears thickened and hardened by infil- 

 tration, and we frequently find dried vesicles and dark-colored petechiae 

 on it, that have not disappeared after death as the hyperaemia has done. 



Inflammation of the pharyngeal mucous membrane is induced by 

 scarlatina poison just as often as inflammation of the cutis is. The 

 most frequent form of this pharyngitis is the catarrhal, in which the 

 mucous membrane of the palate, tonsils, and pharynx, is dark red, 

 swollen, at first dry, but subsequently covered with quantities of mu- 

 cus. In malignant epidemics, scarlatina is not unfrequently localized 

 ;n the pharyngeal mucous membrane as a diphtheritic inflammation ; 

 in such cases, the fauces and pharynx are at first covered with gray 

 plaques, which cannot be wiped off from the mucous membrane, be- 

 cause they are due to infiltration of its tissue with fibrinous exudation. 

 After lasting for a short time, this infiltration causes necrosis of the 

 patches of membrane, which are thrown off as discolored, badly-smell 

 ing sloughs ; and irregular losses of substance, covered with disinto 



