ACUTE INFECTIOUS DISEASES. 



resembles measles, while the high fever, the throat affection, and the 

 dropsy, which often follows, resemble the course of scarlatina. By 

 rubeola morbillosa is meant a form of measles where the exanthema 

 is confluent, and resembles that of scarlatina, while the affection of 

 the respiratory mucous membrane and the escape of the pharyngeal 

 mucous membrane leave no doubt of the morbillous nature of the 

 disease. 



CHAPTER IV. 



SMALL-POX VARIOLA PETITE VEROLE. 



ETIOLOGY. Small-pox spreads solely by contagion ; at least, any 

 other cause of its extension and a spontaneous development of variola 

 poison is very improbable, as we can always trace the contagion where 

 there is no peculiar obstacle in the way of our seeking it. Small-pox 

 poison, which we only know from its effects, is contained in the con- 

 tents of the pustules, and in the perspiration of patients having the 

 disease. This is proved on the one hand by successful vaccination 

 with the contents of the pustules, and on the other by the contagion, 

 which, in most cases, results without immediate contact with small- 

 pox patients. The poison is most active at the period when the 

 clear contents of the pocks begin to turn cloudy. The negative 

 results of attempts at vaccination with the blood and secretions of 

 small-pox patients, seem to prove that the poison is not contained in 

 these fluids. Variola poison is very tenacious of vitality ; it is not de- 

 stroyed by drying ; it clings for a long time to objects that have been 

 near a patient with the disease, and, when protected from the air, it 

 remains active for years. The same poison induces the severe forms 

 of variola as well as the mild ones of varioloid. If a healthy person 

 be infected by a patient with varioloid, he may have a severe variola, 

 and the reverse. The different effect of the poison, that is, the un- 

 equal intensity of the symptoms, appears chiefly due to the greater or 

 less susceptibility of the patient exposed to the poison. This indi- 

 vidual predisposition has always been very unequal ; for, in former 

 centuries also, there were some persons who were perfectly insuscep- 

 tible to variola poison, so that they could expose themselves to it with 

 impunity ; there were others in whom the susceptibility was so slight 

 that they were only attacked by the milder forms (varioloid) ; wliile, 

 in most persons, it was so decided that, on exposure, they were affected 

 with the severe form of the disease (variola). The liability to small- 

 pox, which, with the above exceptions, is common to all mankind, well 

 and sick, young and old (even the foetus), men and women, expires al- 



