DISEASES WHOSE CAUSE HAS NOT BEEN ISOLATED 187 



Etiology. The disease is transmitted by contact, by 

 a third person, by toys, books, clothing, etc. The cause 

 is unknown, as is also the nature of the contagion. 



Morbid Anatomy. There are no characteristic ana- 

 tomic changes. The lymphatic glands are enlarged. 

 The eruptive areas of the skin show some leukocytic 

 infiltration. 



Morbid Physiology. There are no specific alterations 

 of function. Fever and catarrhal disturbances of the 

 mucous membranes are the prominent disturbances. 



SCARLET FEVER 



Definition. An acute infectious disease character- 

 ized by a scarlet eruption, sore throat, and high fever. 



Etiology. The exciting cause is unknown. Age is a 

 predisposing cause. It occurs most frequently from the 

 second to the tenth year; 90 per cent, of cases occur 

 before the tenth year. There is a great variation 

 of personal susceptibility. Some individuals are ap- 

 parently immune. The infecting agent is very resist- 

 ant, and infection is often conveyed by clothing, books, 

 toys, carpets, etc., months after the occurrence of the 

 disease. 



Morbid Anatomy. There are no specific pathologic 

 changes. The changes in the throat are those of any 

 simple inflammation. The internal alterations are those 

 due to fever and to pus organisms, which seem to always 

 complicate the disease. The spleen, liver, and Other 



