DISEASES OF UNKNOWN ETIOLOGY 421 



Chicken Pox 



The organism responsible for the disease chicken pox has 

 not been determined. It is probably related to the organism 

 which causes smallpox, although, of course, entirely distinct. 

 The eruptions of chicken pox are more superficial and do 

 not result in the pitting and scars so characteristic of small- 

 pox. 



Measles 



Three, possibly four, distinct types of measles are known. 

 The most common are the so-called little red measles and 

 the German measles. The causal organisms of these dis- 

 eases are not known. They are highly contagious. The 

 incubation period is usually 9 or 10 days. The symptoms 

 begin with headache, fever and sore throat or "cold in the 

 head," with a rash which develops about the fourth day. 

 Characteristic spots appear in the mucous membrane of the 

 mouth. Methods of immunization against the disease are 

 not known. The disease is passed on by more or less direct 

 contact. 



Scarlet Fever 



This is an acute, highly contagious disease showing a 

 diffuse erythematous skin eruption. There is usually a 

 catarrhal, croupous or a gangrenous inflammation of the 

 throat, and fever. The causal organism is not known. 

 Streptococci are very common as secondary invaders to the 

 disease and many of the sequelae of the disease are due to 

 these organisms. 



Infantile Paralysis 



This disease, known also as acute anterior poliomyelitis 

 or the Heine-Medin disease, has been known for nearly a 

 hundred years in Europe and has caused several epidemics 

 in recent years in the United States. Plexner and Lewis in 

 1909, showed the causal organism to be a filterable virus. 



