232 DISEASES OF UNKNOWN ETIOLOGY 



Typhus Fever. Although this condition is not under- 

 stood clearly, it now seems that body lice, flies, and 

 ticks transmit it. It is a filterable virus also and can 

 be transmitted to monkeys. A bacterium has lately 

 been found, however, which in certain ways seems to 

 have something to do with the disease. Typhus 

 fever exists in America in a mild form known as Brill's 

 disease. 



Scarlet Fever. This is variously ascribed to protozoa 

 and to streptococci; neither claim is well supported. 

 The virus is in the blood and can be transmitted to 

 monkeys at the height of the attack; in these animals 

 a fever occurs, but no disease typical of scarlatina. 

 The virus may be also in the peeling skin. 



Measles. As in the former disease various micro- 

 organisms have been held responsible but no certain 

 one can be convicted. The virus in the blood of 

 patients, in their nasal and buccal secretions, and 

 when any of these are transferred to a monkey a fever 

 quite like that of the human disease will develop. 

 The viruses of both diseases are filterable. 



Poliomyelitis. This is an acute apparently infectious 

 disease characterized by a mild constitutional illness 

 followed by gradually appearing and progressing 

 paralyses. It may be sporadic or appear in epidemics. 

 The infective agent and its mode of transmission are 

 not known. It probably enters by the nose and 

 throat. The virus is present in the blood, lymph 

 glands, and especially in the central nervous system. 

 It is so small that it will pass through porcelain filters 

 such as are used for water purification. The disease 

 may be reproduced in monkeys by injecting this virus 



