ACUTE ANTERIOR POLIOMYELITIS 919 



Although a great many studies have been made to trace the infec- 

 tion of one case to exposure to another, such attempts have failed in 

 most instances, and it seems fairly well established that there is great 

 variation in the susceptibility of individuals to the disease. Whether 

 this depends upon previous mild attacks of the variety spoken of 

 above or whether it is a congenital difference, cannot be stated. 



ENCEPHALITIS LETHARGICA 



It is difficult to say whether the disease which we now speak of 

 as Lethargic Encephalitis is identical with the conditions formerly 

 described as "sleeping sickness," "Schlaf Krankheit," etc. Camera- 

 rius, whom we quote from Smith, 19 is said to have described an epi- 

 demic disease which occurred in Germany in 1712 which probably 

 represents the same condition. In 1768 and in. 1835 similar epidemics 

 seem to have occurred in the trail of influenza outbreaks, a fact which 

 is of considerable importance in view of the fact that recent interest- 

 in the disease dates from the occurrence of many cases of lethargic 

 encephalitis which followed in the train of the last influenza epidemic. 

 After the epidemic of 1889, relatively few typical cases of what we 

 now speak of as lethargic encephalitis were reported, though nervous 

 complications were apparently very common. During the later stages 

 of the great war epidemic of influenza, cases began to appear in many 

 different places which, at first, were either mistaken for poliomyelitis 

 or undiagnosed before death. We remember ourselves seeing two cases 

 in soldiers during this period in which diagnosis was doubtful and 

 which we now believe to have been lethargic encephalitis. 



One of the first systematic reports is that of Economo 20 who de- 

 scribed an outbreak of the disease in Vienna in 1917. In 1918 an 

 outbreak occurred in Great Britain, which was studied and reported 

 by Wilson, 21 Hall, 22 Herringham, and others. (The onset of the 

 disease in America was dealt with in an editorial in the Journal of 

 the American Medical Association, 72, 1919, 414.) In speaking of the 

 distribution of the disease during this last epidemic, Smith states that 

 the first cases occurred in Central Europe in 1917, appeared in France, 



19 Smith, U. S. Pub. Health Eeport, No. 6, Vol. 37, February, 1921. 



20 Economo, Wien. klin. Woch., 30, 1917, 581. 



21 Wilson, Lancet, 2, 1918. 



22 Hall, Brit. Med. Jour., 2, 1918, 467. 



