()34 FILTERABLE VIRUSES— RICKETTSIA 
cranial inoculations of the virus of poliomyelitis. It is stated that 
the serum of a horse immunized with this coccus, injected early into 
human cases, resulted in a pronounced reduction of symptoms, and the 
prevention of paralysis. It is believed by many that the organism is 
not a secondary invader, as has been claimed by some observers, and 
that it has definite etiological significance in the causation of acute 
anterior poliomyelitis. Final judgment upon the organism awaits 
additional study in comparison with the filterable virus of Noguchi and 
Flexner in a series of identical cases. 
Lethargic Encephalitis. —The disease known as epidemic encephali- 
tis, lethargic encephalitis, and popularl}' but incorrectly referred to 
as "Sleeping Sickness," appears to be one not recognized in the United 
States prior to 1918. It was, however, recognized in Europe about 
two years earlier. 
There are several prodromal symptoms,^ which are rather general 
and indefinite, consisting of malaise, chilly sensations, headache, 
occasionally nausea, and not infrequently a catarrhal rhinitis. Fever 
is irregular. The more significant symptoms are ptosis and diplogia, 
due to involvement of the third nerve, and the gradual development 
of a state of lethargy which is in a majority of cases the most distinctive 
symptom. The lethargic state varies in different individuals from a 
mere reduction in the ability to remain mentally alert to a state of 
stupor or of coma. The duration of the lethargic state is variable; 
it ma}^ pass away within a week or it may even extend to ten or even 
fifteen weeks. The mortality is variable; from 20 to 40 per cent of 
recognized cases die. The pathological changes are localized chiefly 
in the brain and cerebellum; the medulla and even the upper end of 
the spinal cord may be involved. There is capillary congestion, 
hemorrhage and later degeneration and necrosis, accompanied by 
perivascular round-cell infiltration. The region surrounding the third 
ventricle and the aqueduct of Sylvius, together with the optic thalamus, 
pons and medulla, is mostly aftected.- 
The etiology of the disease is still obscure. Loewe and Strauss^ 
have reported the discovery, isolation, cultivation and successful 
infection of experimental animals with a virus which will pass unaltered 
through the pores of suitable Berkefeld and Pasteur filters. The 
virus they obtained resembles in a very striking manner the filterable 
virus of poliomyelitis. The methods of isolation and of culture which 
are successful in the separation of the virus of poliomyelitis gave posi- 
tive results in the isolation of the minute, globoid body which ai)pears 
to be associated with lethargic encephalitis. 
The washings from nasal cavities, passed through Berkefeld filters, 
' See Report No. 121 to the Local Government Board" upon Encephalitis Lethargica, 
London, 1918, for clinical details. 
2 See Bassoe: Epidemic EncephaHtis (Noma): Jour. Am. Med. Assn., 1919, 72, 971 
for pathological anatomy. 
3 Jour. Infec. Dis., 1919, 25, 1920, 378; 27, 250. 
