FAMILY ERRONACEAE 



1255 



comma-shaped particles. Sedimentation 

 constant, mean 265.5 X IQ-i^ ± 5.4 X 

 10-13 (range 252 to 276 X IQ-") . Specific 

 volume 0.864. Molecular weight of lipo- 

 nucleoprotein complex behaving as the 

 virus calculated as 152 million, approxi- 

 mately 250 particles giving 50 per cent 

 infection; material contains 4 per cent 

 carbohydrate. Absorption of ultraviolet 

 light reaches a peak at about 2600 A., a 

 broad minimum at about 2450 A., and an 

 increase at 2200 A. 



Strains : The Western strain (so-called 

 Western equine encephalitis virus) may 

 be considered as type of a large group of 

 variants met in nature ; some produce 

 clinically milder disease than others 

 (Birch, Am. Jour. Vet. Res., 2, 1941, 

 221-226) ; they may change in virulence 

 on passage in experimental hosts. The 

 Eastern strain (so-called Eastern equine 

 encephalitis virus) has been studied ex- 

 tensively also, and has been found to 

 differ from the type strain especially : in 

 more rapid course of induced disease in 

 the horse ; in being experimentally trans- 

 missible to sheep, pig, dog, cat and the 

 European hedgehog; in its localization in 

 eastern coast states and absence from the 

 area between California and Wisconsin, 

 where the type strain is found ; in failure 

 experimentally to infect A'edes aegypti 

 unless inoculated into body cavity by 

 needle punctui'e, whereupon it persists 

 and can be transmitted ; and in failure of 

 cross-neutralization with the western 

 strain. A strain produced by serial 

 passage in pigeons is reported to have 

 caused no obvious reaction in horses but 

 to have induced the formation of neu- 

 tralizing antibodies. A Venezuelan 

 strain differs from the type in comple- 

 ment-fixation reactions; it induces in 

 man a mild disease, characterized by 

 malaise, fever, headache or drowsiness, 

 and uneventful recovery (Casals et al.. 

 Jour. Exp. Med., 77, 1943, 521-.530). 



Literature: Bang, Jour. Exp. Med., 

 77, 1943, 337-344; Bauer et al., Proc. Soc. 

 Exp. Biol, and Med., 33, 1935, 378-382; 

 Beard et al.. Science, 87, 1938, 490; Birch, 



Am. Jour. Vet. Res., 2, 1941, 221-226; 

 Casals and Palacios, Science, 94, 1941, 

 330; Covell, Proc. Soc. Exp. Biol, and 

 Med., 32, 1934, 51-53; Cox, ibid., 33, 1936, 

 607-609; Cox and Olitsky, Jour. Exp. 

 Med., 63, 1936, 745-765; ^4, 1936, 217-222, 

 223-232; Cox et al., U. S. Pub. Health 

 Service, Public Health Rept., 66, 1941, 

 1905-1906; Davis, Am. Jour. Hyg., 32 

 (C), 1940, 45-59 ; Eklund and Blumstein, 

 Jour. Am. Med. Assoc, 111, 1938, 1734- 

 1735; Feemster, Am. Jour. Public Health, 

 28, 1938, 1403-1410; Finkelstein et al.. 

 Jour. Inf. Dis., 66, 1940, 117-126; Fother- 

 gill and Dingle, Science, 88, 1938, 549- 

 550; Fothergill et al., New England Jour. 

 Med., 219, 1938, 411 ; Giltner and Shahan, 

 Science, 78, 1933, 63-64; Jour. Am. Vet. 

 Med. Assoc, 88, CN.S. 41), 1936, 363-374; 

 Graham and Levine, Am. Jour. Vet. Res., 

 2, 1941, 430-435; Grundmann et al.. Jour. 

 Inf. Dis., 72, 1943, 163-171 ; Havens et al., 

 Jour. Exp. Med., 77, 1943, 139-153 ; Higbie 

 and Howitt, Jour. Bact., 29, 1935, 399- 

 406; Howitt, Jour. Inf. Dis., 55, 1934, 

 138-149; 61, 1937, 88-95; 67, 1940, 177- 

 187; Science, 88, 1938, 455-456; Howitt 

 and Van Herick, Jour. Inf. Dis., 71, 1942, 

 179-191; Kelser, Jour. Am. Vet. Med. 

 Assoc, 82, 1933, 767-771 ; King, Jour. Exp. 

 Med., 71, 1940, 107-112; 76', 1942, 325-334; 

 Kitselman and Grundmann, Kansas Agr. 

 Exp. Sta., Tech. Bull. 50, 1940, 1-15; 

 Merrill and TenBroeck, Jour. Exp. Med., 

 62, 1935, 687-695; Meyer et al., Science, 

 74, 1931, 227-228; Mitchell et al., Cana- 

 dian Jour. Ccrmp. Med., 3, 1939, 308-309; 

 Morgan, Jour. Exp. Med., 74, 1941, 115- 

 132; Morgan et al., ibid., 76, 1942, 357- 

 369; Olitsky et al., ibid., 77, 1943, 359- 

 374; Remlinger and Bailly, Compt. rend. 

 Soc. Biol., Paris, 121, 1936, 146-149; 122, 

 1936, 518-519; 123, 1936, 562-563; Sabin 

 and Olitsky, Proc. Soc. Exp. Biol, and 

 Med., 38, 1938, 597-599; Sellards et al., 

 Am. Jour. Hyg., 33 (B), 1941, 63-68; 

 Shahan and Eichhorn, Am. Jour. Vet. 

 Res., 2, 1941, 218-220; Sharp et al., Proc. 

 Soc. Exp. Biol, and Med., 51, 1942, 206- 

 207; Arch. Path., 36, 1943, 167-176; 

 Syverton and Berry, ibid., 34, 1936, 822- 



