482 W. SCHAFER 



The chemical studies were made on virus material, which was obtained 

 from extracts of infected chick embryos by several cycles of high- and low- 

 speed centrifugation (Taylor et al., 1943). About 0.5 mg. of purified end- 

 product was obtained from one gm. of embryo tissue. Although this product 

 seemed to be homogeneous in the electron microscope and the analytical 

 ultracentrifuge, its purity is questionable, since one infective dose (JD50 in 

 mice) corresponded to an amount of protein equivalent to about 250 particles 

 of 152 X 10^ particle weight. Furthermore, the high frictional ratio (f/fo) 

 of 2.3 does not agree with the spherical form of the particles observed in 

 the electron microscope, but suggests that some impurity of higher viscosity 

 was present. According to the serological studies (Engel and Randall, 1947), 

 this seems to be a normal component of the tissue. 



Chemical investigations (Sharp et al., 1940; Taylor et al., 1943; see Beard, 

 1948) showed that these preparations of infective particles of equine enceph- 

 alomyelitis contained protein, nucleic acid, lipids, and a small fraction of 

 carbohydrate. 



The nucleic acid is of the ribose type and comprises about 4.4 % of the 

 particle. Assuming that the impurities represent a relatively insignificant 

 fraction, the nucleic acid found corresponds to one RNA molecule (Gierer, 

 1957), on the assumption of a weight of 50 X 10^ for the virus particle. The 

 liigh lipid content of 54 % is striking, and is composed mainly of phospholipid 

 (35 % of the whole virus). Cholesterol and neutral fats are also present. 

 The loss of infectivity after treatment of the equine encephalomyelitis virus 

 particles with ether (Birch, 1941; Sulkin and Zarafonetis, 1947), suggests that 

 lipid is an integral part of these units. 



On the basis of a dextrose standard the total carbohydrate content, includ- 

 ing the nucleic acid ribose, was only 4 %. 



There is no mention in the literature of the existence of a S antigen in 

 encephalomyelitis. 



No enzymes have been reported to be associated with the equine encephalo- 

 myelitis virus or with any of the other small viruses described above. 



B. Viruses of Medium Size 



1. Influenza and Fowl Plague Viruses 



Most interest in the medium-sized viruses has been centered around the 

 myxovirus group. All the representatives of this group are capable of ag- 

 glutinatmg red blood cells. The infective particles are not as uniform in size 

 as those of the smaller viruses. Influenza and fowl plague are the myxoviruses 

 that have been analyzed chemically most extensively. Since they are sero- 

 logically related (Schafer, 1955b; Nitzschke, 1956; Schafer, 1957b), they will 

 be considered together. 



