74 F. B. BANG 



such descriptions. Most of these, however, are of little value in cell path- 

 ology, for they are usually based on smear preparations. Miyagawa et al. 

 (1936) described the occurrence of granulocorpuscles in tissue culture cells. 

 The complete cycle was followed by Rake and Jones (1942) in infected yolk 

 sac cells. During the first 6 hours, occasional virus bodies or elementary bodies 

 could be seen in smears or sections, and were thought to represent the 

 original massive inoculum. This apparent virus then disappeared, and 

 initial bodies of about 1 /z in diameter were found in the cell. These seemed to 

 divide like cocci and to form pairs. Later they appeared in vesicles sur- 

 rounded by a thin matrix. After 20 hours of infection, bright red elementary 

 bodies were found within large green plaques (Noble's stain). Several plaques 

 might occur within one cell. Some individual plaques attained a diameter of 

 4 to 7 //.. 



There have been several studies with the electron microscope, but in 

 general these have not been adequately correlated with simultaneous obser- 

 vations on living or light microscopic stained material. Gaylord (1954) studied 

 the appearance of the intracellular virus in cells of the chicken chorioallantoic 

 membrane at 48, 72, and 96 hours after heavy inocula. Since the minimal 

 time here exceeded by far the stages of infection described by Bland and 

 Canti (1935), no true sequence of intracellular changes could be determined. 

 However, the increased resolution afforded by electron microscopy in this 

 and in subsequent studies brought out a number of points that were not clear 

 previously. The inclusions contain a collection of particles varying from 

 large, rather homogeneous ones (which seem to be 250 to 500 m/x in cross 

 section and would then correspond to the large form of the virus) to denser, 

 smaller particles with dark centers which are scattered among them. These 

 latter are identical in appearance with the virus elementary body which has 

 been carefully identified by Crocker (1954) by a series of correlative studies 

 of virus suspensions in the electron microscope. Undoubtedly, they are the 

 smaller elementary bodies. Intermediate forms and so-called incomplete 

 forms are also described (Tajima et al., 1957). Secondly, the virus may appear 

 free in the cytoplasm or be contained in a vacuole in the cytoplasm of the host 

 cell, as has been seen in living cells. The wall of the vacuole has no character- 

 istic different from the cytoplasmic membrane. The host cytoplasm, mito- 

 chondria, and nucleus are free of changes. Although the latest study (Tajima 

 et al., 1957) does include samples taken at frequent intervals after infection 

 with large amounts of virus, no certain sequence of changes of the virus 

 elementary bodies was demonstrated. 



It seems clear from the sum of these studies that two forms of virus 

 particles may be identified. First is the larger form (Bedson and Gostling, 

 1954; Bland and Canti, 1935; Swain, 1955) and, second, the smaller character- 

 istic elementary bodies. The relationship of the latter to the plaques is not 



