104 F. B. BANG 



cell by means of long fibrils. The intracellular fluid vacuoles, which develop 

 in tissues infected with the larger viruses, may be considered as a way of 

 separating parasite from host cytoplasm. The loss of osmotic competence of 

 the cell is reflected in ballooning of the internal membrane system (endo- 

 plasmic reticulum) and the development of fluid vacuoles between the nucleus 

 and the cytoplasm. 



4. A series of electron microscope studies, particularly with the myxo- 

 viruses, has focused interest on the changes occurring at the cell surface. 

 From this we have inferred that virus release, and perhaps maximum virus 

 activity, occurs here. These data tell us nothing about where the various 

 parts of the virus are synthesized. Indeed, interpretation of some morpho- 

 logical data on herpes has suggested that the early virus forms are made in 

 the nucleus and that they acquire more complete clothing as they progress 

 from nucleus to cytoplasm to the surface of the cell. The conclusiveness of a 

 given interpretation may be hazardous, as witness the fact that two strains 

 of the same virus may produce different cellular lesions (Bang, 1953b; 

 Bankowski and Hyde, 1957), contingent upon their respective virulence. 

 Furthermore, the same virus may produce different cellular lesions in dif- 

 ferent cell types. This latter circumstance has been nicely shown in the infec- 

 tion of rabbit fibroblasts and epithelium by the virus of myxoma by Chap- 

 ronniere (1957). These may be compared with macrophages (Maral, 1957). 

 It is also apparent in the effect of poliomyelitis on different cell types 

 (Dunnebacke, 1956a,b). 



5. There is a great need for correlative studies of one virus on one cell 

 system by different methods, with concomitant correlations of the amount 

 of virus released with the various cellular lesions as they develop. Presum- 

 ably, this may best be done by simultaneous infections of all cells with a 

 relatively high multiplicity of virus infectious units. Appropriate reference 

 has been made in the text to the few cases where this has been done. More 

 studies which correlate the fluorescent antibody technique with other 

 methods are needed. Coffin and Liu (1957) were able by this technique to 

 identify the specific intracellular localization of distemper virus and to 

 separate this from other cellular lesions. 



6. Tumor viruses have not been shown to differ from other viruses in their 

 localization in the cell or in their intracellular lesions. Virus is found in the 

 cytoplasm, in the microvilli, and within the nucleus in varying degrees. Its 

 association with mitochondria is unsettled, possibly because most of the viral 

 studies have concentrated on the obviously diseased cell, a factor which 

 would unerringly select the cell in which virus and host were out of 

 balance and virus was overcoming host cell. No significant morphological 

 data on the balanced malignant cell produced by virus infection is 

 available. 



