80 F. B. BANG 



studied. One of the difficulties of interpretation is brought out by Morgan 

 et al. (1955), who showed that by serial sections of vaccinia-infected cells "all 

 particles sectioned five or six times can be shown to contain a nucleoid 

 (nucleus) at one stage of development." 



C. Shope Fibroma 



Since this virus has been shown to be related to myxoma and the latter is 

 now included with the poxviruses, some discussion of recent work on this 

 rabbit tumor is appropriate here. Bernhard et al. (1955) have examined by 

 electron microscopy some 13 fibromas and fibrosarcomas provoked by this 

 virus and believe that the virus forms in a homogeneous paranuclear mass 

 within the cytoplasm which they call "viroplasm." The detailed structure of 

 the virus is like the other poxviruses. Febrve et al. (1957) followed the develop- 

 ment of these masses in cell lines originating from rabbit testicles and showed 

 that the diffuse inclusion without identifiable virus units was present as 

 early as 5 hours after infection. This corresponded to the appearance of 

 soluble complement-fixing antigen. Fully developed virus in large amounts 

 was found later. The absence of virus in these inclusions is similar to the 

 ectromelia pathology. 



VII. Herpesvirus 



Although the striking nuclear lesion produced by this virus was early 

 recognized (Cowdry, 1928) and, indeed, has been used to trace the patho- 

 genesis of the disease (Goodpasture and Teague, 1923), our information con- 

 cerning the intracellular pathogenesis of the viral infection is still incomplete. 

 There are no published studies on the microscopic effect of herpesvirus on 

 living cells. A few strains of virus have been studied in the electron micro- 

 scope on a few cell types (Morgan et al., 1954a; Wyckoff et al., 1956). A recent 

 fluorescent antibody study has emphasized the peripheral presence of antigen 

 (O'Dea and Dineen, 1957), although an earlier study has shown virus antigen 

 in the nucleus (Lebrun, 1956). 



A. Intranuclear Inclusion 



The usual description of this lesion includes a separation of the eosino- 

 philic mass from the nuclear membrane and a margination of the chromatin 

 along the membrane. This picture probably represents the last stage in the 

 morphological and chemical breakdown of the integrity of the nucleus 

 (Scott et al., 1953). The somewhat modified picture of the earlier lesion 

 which may be seen in the more adequately fixed chorioallantoic membrane 

 infections (Anderson, 1940; Crouse et al., 1950), may more closely reflect the 

 cellular changes which occur before the cell starts to disintegrate. 



