78 II. FUNDAMENTAL STRUCTURE OF PROTOPLASM 



mostly of tailless elements though often a small number of tailed par- 

 ticles were contained. The tailless particles would not be adsorbed 

 by phage sensitive bacteria. This shows that in these particles the 

 virus pattern was either absent or incomplete. The presence of tail 

 may indicate the existence of complete virus pattern. An evidence 

 was shown to suggest that nucleic acid content, if any, in these tail- 

 less incomplete particles was much lower than that of complete active 

 particles. The tail formation may thus be attributed to high nucleic 

 acid content which may render some elementary bundle unable to 

 shrink. 



As is well known, tailed particles are never confined to phage. 

 For example, Newcastle disease viruses sometimes prove to have a 

 tail, though more occasionally they are found in filamentous forms, 

 which are believed by the writer to be elementary bundles or elemen- 

 tarj^ bodies in an unfolded state. If some elementary bundle was left 

 in this unfolded state, whilst the others formed a coagulated body on 

 folding or shrinking, a tail would be produced as in the case of phage. 

 According to Bang (68) Newcastle disease virus becomes filamentous 

 when brought into hypertonic solutions of sodium chloride, whilst 

 becomes spherical in water or 0.8 per cent salt solution. It is worthy 

 of note that this change is reversible ; no loss of infectivity is detected 

 during the change. 



Poliomyelitis virus m.ay present another example : Bourdillon (69) 

 claimed that electron micrographs of this virus show filaments of 

 15m/j. wide, purified preparations readily agglutinating lineally and 

 showing anisotropy of flow. In these and other respects they resem- 

 ble closely some plant virus preparations, though filaments of animal 

 viruses seem far more tender than those of plant viruses, a fact which 

 may chiefly be attributed to the presence of lipids. There are also 

 many reports informing of the filamentous forms of influenza virus. 

 Avian erythromyeloblastic leucosis virus is likewise stated to be some- 

 times tailed particles (70). Studies of dengue fever virus by electron 

 mircoscope has shown that the virus is thread-like particles, 42 to 

 46 m// in width and 175 to 220 m/z in length (71). 



Filaments of viruses such as those of Newcastle disease and 

 polyomyelitis may be the unfolded elementary bundles or their end-to- 

 end association products, since their width is reported to be similar to 

 that of tobacco-mosaic virus, whereas, in some cases at least, this does 

 not seem to hold for influenza virus, because electron micrographs 

 of influenza virus show that the filaments are far thicker in width 

 than those of the former viruses, seggesting that the filaments of 

 influenza virus are the elementary bodies themselves coagulated in 

 forming a thread by end-to-end association. Actually many workers 



