MACROMOLECULES 39 



plant sap. With which system the influenza virus is more comparable 

 remains to be determined, for there is no evidence to show whether the 

 serologically active material ever develops into infective particles, 

 either by subsequent assembly or by the removal of inhibiting 

 materials. 



To many virus workers, the infective particles may seem the only 

 important ones, and it is understandable that most work has so far been 

 directed towards obtaining apparently homogeneous preparations with 

 the highest infectivity. Nevertheless it would be a mistake to focus 

 attention exclusively on the infective particles or to place too much 

 reliance on physico-chemical and serological tests as indicating biological 

 uniformity. Already, it is obviously misleading to assume, as is com- 

 monly done, that any anomalous particles which can be sedimented 

 from infective extracts in the ultracentrifuge or resolved by the electron 

 microscope, are necessarily capable of infecting a new host. Many 

 such particles, although specific to infected cells, are non-infective, and 

 whether they represent intermediate stages in the synthesis of infective 

 particles, degradation products, or complexes with host constituents, 

 their further study can hardly fail to illuminate the complex processes 

 that proceed in virus-infected cells. 



LITERATURE CITED 

 Bawden, F. C. and Pirie, N. W. (1945a). Brit. J. Exp. Path., 26, 277. 

 Bawden, F. C. and Pirie, N. W. (1945b). Brit. J. Exp. Path., 26, 294. 

 Bawden, F. C. and Pirie, N. W. (1950). J. Gen. Microbiol., 4, (in press). 

 Hoyle, L. (1948) Brit. J. Exp. Path., 29, 390. 

 Markhara, R. and Smith, K. M. (1949). Parasitology, 59, 330. 

 Miller, G. L. and Stanley, W. M. (1942). J. Biol. Chem., 146, 331. 

 Oster, G. (1947). /. Gen. Physiol., 51, 89. 

 Schramm, G. and Miiller, H. (1940). Z. Physiol. Chem., 266, 43. 



