362 S. GARD AND O. MAAL0E 



Oster (1947) has analyzed the effects of ultrasound on TMV by following 

 the changes in birefringence, viscosity, size distribution, as well as the loss of 

 infectivity. From the size distribution at various times he concluded that the 

 2800 A virus rod is fractured near its center and that the smaller pieces are 

 broken in the same way to give fragments about I and I of the original rod. 

 The preferential breaking of the rods into halves is presumably due to maxi- 

 mum hydrodynamic stress occurring near the center, and need not imply the 

 existence of weak points in the biological structure of these particles. It is an 

 interesting consequence of this observation that the fraction of particles not 

 yet broken should decrease exponentially with time of treatment, whereas 

 the frequencies with which pieces one-half or less the length of the original 

 rod occur should increase before beginning to drop. Since the infectivity of 

 the preparations is observed to decrease exponentially, it seems justifiable to 

 conclude that only the 2800 A rods possess infectivity (the same conclusion 

 has been reached independently on the basis of X-ray experiments; see 

 p. 371). 



Oster also observed that longitudinal aggregation of the TMV fragments 

 did not result in reactivation; this also suggests that the virus rod constitutes 

 an organized unit the fragments of which cannot be effectively reassembled 

 by random aggregation. 



Malkiel (1947), studying similar fragments serologically, has shown that 

 their capacity for combining with antibody molecules is strikingly increased. 

 No new antigens seem to be uncovered by the sonic treatment. 



The work of Newton (1951) with high-intensity sound waves extends 

 Oster's observation. Despite very complete fragmentation of the virus rods 

 there appeared to be no denaturation of the antigens. Later, Newton and 

 Kissel (1953) carefully analyzed the size distribution after various intensities 

 of sonic treatment; they concluded that the virus rod may have a weak point 

 at a distance of about 1000 A from one end. 



An extensive study by Rheins and Finlay (1954) on various preparations 

 of influenza virus showed that highly purified virus is much more susceptible 

 than are the particles in chorioallantoic fluid. Appreciable inactivation was 

 observed if the temperature was allowed to rise to about 50°C., but not if 

 the temperature was kept below 30°C. during treatment. The antigenic and 

 hemagglutinating capacity of the virus remained unimpaired even when in- 

 fectivity had been greatly reduced. The sonic treatment furthermore proved 

 very effective in releasing virus from allantoic membranes, and the authors 

 discuss the practicability of using large-scale sonic treatment as a means of 

 improving the quality and the yield in vaccine production. 



The tests carried out with other animal viruses are largely qualitative. 

 Partial inactivation has been demonstrated for vaccinia (Yaoi and Nakahara, 

 1934; Rivers et al., 1937) and polioviruses (Kasahara and Ogata, 1938; 



