II. THE SIZE OF VIRUS PARTICLES 



13 



pass through 0.34 ij. membrane was calculated from the experimental 

 results indicated in Table 1, and estimated to be about 50-100 : 1. On 

 the assumption that the average size was proportional to the pore 

 diameter of the membrane, and that the larger particles were larger 

 than the smaller ones by 1.5x1.5, the calculation was made as follows: 



The activity of the larger-particle phage for a single particle : 



the activity of the smaller-particle phage for a single particle 



= (100-45) X (1.5x1.5)7(100-84) : 3/9.5 = 100 : 1. 



This was obtained from the data of phage II in the Table, while 

 from the data of phage I it was calculated as 50 : 1. This showed 

 that the ratio of the number of the active large particles to the total 

 number of the large-sized particles was about 50-100 times as great as 

 the radio calculated with the small-sized particles. This may be at- 

 tributed to the labile property of the small sized particles; as shown in 



Table 2 



Relation between the Size of Phage Protein Partice and Its Resi- 

 stance to Heat 



Table 2, the resistance of phage to heat varied remarkably with the 

 particle size, and the larger the size the greater the resistance ; in 

 other words, phage protein existing in a larger particle was more stable 

 to heat than that in a smaller particle, showing that the property of 

 the phage protein varied with particle size. 



As described already, viruses are considered to have the faculty to 

 cause a structural change in the protoplasm protein, thereby the pro- 

 tein can acquire the virus function. If the protein coagulates into too 

 small particles on such a change, active structures in the particle may 

 be labile and readily inactivated. There is a good reason, as will be 

 described in a later chapter, to assume that virus protein has to exist 



