IV. THE CRYSTALLINITY OF VIRUSES 59 



to stand for a long period, disappeared gradually in fusing homogene- 

 ously. 



These facts may be interpreted as flollows: Plant elementary bodies 

 which have been coagulated in the course of isolating procedure can 

 solve the coagulation, when stand at the isoelectric point, in liberating 

 the polar groups which subsequently can make the particles associate 

 with one another to form large masses which may be looked upon as 

 the protoplasm itself. In other words, the coagulated elementary bodies 

 can solve the coagulation to unite with one another, thereby they may 

 be arranged orderly as in the original protoplasm, thus recovering the 

 structure of the protoplasm itself. Therefore, the fusion of particles 

 to larger bodies may be regarded as their return to the original proto- 

 plasm mass. At the isoelectric point COOH groups of the protein can 

 coexist with the NH3 groups, probably contributing to the fusion of the 

 particles. 



The fact that such fusion can take place with plant particles, 

 whereas this is not the case with animal ones, suggests that plant 

 particles can readily solve their coagulation and can combine with one 

 another while animal particles fail to do so. On the other hand, this 

 may account for the difficulty of plant protoplasm to be coagulated into 

 minute particles. Whereas animal particles can readily be precipitated 

 only by the shift of the pH to its isoelectric point, plant particles oc- 

 casionally fail to be obtained by this process ; the addition of salts such 

 as ammonium sulphate or sodium chloride is required for the complete 

 precipitation. Thus, in the case of plant materials, mechanical grind 

 may not be sufficient for the coagulation of elementary bodies. It is 

 actually known that plant virus particles such as those of tomato bushy 

 stunt, tobacco necrosis, southern bean mosaic and turnip yellow mosaic 

 are soluble even at the isoelectric point and fail to precipitate (25). 



2. The Expulsion of Lipids 



The property of plant particles to fuse into homogeneous masses 

 may be closely related to their crystallinity. Homogeneous masses 

 appear sometimes as if they were crystals, but if produced by the 

 mere addition of acetic acid, they never proved to be optically aniso- 

 tropic when observed through crossed Nicol prisms, whereas precipitates 

 with double refraction were sometimes formed when ammonium sulphate 

 at 1 '3 saturation was added together with acetic acid ; that is, crystals 

 were formed when ammonium sulphate was added. 



Among the plants serving as our experim.ental materials, the doubly 

 refracting property was most distinctly observed with precipitates ob- 



