V. FINER STRUCTURE OF VIRUS PARTICLES AND ITS SIGNIFICANCE 69 



of such a structure may be achieved by a basic physicochemical pro- 

 perty belonging naturally to the protoplasm protein. The writer was 

 actually able to confirm in vitro that some plant protein of globulin 

 nature does possess the property of forming virus-like particles. 

 According to his investigation, no particulate protein was contained iri 

 Merck's ricin preparation, but when its water solution was added 

 with ethanol at 30 per cent, its pH being adjusted to 5.5 by the addi- 

 tion of acetic acid, and left in an ice box for several days, then the 

 protein molecules in the preparation together with some lipids sedi- 

 mented in forming virus-like particles ; these particles would further 

 unite with one another to form homogeneous protoplasm-like body, if 

 they were left at laboratory temperature after being isolated from tlie 

 original solution by centrifugation and subsequently suspended in a 

 weakly acid solution at the isoelectric point. When pressed mechani- 

 cally or added with alkali, the homogeneous protoplasm-like body thus 

 formed would be decomposed again into virus-like particles (51). 



This important finding strongly suggests that at least some pro- 

 teins with globulin nature possess a basic character to polymerize into 

 virus-like particles, which in turn tend of fuse into a protoplasm-like 

 body. But since the association among the particles in such a body 

 may not be firm enough, the body may be disposed to disintegrate 

 again into the particles. Elementary bodies and the protoplasm can 

 be regarded as such particles and the body, respectively. Since this 

 fact is the utmost important and the most fundamental, on the basis 

 of which the writer's theory as regards the protoplasm structure have 

 been developed, we shall have occasion later to discuss more in detail 

 on this subject. 



Svedberg and Pederson (52) postulated the term proteon to designate 

 a native protein unit incapable of dividing into still smaller units 

 having the native protein character. According to them, every native 

 protein may be regarded as a system of such proteons. The concep- 

 tion, that a protein particle is not a mere conglomerate of proteons but 

 an orderly aggregate or a polymerization, arose from their finding that 

 in many cases, where ultracentrifugal studies show that a protein is 

 uniform in size and shape under well defined external conditions, the 

 protein in question is capable ol dissociating into subunits when the 

 environmental conditions are modified. It may perhaps be permissible 

 to say, that the formation of a virus-like particle or its decomposition 

 into unit molecules is only the manifestation of one of the basic 

 characters of proteins. 



Whereas haemocyanin has long been regarded as one of the best 

 examples of dissociable complex, Brohult (53) found that its depolyme- 

 rization is a function of both pH and salt concentration, the depolyme- 



