X. THE CHANGE OF PROTOPLASM STRUCTURE 303 



on the protein would be expected to favour the absorption of the 

 sodium cation. Modification of the albumin by treatments which 

 weaken the basic groups generally decreases the adsorbing properties, 

 and it is generally accepted that the preference which albumin shows 

 for anions is connected with the activities of the lysine and arginine 

 residues, both of which possess single positive charges at physiologi- 

 cal pH (136). 



In the customary consideration of the absorption mechanism the 

 existence of the so-called semipermeable membrane seems to be essen- 

 tial. The membrane is believed by some workers to be present even 

 in viruses. For example, sedimentation of virus particles in sola 

 tions of low molecular weight, such as sucrose, sodium chloride, and 

 glycerol, has revealed a dependence of sedimentation rate on solute 

 concentration, and further the rate was found to vary with time of 

 contact with the solute. These facts seem to be often interpreted 

 as giving evidences of the existence of a semipermeable membrane 

 susceptible to osmotic effects of solutes of low molecular weight (137). 

 However, these facts should be accounted for by the change in the 

 rate of "absorption" responding to the concentration of the substances 

 to be absorbed and responding to the time of contact. Membrane-like 

 images shown in electron micrographs of some viruses may, as already 

 pointed out, be interpreted as only an artificial product produced by the 

 surface-protein molecules fused into a membrane-like aggregate through 

 the heat of electron bombardment. 



Bergold and Wellington (138) claimed that they could isolate from 

 certain insect-virus particles particulate protein complex without DNA, 

 which they believed to be the membrane of the virus. However, it is 

 possible that this "membrane" may be the particles, which contain no 

 DNA, contaminating the "virus particles" that contain a large amount 

 of DNA. Insect virus particles were separated from inclusion bodies 

 which had been formed in the insect after the virus infection. Ac- 

 cording to Bergold (139) the inclusion bodies consisted of about 95 per 

 cent of a homogeneous protein and about 3-5 per cent of virus particles; 

 these virus particles which contained DNA in rich amount could be 

 liberated by dissolution of the inclusion bodies in weak alkali and 

 separated from other component proteins by centrifugation. This fact 

 suggests that the "virus particles" were the DNA rich elementary 

 bodies which could withstand the alkali treatment owing to their 

 high contents of DNA ; the other component bodies might be decom- 

 posed and dissolved in the alkali so that virus activity might be left 

 only in the undissolved particles containing DNA. It should be noted 

 that the "membrane" was reported to dissolve in alkali like the main 

 component protein of the inclusion body, suggesting thus strongly that 



