50 II. FUNDAMENTAL STRUCTURE OF PROTOPLASM 



more probable explanation that most of the small-sized particles cannot 

 act as the virus because of the low polymerization degree. Phage 

 particles of extremely small sizes were occasionally found to produce 

 only very small plaques showing their weak activity. 



In the studies on the interaction of large and small haemoaggluti- 

 nating particles of Newcastle disease virus with red cells, Grenoff and 

 Henle (15 a) have found that whereas large particles were readily ad- 

 sorbed onto red cells, only relatively small amounts of small particles 

 appear to combine with red cells under the same conditions, and more- 

 over, large particles cause haemolysis whereas small ones lack this 

 property. 



It is well known that antigenic substances are always large mole- 

 cules, of molecular weight of the order of 10,000 or more, and conse- 

 quently being usually colloidal in solution. This shows that, in order 

 to act as antigens, antigenic substances must be in molecular state of 

 considerable sizes as in viruses, although the sizes required for antigens 

 are not so large as those of the viruses. Polysaccharides isolated from 

 bacteria are generally non-antigenic, but when adsorbed on particulate 

 substances, such as collodion particles or kaolin, they can act as anti- 

 gens. Again, albumose, though usually non-antigenic, can produce 

 antibody if adsorbed on colloidal aluminium hydroxide. Also some 

 lipids extracted from various organisms are not antigenic per se, but 

 when injected into an animal after mixed with swine serum, can cause 

 the antibody production. 



These non-antigenic substances may acquire the antigen-ability by 

 the polymerization on the surface of colloidal particles on which they 

 are adsorbed, thereby the physicochemical force capable of acting as 

 the active group of antigens may become greater. They may possibly 

 act as antigens even when no such polymerization occurs, if non-specific 

 colloidal particles injected with them can induce some disturbances in 

 the protoplasm configuration of the antibody-forming cell, on which the 

 mixtures or complexes are adsorbed, in assisting the formation of the 

 replica corresponding to the antigenic pattern in the protoplasm. In 

 the opinion of the writer antigens like viruses act as templates to 

 produce replicas in the protoplasm (22). There are many evidences 

 that a non-specific disturbance in the protoplasm caused by factors 

 other than viruses may exert a favourable influence upon a virus to 

 infect the cell ; a detailed account of this will be given later. 



Enzymes are another agent for whose function a similar large 

 molecular state may be necessary. A group of enzymes, known as 

 conjugated ones, consists of two components, /. e. coenzyme and apo- 

 enzyme ; the former in itself has no enzymatic action and has a low 

 molecular weight, but on combination with the latter the activity of the 



