THE CHEMICAL NATURE OF THE 'A'WTTiGE^O, ^B^'AK 

 IN BACILLUS COLI 



Introduction. 



Certain substances when taken into the body paren- 

 terally will cause the production and appearance of 

 protective substances within the body fluids. The pro- 

 tective substances we call antibodies. That which calls 

 forth the production of antibodies is known as antigen. 

 When antigens are allowed to enter into contact with 

 their respective antibodies, either within the animal 

 body or in a test tube, definite changes are observed; 

 thus we have manifestations of these changes in the phe- 

 nomena of agglutination, precipitation, complement fix- 

 ation and other serological reactions. 



But of what do these changes consist? Are they true 

 chemical reactions which follow the usual laws of chemis- 

 try, or are they due to alterations in surface energy and 

 molecular attraction in a physical or physico-chemical 

 sense? And what is the nature, chemically, of the react- 

 ing substances? 



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Most authorities state that all antigens are protein 

 substances. Such statements, as will be shown later, are 

 based to a considerable extent upon prejudice and precon- 

 ceived notions which are not entirely borne out by exact 

 experimental procedure. The substances most generally 

 used as antigens are body fluids (blood serum), body 

 cells, and bacterial bodies. These substances, in the 

 dried state, are composed largely of protein and mineral 

 salts, with a great predominance of the former. Fats and 

 lipoidal material are often present in such small amounts 

 as to escape detection unless large quantities of the 

 native material are used in the analysis. Since the pro- 

 teins seem to be the important constituent of substances 

 used as antigens, and since such substances may be used 

 with equal results after the salts have been removed by 

 dialysis or other method, it was but natural to consider 

 the proteins as antigenic principles. 



A few investigators have endeavored to demonstrate 

 the value of fats and lipoids in serological work. Thus, 

 Jobling and Peterson (1) showed that when bacteria were 

 injected into the blood stream they absorbed lipoidal 

 material which, ordinarily acts as the anti-enzyme con- 

 stituent. Noguchi (2) showed that the tetanolysin frac- 

 tion of the tetanus toxin was neutralized by cholesterin 

 and alcoholic extracts of blood serum. Muller (3) 



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