IMMUNOLOGY AND SELF-SAVING CATALYSTS 145 



particles {e.g., bacteria, red blood cells) is mixed with a serum con- 

 taining the specific antibody elicited by injections, the particulate 

 antigen agglutinates, or forms floes which usually settle out. Motile 

 antigen cells, such as typhoid bacteria or sperms, lose their inde- 

 pendent motility on coherence, though some cells in a floe may 

 show some motion for a while. This is seen in the Widal test for 

 typhoid fever, for in the serum of a person who has, or has recently 

 recovered from the disease, live, motile typhoid bacilli agglutinate 

 and soon dissolve — the phenomenon termed lysis (solution). 



(4) Lysis: Antibodies that can dissolve or disintegrate a par- 

 ticulate antigen are termed lysins. Special names indicate the kind 

 of antigen dissolved: bacteriolysis, for bacteria; cytolysis, for cells; 

 hemolysis, for blood corpuscles. 



Complement or Alexin 



After 15 minutes' heating at 55° C an immune serum capable of 

 causing lysis of cholera vibrios loses this power, but regains it on 

 the addition of some unheated non-immune serum. Obviously, 

 both immune and non-immune sera contain a factor essential to 

 the action of the lysin. Prof. Jules Bordet of the University of 

 Brussels (Nobel prize 1922) termed this factor alexin (from the 

 Greek meaning helper), while Prof. Paul Ehrlich of the University 

 of Berlin (Nobel prize 1908) called it complement. In the Wasser- 

 mann test a normal serum furnishes the proper amount of com- 

 plement, so that complete lysis occurs. With the serum of a person 

 having syphilis, the complement is altered, bound, or "deviated" to 

 a greater or less extent, so that lysis takes place only partially or not 

 at all. Absence of lysis is recorded on an arbitrary scale as 4 + . 



Antibody Formation 



Though antibodies are usually tested for in body fluids such as 

 blood serum and spinal fluid, it is believed that they are formed 

 within the cells. On bleeding an immunized animal, for example 

 a horse, to extract diphtheria antitoxin, a new supply is con- 

 tinuously forthcoming. Since a small amount of antigen can pro- 

 duce an indefinitely large amount of specific antibody, it is obvious 

 that the original antigen molecules cannot constitute the antibody, 

 even in part. This led me to the view that the antigen formed a 

 specific catalyst surface or template, against which a specific anti- 

 body of opposite contour could be molded. I have illustrated this 

 notion in frequent private discussions and public lectures, by 



