294 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



duced as a result of the immunization and present only in 

 the blood of immunized animals; the other a normal con- 

 stituent of blood serum common to the blood of most, if not 

 all, species of animals. The substance produced as a result 

 of the immunization, that is, the specific antibody, has been 

 termed the amboceptor. The substance present normally 

 in the blood serum of most animals is termed the comple- 

 ment. Cytolysin, therefore, is amboceptor plus comple- 

 ment. 



Experiment has shown that amboceptors are highly 

 specific. They unite only with the kinds of cells instru- 

 mental in causing their production. It may be shown 

 experimentally that whenever amboceptor comes in contact 

 with its specific antigen, the two unite. There is, however, 

 no visible change of any kind. If complement is then 

 added, it in turn unites with the antigen and brings about 

 the hemolysis. The amboceptor, in other words, is a spe- 

 cific substance which sensitizes bacteria or other cells to the 

 action of a universally present complement. Thi& may be 

 shown by mixing a heated antiserum, that is, a serum con- 

 taining cytolysin in which the complement has been 

 destroyed by heat (leaving the amboceptor only) with suit- 

 able cells, allowing them to stand in contact for a time, then 

 washing repeatedly (by means of the centrifuge) in physio- 

 logical salt solution. Cells treated in this fashion 

 brought into contact with serum containing complements 

 will be rapidly destroyed. Neither the heated serum alone, 

 containing amboceptor, nor the normal serum alone, con- 

 taining complement, is able to destroy the cells, but when 

 the cells are sensitized by the presence of amboceptors, the 

 complement is capable of destroying them. 



It is apparent that immunity to many diseases is due, at 

 least in part, to the production of these specific amboceptors 

 in the blood. Such amboceptors, for example, may be 

 demonstrated in the blood serum of a person who has recov- 



