1913] Charles Frederick Bolduan 251 



It has been found that this action may be developed against cells 

 other than bacteria. When red blood cells are used for the injec- 

 tions, the serum acquires dissolving properties for these ; and here 

 again the action is strictly specific, so that when blood cells from a 

 chicken are injected into an animal, the serum of the injected animal 

 acquires increased solvent powers only for chicken blood cells, not 

 for blood cells of other animals. Sera directed against blood cells 

 are usually spoken of as hemolysins. The term cytolysin is used to 

 embrace all these cell-dissolving sera. 



Complement and immune body. Investigation has shown that 

 the mode of action of these dissolving sera is somewhat complex, 

 and consists of the Joint action of two substances. It may be re- 

 called that this dissolving action was observed in fresli serum. 

 Serum which had stood for several days no longer possessed this 

 property. The researches of Metchnikoff and Bordet showed that 

 the füll solvent power could be restored by the addition of a little 

 fresh serum, even from a normal, untreated animal. Evidently, 

 then, of the two substances concerned in this dissolving action, one 

 is quite stable, and the other highly labile. The labile substance, 

 derived from a normal untreated animal, is spoken of as the com- 

 plement; it is not specific. The stable substance, present only in 

 the serum of the treated animal, is called the immune body; it is 

 highly specific. When an animal is repeatedly injected with grad- 

 ually increasing doses of bacteria, or other cells, it responds by man- 

 ufacturing large quantities of this "immune body" directed spe- 

 cifically against the injected cells. The complement is not increased 

 in the process. 



Agglutinins. When the serum of an animal which has been 

 repeatedly injected with gradually increasing doses of bacteria is 

 brought into contact with some of the bacteria, careful Observation 

 under the microscope reveals a very interesting series of changes. 

 Thus, if typhoid bacilli are mixed with a specific antityphoid serum 

 (obtained, let us say, from a rabbit previously injected with typhoid 

 bacilli), one notices, first, that the motility of the bacilli becomes 

 markedly diminished. This is followed by the gradual collection 

 of the bacilli into clumps. At the end of an hour or two, in place 

 of countless bacteria moving quickly through the field, one sees 



