CONSTITUTION OF COMPLEMENT 



209 



plementoid " (analogous to toxoid). Both complement 

 and complementoid on injection give rise to anti-com- 

 plement. The amount of complement in different sera 

 varies considerably ; horse serum contains very little, 

 guinea-pig serum much, and the complement content of 

 the serum of different individuals of the same species, and 

 even of the same animal at different seasons, varies con- 

 siderably. Complement itself probably consists of two 

 portions, as it is generally accepted that it can be split 

 into a " mid-piece " and an " end-piece " 

 by the action of dilute hydrochloric acid, 

 carbon dioxide, and dialysis. The mid- 

 piece is thought to be in the globulin 

 fraction, the end-piece in the albumin 

 fraction. Noguchi, however, considers 

 that the whole complement is present 

 in the albumin fraction and that inacti- 

 vation of the complement by acid, etc., 

 is due not to splitting into two fractions, 

 but to inactivation of the whole com- 

 plement. 



Pfeiffer's reaction is of considerable 

 value in practical bacteriology for the 

 exact recognition of bacterial species. 



A mixture of a suspension of the 

 organism to be tested with a small 

 quantity of serum from a highly immunised animal is 

 injected into the peritoneal cavity of a normal guinea- 

 pig. The fluid in the peritoneal cavity is then examined 

 microscopically half to one hour after the injection, 

 and if the reaction be positive the organisms will be 

 found in all stages of degeneration, being mostly con- 

 verted into spherules. In this case, the organism is to 

 be regarded as being identical with the organism by 

 means of which the immune serum used in the test was 



14 



FIG. 33. Diagram 

 to show the union 

 between comple- 

 ment (black) and 

 protoplasm of the 

 cell by means of 

 the amboceptor 

 (white). (After 

 Ehrlich.) 



M.B. 



