176 A MANUAL OF BACTERIOLOGY 



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 inactivation of the complement 

 by acid, etc., is due not to splitting into two fractions, but 

 to inactivation of the whole complement. 



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 converted into 

 spherules. In this case, according to Pfeiffer, the organism 

 is to be regarded as belonging to the same species as that 

 by means of which the immunisation of the animal, from 

 which the blood-serum was obtained, was carried out. If, 

 on the other hand, the reaction be negative, the organisms 

 are unaffected after being in the peritoneal cavity for an 

 hour or so, and the organism is then considered to be a 

 species different from that used for the immunisation. 

 Thus, Pfeiffer's reaction may be made use of to differentiate 

 the cholera-like vibrios from true cholera vibrios and the 

 members of the typhoid- colon group from one another. 



The destruction of the bacteria by bacteriolysis is 

 regarded by some as being brought about by osmotic 

 changes, by others by processes analogous to digestion. 

 During bacteriolysis the specific immunising substances 

 and anti-bodies are used up, and for the lysis of a given 

 quantity of bacteria a certain amount of immune serum 



