ANTI-INPECTIOUS SERUM. 489 



Tised in testing tlie genuineness of a suspected Eberth 

 'bacillus. A few hundredths of a c.c. of such serum, in- 

 jected into the peritoneal cavity, will protect a guinea-pig 

 against several tiines the fatal dose of Eberth bacilli, 

 whereas 0.5 c.c. of such serum will not protect against the 

 ■colon bacillus. 



Typhoid fever. — The Eberth bacillus, like the cholera 

 vibrio, colon bacillus, etc., does not give rise to very- 

 poisonous soluble products when grown on ordinary bouillon. 

 A soluble toxin has, however, been recently obtained by 

 cultivating the highly virulent germ on an alkaline medium 

 prepared by digesting the spleen with pepsin. With such a 

 toxin Chantemesse has been able to obtain, although with 

 difficulty, an antitoxic serum. 



When, however, living or dead Eberth bacilli are in- 

 jected subcutaneously or intraperitoneally, a condition of 

 immunity is established' and the serum in this case is anti- 

 infectious. The method of immunizing the guinea-pig or 

 rabbit is essentially the same as that given above under 

 cholera. The serum of a guinea-pig immunized in this way 

 has about the same preventive action as that oi a con- 

 valescent from typhoid fever. The rabbit is more sensitive. 

 The virulence of the Eberth bacilli will vary greatly, thus, 

 some will produce death in a guinea-pig when ^ of a loop- 

 ful is injected into the peritoneal cavity. Usually, however, 

 J - ^ a loopful is necessary. 2-3 loopsf ul of a' culture, which 

 has been killed by exposure to chloroform, or to a tempera- 

 ture of 65°, will be fatal to a 100 g. guinea-pig in 24 hours. 



The defibrinated blood of an animal that has died of 

 an infectious disease may be employed to confer immunity. 

 Thus, Toussaint injected into sheep 3 c.c. of defibrinated 

 anthrax blood, previously heated to 55° 'for 10 minutes, and 

 obtained immunity. The heart-blood of rabbits dead of 

 swine-plague, when heated to 54-58°, will protect rabbits in 



