PATHOGENIC BACTERIA. 113 



Pathogencsis. By inoculation, animals, which naturally are 

 not subject to diphtheria, have had diphtheritic processes de- 

 velop at the site of infection ; hemorrhagic oedema then follows, 

 and death. 



In rabhits paralyses develop, and when the inoculation occurs 

 upon the trachea, all the prominent symptoms of diphtheria 

 show themselves. 



Manner of Infection in Man. The exact way is not yet known. 

 It is supposed that the mucous membrane altered in some man- 

 ner, the diphtheria bacillus, then gains entrance and the disease 

 develops. The bacilli may be found in healthy individuals who 

 may act as a source of infection to susceptible individuals with- 

 out themselves becoming infected. 



Products. But it is not the mere presence of the bacillus that 

 gives rise to all trouble ; certain products which they generate 

 get into the system and produce the severe constitutional symp- 

 toms. 



Koux and Yersin, in 1888, discovered that the injection of the 

 filtered culture bouillon (that is, freed of all diphtheria bacilli) 

 gave rise to the same palsies as when the bacilli themselves were 

 introduced. 



Toxins of Diphtheria. Brieger and Frankel filter the bouillon 

 culture, evaporate (in vacuo at 27 C.) to volume, then treat 

 with 10 volumes of alcohol and acetic acid, the precipitate re- 

 dissolved in water and reprecipitated with the acidulated alco- 

 hol until a clear aqueous solution is obtained ; this is then 

 dialyzed for 72 hours, and again precipitated with alcohol, and 

 dried ; a white amorphous body results, giving all the reactions 

 of an albumen, and called by them toxalbumen. 



The toxin of diphtheria, first demonstrated by Roux and 

 Yersin, is not an albumen. It is obtained by growing virulent 

 bacilli in bouillon for three or four weeks at 37 C. After a 

 sufficient alkalinity has been produced the cultures are fil- 

 tered, and the filtrate should have a toxicity that will destroy 

 a 500-gramme guinea-pig in twenty-four hours when 0.1 c. cm. 

 of the toxin is injected. 



Antitoxin. Bearing found that animals rendered immune 



