126 ESSENTIALS OF BACTERIOLOGY 



In rabbits 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 manner, 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 without themselves becoming infected. 



Prevalence of Bacillus Diphtheria. Examinations made on 

 a large scale of the throats of supposedly healthy individuals 



Fig. 64. Bacillus diphtheriae, from a pure culture. 



have shown that the Bacillus diphtheriae is rather widely dis- 

 tributed. Not only does it linger for many weeks in the throats 

 of persons recently recovered from the disease, but it is found 

 in the care-takers, nurses, etc., and there are allied organisms, 

 with more or less pathogenicity, that have been found in 

 atrophic rhinitis, in conjunctivitis, and in the throats of 

 unexposed normal individuals. The pseudobacillus of Hoff- 

 man is believed by many investigators to be but a weakened 

 diphtheria bacillus that has lost its toxic power. 



Methods of Diagnosis. A small piece of exudate or some 

 secretion from pharynx, tonsil, or nares is obtained on a sterile 

 cotton swab and transferred, as soon as possible, to the surface 



