BACILLUS DIPHTHERIA 519 



is well adapted for the isolation of pseudodiphtheria and xerosis 

 bacilli. 



Pathogenicity. — ^Unlike most other microorganisms, Bacillus diph- 

 therise causes a more or less specific local reaction in mucous mem- 

 branes, which results in the formation of the so-called " pseudo-mem- 

 branes." When these are characteristically present, infection with this 

 bacillus should always be suspected. The consequent disease depends, 

 in part, upon the mechanical disturbance caused by these false mem- 

 branes and, in part, upon the systemic poisoning with the toxin which the 

 bacilli produce. Although the diphtheria bacillus has been found after 

 death in the spleen and liver, we have no data which would justify the 

 assumption that a true diphtheria-septicemia may occur during life. 

 It is probable that in those cases which Baginsky ^ has called the sep- 

 ticemic form of diphtheria, Bacillus diphtherise has merely opened a 

 path by which accompanying streptococci have gained access to the 

 lymphatics and the blood stream. The most frequent sites of diph- 

 theritic inflammation are the mucous membranes of the throat, larynx, 

 and nose. They have also been found in the ear, upon the mucous 

 membrane of the stomach and the vulva, and upon the conjunctiva and 

 the skin. According to Loeffler, Strelitz,^ and others, the bacillus may, 

 by extension from the larynx, give rise to a true diphtheritic broncho- 

 pneumonia. 



For most of the usual laboratory animals the diphtheria bacillus is 

 very pathogenic. Dogs, cats, fowl, rabbits, and guinea-pigs are sus- 

 ceptible. Rats and mice are resistant to all but extremely large doses. 

 False membranes, analogous in every way to those found in human 

 beings, have been produced in many animals of susceptible species, but 

 only after inoculation with the bacillus had been preceded by mechanical 

 injury of the mucosa. The lesions produced in animals by subcutane- 

 ous inoculation present many characteristic features which facilitate the 

 bacteriological recognition of the diphtheria bacillus. Small quantities 

 (0.5 to 1 c.c.) of a virulent broth culture, given subcutaneously to a 

 guinea-pig, may produce the gravest symptoms and within six to eight 

 hours the animal may show signs of great discomfort. Death occurs 

 usually within thirty-six to seventy-two hours. Upon autopsy the point 

 of inoculation is soggy with serosanguineous exudate; neighboring 

 lymph-nodes are edematous. Lungs, liver, spleen, and kidneys are 

 congested. There may be pleuritic and peritoneal exudates. Charac- 



' Baginsky, " Lehrbuch d. Kinderkrankheiten." 

 2 Strelitz, Arch. f. Kinderheilk., 1891. 



