BACILLUS DIPHTHERIA 519 



found in the car, upon the mucous membrane of the stomach and the 

 valva, and upon the conjunctiva and the skin. According to Loeffler, 

 Strelitz, 1 and others, the bacillus may, by extension from the larynx, 

 give rise to a true diphtheritic broncho-pneumonia. 



For the usual laboratory animals the diphtheria bacillus is very 

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

 Rats and mice are resistant. False membranes, analogous to those 

 found in human beings, have been produced in many animals, but 

 only when inoculation had been preceded by mechanical injury of the 

 mucosa. Small quantities (0.5 to 1 c.c.) of a virulent broth culture, 

 given subcutaneously to a guinea-pig, may produce the gravest symp- 

 toms 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 serosan- 

 guineous exudate; neighboring lymph-nodes are edematous. Lungs, 

 liver, spleen, and kidneys are congested. There may be pleuritic and 

 peritoneal exudates. Pathognomonic is a severe congestion of both 

 suprarenal bodies. The gastric ulceration recently described by Rose- 

 nau and Anderson 2 may occur, but are by no means regularly found 

 (two out of fifty in our series 3 ). 



Determination of Virulence. When diphtheria or diphtheria-like 

 bacilli are isolated from the throats of patients not showing typical 

 clinical diphtheria, or from healthy individuals suspected of being 

 carriers, it is important to determine whether these organisms are viru- 

 lent. The usual criterion is their virulence for guinea-pigs. Two c.c. 

 of a forty-eight-hour broth or ascitic broth culture are injected sub- 

 cutaneously into a normal guinea-pig. This dose will kill the pig in 

 three to five days if the culture is virulent. A control injection should 

 always be made into another pig of the same weight, which has 

 previously received an injection of antitoxin (at least 250 units). 

 Recently Neisser has suggested that the intracutaneous injection of 

 the suspected bacilli may be used for the determination of virulence. 

 This has the advantage of economy, as several tests can be carried 

 out on the same pig. The method as applied by Zingher and Soletsky * 

 has been to use the following modification of Neisser 's method: Two 

 guinea-pigs of about 250 gr. are used for the test. The abdominal 



1 Strelitz, Arch. f. Kinderheilk., 1891. 



2 Rosenau and Anderson, Jour. Inf. Dis., iv, 1907. 



3 Zinsser, Journ. Med. Res., xvii, 1907. 



* Zingher and Soletsky, Jour. Inf. Dis., 1916, xvii, 54. 



