Bacillus Pyocyaneus 271 



in some cases to a deep reddish-brown color. This pig- 

 ment has been made the subject of a careful investigation 

 by Jordan.* 



A well-known feature of the growth upon fresh agar- 

 agar, upon which much stress has recently been laid by 

 Martin, f is the formation of crystals in fresh cultures. 

 Crystal-formation in cultures of other bacteria usually takes 

 place in old, partially dried agar-agar cultures, but Bacil- 

 lus pyocyaneus often produces crystals in a few days upon 

 fresh media. In my experience freshly isolated bacilli show 

 this power more markedly than those which have been for 

 some time part of the laboratory stock of cultures and 

 frequently transplanted. 



Bouillon. In bouillon the organism produces a diffuse 

 cloudiness, a fluorescence, and sometimes an indefinite thin 

 pellicle on the surface. 



Potato. Upon potato a luxuriant greenish or brownish, 

 smeary layer is produced. 



Milk. Milk is coagulated and peptonized. It is slightly 

 acid for the first day or two, then becomes alkaline again. 



Pathogenesis. The bacillus is pathogenic for the small 

 laboratory animals, but different cultures differ greatly 

 in virulence, i c.c. of a virulent bouillon culture, injected 

 into the subcutaneous tissue of a guinea-pig or a rabbit, 

 causing rapid edema, suppurative inflammation, and death 

 in a short time (twenty-four hours) . Sometimes the animal 

 lives for a week or more, then dies. There is a marked 

 hemorrhagic subcutaneous edema at the seat of inoculation. 

 The bacilli can be found in the blood and in most of the 

 tissues. 



Doses too small to prove fatal sometimes lead to suppu- 

 ration, and the injection of sterilized cultures leads to simi- 

 lar results, a relatively larger quantity being required. 



Intraperitoneal injections cause purulent peritonitis. 



Blum J reports a case of pyocyaneus infection with endo- 

 carditis in a child. 



Lartigau, in his study of "The Bacillus Pyocyaneus as 

 a Factor in Human Pathology," sums up what is known 

 about this role of the organism as follows: "The Bacillus 

 pyocyaneus, like many pathogenic micro-organisms, is 



*" Journal of Experimental Medicine," vol. iv, 1899. 

 f'Centralbl. f. Bakt.," xxi, April 6, 1897, p. 473. 

 t " Centralbl. f. Bakt. u. Parasitenk.," Feb. 10, 1899, xxv, No. 4. 

 "Phila. Med. Jour.," Sept. 17, 1898. 



