BACILLUS PYOCYAM-US 375 



gelatin is usually all liquefied. The deep colonies, before liquefaction 

 sets in, appear as round, granular masses with scalloped mari:in>, 

 having a yellowish-green color; the surface colonies have a darker 

 green centre, surrounded by a delicate, radiating zone. In stick cul- 

 ture* in gelatin liquefaction occurs at first near the surface, in the form 

 of a small funnel, and gradually extends downward; later the liquefied 

 gelatin is separated from the solid part of the medium by a horizontal 

 plane, a greenish-yellow color being imparted to that portion which 

 is in contact with the air. On agar a wrinkled, moist, greenish-white 

 layer is developed, while the surrounding medium is bright green; 

 tli is subsequently becomes darker in color, changing to blue-green 

 or almost black. In bouillon the green color is produced, and the 

 growth appears as a delicate, flocculent sediment. Milk is coagulated 

 with coincident acid reaction. 



There is some difference of opinion in regard to the pigments 

 produced by the bacillus pyocyaneus. Gessard's view is that two pig- 

 ments are produced by this bacillus one of a fluorescent green and 

 the other (pyocyanin) of a blue color. Pyocyanin is soluble in chloro- 

 form, and may be obtained from pure solution in long, blue needles. 

 The pigment which is thus extracted by chloroform distinguishes the 

 bacillus pyocyaneus from other fluorescing bacteria. 



Distribution. This bacillus is very widely distributed in nature; 

 it is found on the healthy skin of man, in the feces of many animals, in 

 water contaminated by animal or human material, in purulent dis- 

 charges, and in serous wound secretions. 



Pathogenesis. Its presence in wounds greatly delays the process 

 of repair, and may give rise to a general depression of the vital powers 

 from the absorption of its toxic products. Its pathogenic effects on 

 animals have been carefully studied. It is pathogenic for guinea-pigs 

 and rabbits. Subcutaneous or intraperitoneal injections of 1 c.c. or 

 more of a bouillon culture usually cause the death of the animal in from 

 twenty-four to thirty-six hours. Subcutaneous inoculations produce 

 an extensive inflammatory oedema and purulent infiltration of the 

 tissues; a serofibrinous or purulent peritonitis is induced by the intro- 

 duction of the bacillus into the peritoneal cavity. The bacilli multiply 

 in the body, and may be found in the serous or purulent fluid in the 

 subcutaneous tissues or abdominal cavity, as well as in the blood and 

 various organs. When smaller quantities are injected subcutaneously 

 the animal usually recovers, only a local inflammatory reaction being 

 set up (abscess), and it is subsequently immune against a second inocu- 

 lation with doses which would prove fatal to an unprotected animal. 

 It is interesting to note that Bouchard, Charrin, and GuigBJlld have 

 shown that in rabbits which have been inoculated with a culture of 

 the bacillus anthracis a fatal result may be prevented by inoculating 

 the same animal soon after with a pure culture of the bacillus pyo- 

 cyaneus. Loew and Emmerich have shown that the en/ymes pro- 

 duced in the pyocyaneus cultures are capable of destroying many 

 forms of bacteria in the test-tube, and have a slight protecting value in 



