164 ESSENTIALS OF BACTERIOLOGY 



faction, and appearing, under low power, when still young, as 

 yellowish green, the periphery being granulated. 



On agar: A bright green at first, causing fluorescence; then 

 later a blue pigment. 



Stab-cultures. Mainly in upper strata, the liquefaction 

 funnel shaped, the growth gradually settling at the bottom, a 

 rich green shimmer forming on the surface, and the gelatin 

 having a deep fluorescence. 



Potato. The potato is soaked with the pigment, a deep fold 

 of green occurring on the surface. 



Fig. 99. Koch-Weeks' bacillus from cpnjunctival exudate at third day of 

 epidemic conjunctivitis (Boston). 



Staining. With ordinary anilin dyes. 



Pathogenesis. When animals are injected with fresh cultures 

 in the peritoneal cavities or cellular tissues, a rapidly spreading 

 edema with general suppuration develops. The bacilli are 

 found in the viscera and blood. 



If a small quantity is injected, a local suppuration occurs, and 

 if the animal does not die, it then can withstand large quanti- 

 ties. It is immune. 



The Pigment. Pyocyanin. When the pus, bandages, and 



