468 APPLICATION OF METHODS OF BACTERIOLOGY 



surrounded by a narrow paler zone. In the depths of the 

 medium they do not develop beyond very small points. 



On gelatin the growth is very slow; there is no lique- 

 faction, and after a time the colonies take on an orange-red 

 color. 



Bouillon is not uniformly clouded. Growth takes place 

 on the surface in the form of a whitish pellicle, in which 

 dense white masses may be seen. These latter increase in 

 size, become detached, and fall to the bottom of the vessel, 

 to collect as mycelium-like sediment. 



On potato, growth begins as a coarsely granulated white 

 layer, which becomes gradually red in color. It is ultimately 

 covered by a fine, hair-like growth. 



Both rabbits and guinea-pigs are susceptible to its patho- 

 genic action. When injected into either the circulation, the 

 peritoneal cavity, or beneath the skin, there develop in from 

 one to four weeks a condition closely simulating tubercu- 

 losis (" pseudotuberculosis cladothrica")- The organism 

 quickly loses its pathogenic properties under artificial 

 cultivation. 



Actinomyces Pseudotuberculosis. In 1897 Flexner detected 

 this organism in a consolidated and caseous lung. The con- 

 dition suggested tuberculosis. The lesion consisted mainly 

 of an inflammatory exudation that had undergone casea- 

 tion, but in addition there were present isolated nodules 

 that in size and general appearance were difficult to distin- 

 guish from miliary tubercles. Giant cells were not seen. 

 The streptothrix was abundant in the lung, appearing as 

 masses of convoluted, branching threads. The contours of 

 the rods were not quite uniform, the staining was irregular, 

 and occasionally a thread was seen that, toward its extrem- 



