ACTINOMYCETES. 387 



appears as long, branching threads, many of which are 

 composed of short quadratic segments. Spores are not 

 formed. Motility is doubtful ; it has been observed by 

 Eppinger, while Lehman and Neumann failed to detect 

 it. It stains both by the ordinary dyes and by the 

 method of Gram. It grows scarcely, if at all, under 

 anaerobic conditions. It grows at room-temperature, 

 but much better at the temperature of the body. The 

 best growth is observed on nutrient agar-agar containing 

 2 per cent, of glucose. The colonies on the surface of 

 glucose agar-agar appear as yellowish-white, round, 

 finely granular, dull patches that are 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 

 liquefaction, 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 

 pathogenic action. When injected into either the circu- 

 lation, the peritoneal cavity, or beneath the skin, there 

 develop in from one to four weeks a condition closely 

 simulating tuberculosis (" pseudotuberculosis clado- 

 thrica"). The organism quickly loses its pathogenic 

 properties under artificial cultivation. 



