412 ACTINOMYCETES. 



employed. Of these, we always use that of Ziehl- 

 Neelsen. 



Also, Gram's method is successful, but is not especially 

 recommended, since it does not possess the advantage of a 

 specific reaction. 



Relation to Oxygen. — Without oxygen, no growth. 



Requirements as to Temperature and Reaction of 

 Nutrient Media. — Growth occurs between 29° and 42°, 

 the optimum being 37°. Under all circumstances growth 

 is slow. 



Preliminary Remarks Concerning Cultures. — 

 Upon the ordinary agar and gelatin nutrient media the T. 

 B. grows scantily or not at all. For its cultivation, be- 

 sides solidified blood-serum, glycerin-agar is almost exclu- 

 sively employed (Nocard and Roux, C. B. I, 404). 



Glycerin-agar Plate. — Surface colonies like those on 

 the glycerin-agar streak. 



Glycerin-agar Streak. — At first there are minute, 

 crumbly growths, irregular in form, white to yellowish- 

 white, fairly elevated, devoid of luster or faintly glistening 

 (61, i). Later, after three to four weeks, the colonies grow 

 out and have lobulated sinuate borders. The peripheral 

 portions are still thinly transparent, and at intervals there 

 are formed elevations, like mountain ranges, running from 

 the border toward the center, which gradually converge to 

 form a mountain stem in the middle. The elevations are 

 usually yellowish to brownish in color; the depressions, 

 whitish to grayish-yellow. Still later the entire colony 

 becomes brownish (61, n). We once obtained an orange 

 discoloration. Hiippe reports that he has grown cultures 

 which presented a pronounced yellow to reddish-yellow 

 color. (See p. 430. ) Kitasato cultivated a luxuriantly 

 growing variety of Myc. tuberculosis. (Compare Myc. 

 tub. avium, p. 418.) 



Blood- serum Streak. — A slight growth in the form of 

 light-colored, dry, crumbly scales becomes visible micro- 

 scopically after about six days and macroscopically after 

 ten to fourteen days. Blood-serum is never liquefied. 

 When magnified sixty times, the colonies, especially at 

 the borders, present S-shaped flourishes consisting of 

 nothing but parallelly arranged rods (61, v). 



