384 



BACILLI IN CHRONIC INFECTIOUS DISEASES. 



serum. The growth at the end of fourteen days is more abundant than 

 upon blood serum at the end of several weeks. When numerous 

 bacilli have been distributed over the surface of the culture medium 

 a rather uniform, thick, white layer, which subsequently acquires a 

 yellowish tint, is developed ; when the bacilli 

 are few in number or are associated in scattered 

 groups separate colonies are developed, which 

 acquire considerable thickness and have more 

 or less irregular outlines ; they are white at 

 first, then yellowish- white. Frankel describes 

 the tubercle bacillus as a facultative anaerobic, 

 and it would appear that it must be able to grow 

 in situations where it can obtain very little oxy- 

 gen from its development in the interior of tu- 

 berculous nodules, lymphatic glands, etc. But 

 in stick cultures in glycerin-agar development 

 only occurs near the surface, and not at all in 

 the deeper portion of the medium. In view of 

 its abundant growth on the surface it is diffi- 

 cult to understand this failure to grow along 

 the line of puncture, if it is in truth a faculta- 

 tive anaerobic. 



In peptonized veal broth containing five per 

 cent of glycerin the bacillus develops at first in 

 the form of little flocculi, which accumulate at 

 the bottom of the flask and which by agitation 

 are easily broken up. At the end of two or 

 three weeks the bottom of the flask is covered 

 with similar flocculi, which form an abundant 

 deposit. 



Pawlowski and others report success in cul- 

 tivating the tubercle bacillus upon the surface 

 of cooked potato enclosed in a test tube after 

 the method of Bolton and Roux. The open end 

 of the tube is hermetically sealed in a flame 

 after the bacilli have been planted upon the 



obliquely-cut surface of the potato ; this prevents drying. Ac- 

 cording to Pawlowski, better results are obtained if the surface of 

 the potato is moistened with a five-per-cent solution of glycerin. The 

 growth is said to be seen at the end of about twelve days as grayish, 

 dry-looking flakes ; at the end of three or four weeks it forms a dry, 

 smooth, whitish layer, and no further development occurs. 



The range of temperature at which this bacillus will grow is 

 very restricted ; 37 C. is usually given as the most favorable point, 



FIG. 120. Culture of tu- 

 bercle bacillus upon glyce- 

 rin-agar. Photograph by 

 Roux. 



