Cultivation 407 



Morphology. The organism is very tiny and is said to bear 

 some resemblance to the bacillus of mouse-septicemia. It measures 

 i to 2 X 0.25 JJL (Weeks). The length is more constant in individuals 

 found in the pus than those taken from cultures. In cultures the 

 organisms are longer and more slender. Involution forms of con- 

 siderable length and of irregular shape also occur. No spores are 

 observed. The organism has no flagella and is not motile. 



Staining. Weeks found that the organism stained well with 

 watery solutions of methylene blue, basic fuchsin, or gentian 

 violet. The color is fainter than that of the nuclei of the associated 

 pus-corpuscles, and is much less intense in old than in fresh cultures. 

 It is readily given up when treated with alcohol or acids. Morax 

 found that the bacilli did not retain the color in Gram's method. 



Fig. 148. The Koch- Weeks bacillus in conjunctival secretion. Magnified 1000 

 diameters (Rymowitsch and Matschinsky). 



Cultivation. The organism refuses to grow upon any of the 

 ordinary culture-media. Weeks found, however, that if the per- 

 centage of agar-agar used was reduced to 0.5 per cent., growths 

 could be secured by incubation at 37C., and successful transplanta- 

 tions carried on to the sixteenth generation. Abundant moisture 

 was essential. The method of isolation adopted by Weeks was as 

 follows : 



"The conjunctival sacs were thoroughly washed with clean water, removing 

 the secretion present by means of absorbent cotton. The patient was then 

 directed to keep the eyes closed. After five or ten minutes had elapsed, the eyes 

 were opened, and the secretion that had formed, lying at the bottom of the cul- 

 de-sac, was removed by means of a sterilized platinum rod and transferred to the 

 surface of the agar. The mass of tenacious secretion was drawn over the surface 

 of the agar and left there, the platinum being thrust into the agar two or three 

 times before removal." 



At the end of forty-eight hours a slight haziness appears along 

 the path of the wire, and on the surface of the agar a very small 



