KOCH-WEEKS BACILLUS 327 



twenty-four hours old make a suspension of the bacilli in normal salt 

 solution, controlling the number of bacilli by examining a hanging-drop 

 preparation. The influenza bacilli seem to agglutinate rather slowly; 

 so it usually takes four to five hours to get a good reaction. 



Serum Therapeutics. No protective serum has been produced which 

 has any value in treatment. 



The Koch-Weeks Bacillus of Conjunctivitis. 



This bacillus was first observed by R. Koch in 1883 while making 

 certain investigations into inflammation of the eye occurring during 

 an epidemic of cholera in Alexandria. It was later, in 1887, more 

 specifically described by Weeks in New York. Weeks obtained it in 

 pure culture in 1890. 



The infective disease which is caused by this bacillus seems to be 

 very widely distributed, no land or clime probably being exempt from 

 it. In this country it occurs epidemically and with increasing fre- 

 quency during the Spring and Fall months. Weeks has found the 

 bacillus in over 1000 cases in New York City. 



Morphology. The bacilli from the purulent secretions are small and 

 slender, being not unlike the influenza bacilli but somewhat longer. 

 They vary in length from 0.5 to I/JL or even 2/t occasionally; the 

 longer forms are apparently unions of thread-like filaments. The 

 shorter bacilli not infrequently have the appearance of diplococci. 

 Sometimes they exhibit slight polar staining. Their width is very 

 constant. The ends are rounded. They are rapidly decolorized by 

 Gram. 



Staining. They are best stained by very dilute solutions of carbol- 

 fuchsin or LoefHer's methylene blue, but do not stain readily. 



In smear preparations the Koch- Weeks bacilli are, as a rule, seen 

 alone or associated with isolated cocci and bacilli, especially xerosis 

 bacilli. They are not infrequently observed within the cells, and are 

 very rarely associated with gonococci and pneumococci, such mixed 

 infections being extremely uncommon. 



Biological Characters. The Koch- Weeks bacillus grows only at incu- 

 bator temperature. Of the ordinary culture media none but moist 

 and slightly alkaline peptone agar can be employed. Special media 

 are required generally for its cultivation. The best results have been 

 obtained with serum agar or a mixture of glycerin agar and ascitic 

 fluid, 2 to 1. Pure cultures are rarely obtained at first; they are usually 

 associated with colonies of xerosis bacilli or staphylococci. After 

 twenty-four to forty-eight hours the colonies are noticeable as moist, 

 transparent, shining drops or points. Microscopically examined under 

 low magnifying power they appear like small gas bubbles; by closer 

 examination they are seen to be round, lying loosely on the surface, 

 and are readily removed. Under higher magnification a number of 

 fine points are observable. The colonies, which resemble those of 

 influenza, have a tendency to confluesce, but are not so sharply defined 



