542 



PATHOGENIC MICROORGANISMS 



pertussis, while differing from the others in some of their character- 

 istics, could not properly be maintained as distinct species. 



KOCH- WEEKS BACILLUS. Koch; 1 in 1883, Weeks 2 and Kartulis, in 

 1887, described a small Gram-negative bacillus found in connection 

 with a form of acute conjunctivitis which occurs epidemically. The 

 bacillus is morphologically similar to B. influenzae, but is generally 

 longer than this and more slender. The bacilli grow only at incuba- 

 tor temperature. Recent studies by Anna Williams at the New York 

 Department of Health seem to indicate that the Koch-Weeks bacillus 

 may be merely a variety of the true influenza bacillus. 



BACILLUS OF PLEUKO-PNEUMONIA OF BABBITS. This is a small 



FIG. 115. KOCH- WEEKS BACILLUS. 



Gram-negative bacillus, described by Beck, not unlike that of influenza. 

 These microorganisms are slightly larger than the Pfeiffer bacilli and 

 grow upon ordinary media even without animal sera or hemoglobin. 



BACILLUS MURISEPTICUS AND BACILLUS RHUSIOPATHI^E. While mor- 

 phologically similar to the microorganisms of this group, these bacilli 

 are culturally easily separated because of their luxuriant growth on 

 simple media. (The last two microorganisms are more closely related 

 to the groups of the bacilli of hemorrhagic septicemia. See page 551.) 



1 Koch, Arb. a. d. kais. Gesundheitsamt, iii; Cent. f. Bakt., 1, 1887. 



2 Weeks, N. Y. Eye and Ear Infirmary Rep., 1895; Arch. f. Augenheilk., 1887. 



s Kamen, Cent. f. Bakt., xxv, 1899; Weichselbaum and Matter, Arch. f. Ophthalm., 

 xlvii, 1899; Knapp, Studies from Dept. of Path., Coll. of P. and S., 1903. 



