542 



PATHOGENIC MICROORGANISMS 



pertussis, while differing from the others in some of their characteristics, 

 could not properly be maintained as distinct species. 



Koch-Weeks Bacillus. — Koch,' in 1883, Weeks '' and Kartulis, in 

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

 a form of acute conjunctival inflammation, 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 incubator 

 temperature, but, unlike influenza bacilli, can be cultivated upon media 

 of serum or ascitic fluid, without hemoglobin. In fact, growth upon 

 serum-agar is more active than upon hemoglobin media.' 



Bacillus of Pleueo-Pneumonia of Rabbits. — 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 mukisbpticus 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.) 



' 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. 

 2 Kamen, Cent. f. Bakt., xxv, 1899; Weichselbaum and Muller, Arch. f. Ophthalm., 

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



