440 



PATHOGENIC MICROORGANISMS 



Communications upon lance-shaped cocci found in saliva, and 

 capable of producing septicemia in rabbits, were published almost 

 simultaneously by Sternberg ll and by Pasteur 12 in 1880. These 

 workers, beyond reasonable doubt, were dealing with the true pneu- 

 mococcus, but did not in any way associate the microorganisms they 

 described with lobar pneumonia. The solution of this problem was 

 reserved for the labors of A. Frankel 13 and Weichselbaum 14 who 

 published their results, independently of each other, in 1886, demon- 

 strating beyond question that the pneumococcm is the etiological 

 factor in a large majority of cases of lobar pneumonia. 



Recent studies by Neufeld and Haendel, and in this country by 

 Cole and his coworkers at the Rockefeller Hospital, have shown that 

 in the pneumococci we are dealing not with a single organism, but 

 with a group. In this grouping three specific types have been 

 described, named respectively, types I, II, and III, and a heterogene- 

 ous collection of organisms classified for convenience together as 

 type IV. In a subsequent section, under the main heading of 

 "Immunity and Specific Therapy," this phase of the pneumococcus 



problem is discussed at greater 

 length. 



Morphology and Staining. 

 The morphology of the pneumo- 

 coccus is, in general, one of the 

 most valuable guides to its iden- 

 tification. 



When typical, the pneumo- 

 coccus is a rather large, lancet- 

 shaped coccus, occurring in pairs, 

 and surrounded by a definite 

 and often wide capsule, which 

 usually includes the two ap- 

 proximated cocci without a defi- 

 nite indentation opposite their 

 lines of division. The pneumo- 

 cocci may, however, occur singly 

 or in short chains, and even fairly long chains are not infrequently 



FIG. 48. PNEUMOCOCCI, GROWN ON 

 LOEFFLER'S SERUM. (Capsule stain 

 by gentian-violet-potassium-carbonate 

 method.) 



11 Sternberg, Nat. Board of Health Bull., 1881. 

 ^-Pasteur, Bull, de Tacad. de med., 1881. 



13 A. FrdnTcel, Zeit. f. klin. Med., x, 1886. 



14 Wcichselbaum, Med. Jahrbueher, Wien, 1886. 



