16 BIOLOGY OF PNEUMOCOCCUS 



He grew the cocci on liquid and solid media, studied the most 

 favorable reaction for growth, and found that while the organ- 

 isms retained their virulence on coagulated blood serum or meat- 

 infusion agar, they lost it rapidly in broth because of its changed 

 reaction during incubation. Young cultures were highly patho- 

 genic for mice and rabbits, less so for guinea pigs, and avirulent 

 for dogs, pigeons, and chickens. 



Fraenkel was able to isolate the diplococcus from all cases of 

 true fibrinous pneumonia, grew it in pure culture, produced a fatal 

 septicemia in susceptible animals, again recovered from them the 

 organism in a pure state, and then further transmitted the infec- 

 tion to other test animals. His results therefore met all the require- 

 ments of Koch's law, and it would seem that Fraenkel was the first 

 to establish the fact beyond a reasonable doubt that Pneumococcus 

 was the causative agent in lobar pneumonia. 



Fraenkel 468 made another important and original contribution 

 when he reported that rabbits, recovering from a subcutaneous in- 

 fection of the ear, resisted a subsequent inoculation with the same 

 coccus. Although Foa and Bordoni-Uffreduzzi had independently 

 discovered the same phenomenon (1884), this is probably the first 

 controlled observation that pneumococcal infection may induce 

 immunity. 



Fraenkel also found Pneumococcus in the exudates in the pia 

 mater from a case of meningitis accompanying pneumonia, but was 

 unable to decide which lesion was primary. Senger (1886) 1255 had 

 seen these diplococci in amazing numbers in fluid from the sub- 

 arachnoid and ventricular spaces in similar cases and, in addition, 

 in the lesions of endocarditis, pericarditis, pleuritis, and nephritis 

 of pneumonia patients. He was, of course, correct in supposing 

 that these and other metastases might be expected to arise from a 

 pulmonary lesion. Netter, 962 " 3 ' 965 and also Lancereaux and Be- 

 sancon, 778 reported the same findings in two corresponding cases of 

 meningitis, pericarditis, and endocarditis. Lebashoff, 795 in Russia, 

 at this time announced similar observations on the occurrence of 



