310 TEXT-BOOK OF BACTERIOLOGY. 



bacteria. There is, however, one fact which prevents our forming- 

 a conclusive opinion. 



Fraenkel's bacteria are by no means exclusively found in pneu- 

 monia; they are, on the contrary, very extensively diffused. They 

 are found in almost all cases of cerebrospinal meningitis (as proved 

 by Foa and Bordoni-Uflreduzzi) and the origin of this affection is 

 reasonably attributed to them. A. Fraenkel has found them pres- 

 ent in pleuritis, Weichselbaum in peritonitis, Banti in pericarditis,, 

 other investigators have encountered them in endocarditis and otitis 

 media and numerous other affections; they occur especially in the 

 saliva and nasal secretions of healthy persons (as established by 

 Netter) and they may be regarded almost as regular tenants of 

 these localities. 



A worse offense against Koch's law of the properties of a specific 

 micro-organism cannot be imagined. Must not our whole struc- 

 ture so artificially built up from observations and reflections col- 

 lapse in the face of this one fact ? Can we seriously believe for a 

 moment that such an ordinary, common bacterium should be cap- 

 able of producing a disease as typical and as clearly circumscribed 

 as pneumonia ?, 



Still to prove that this is not the case is not so easy as may be 

 supposed. Fraenkel's diplococcus is, indeed, not the exciter of 

 pneumonia alone, its domain is more extensive; it does not restrict 

 itself to this one function. 



Fraenkel's bacterium is the principal exciter of inflammable 

 processes of an infectious nature in the human body. Wherever 

 it reaches a serous or mucous membrane and meets with the re- 

 quirements for its settlement, it commences operations; it causes 

 meningitis on the pia mater, peritonitis on the peritoneum, and 

 otitis in the auditory passage. Whenever it gains entrance into 

 the lungs, pneumonia is developed, the peculiar properties and 

 characteristic process of which depend upon the peculiarities of the 

 organ invaded and upon the extent of the morbid process. An- 

 other bacterium may eventually play a similar role and give rise to 

 pneumonia; but, as a rule, it is certainly Fraenkel's diplococcus 

 that displays here its energy, for which reason it may properly 

 be regarded as the real micro-organism of genuine croupous lung- 

 inflammation. 



But how can this view be harmonized with the circumstance 

 that this micro-organism is also a frequent guest in the healthy 

 body, that in the majority of all persons it is domesticated in 

 the mouth, whence it might easily and at all times undertake an 

 excursion into other regions and thus soon produce meningitis. 



