TEXT-BOOK OF BACTERIOLOGY. 309 



a temperature of 41° C. in^ five days. Attenuation succeeds only 

 partially when the tubes are removed from the incubator before 

 the proper time has elapsed. By inoculating a number of rabbits 

 with such attenuated material, it will be found that many of them 

 fall quite sick, but that few perish and these only after several days. 



Even after subcutaneous application, the lungs are visibly 

 changed and an inflammation of the pleura ensues, with or without 

 consolidation (as previously observed after direct injection into the 

 lungs). 



Is Fraenkel's bacillus really the genuine exciter of pneumonia? 

 Considering that this " pneumococcus," owing to its peculiar prop- 

 erties, its growth at higher temperatures, its rapid decay in arti- 

 ficial cultures, and speedy loss of virulence outside of the body, 

 appears necessarily as a strictly parasitic micro-organism, we may 

 well assume that it is destined to play a pathogenic part. The 

 transmissions also point to a special significance, especially if we 

 bear in mind that pneumonia, under natural conditions, passes to 

 animals rather infrequently and, consequently, affords to experi- 

 ments but little chance of success. 



But all these considerations are not of sufficient weight to com- 

 pel us to believe that we are dealing with the original micro- 

 organism of pneumonia, and we must again recur to the question 

 whether this bacterium is regularly and only found in inflamma- 

 tion of the lungs. It may be stated (especially after Weichsel- 

 baum's extensive investigations) that this bacterium can be proved 

 to exist in a very great majority (over 90^) of all cases. The cir- 

 cumstance of its being missed here and there is not difficult to 

 account for. Fraenkel's diplococcus cannot be surely recognized 

 as such by microscopic examination alone. It presents certain dif- 

 ficulties to cultivation (which alone can afford a reliable conclusion) 

 which are not always sufficiently heeded by all observers. Its ex- 

 clusive growth at high temperatures and its considerable sensitive- 

 ness require careful manipulation in cultivation, above all the in- 

 dispensable preparation of agar-plates. This requirement is still 

 frequently overlooked. 



Weichselbaum and Monti have, moreover, emphatically pointed 

 out another circumstance : the diplococci are found in the diseased 

 lung- tissue in much greater quantities, the fresher and younger the 

 tissue is, while in the further course of the affection they gradually' 

 diminish and may ultimately disappear altogether. The exact 

 time of observation is, therefore, of the greatest importance and 

 many failures may be attributed to this circumstance. 



All this is decidedly in favor of the specific character of the 



