308 TEXT-BOOK OF BACTERIOLOGY. 



tog-ether with their capsule, in the blood and in all the organs. The 

 bacteria lie only in the interior of the blood-vessels, the whole affection 

 being thus characterized as genuine septicaemia. Morbid changes, 

 such as small round-cell infiltration, incipient necrosis, etc., are no- 

 where to be found. 



The lungs, in particular, show no visible consequences of infec- 

 tion, and they can surely not be considered as a privileged spot 

 for the settlement of the micro-organism. 



But when they are introduced directly, by injecting the infec- 

 tious matter through the thoracic wall, the pleura will, as a rule, 

 be violently inflamed. The lungs, too, are often affected and exhibit 

 more or less considerable consolidations. 



The injection of ever so small a quantity of the blood of an animal 

 having thus perished into another of the same species will surely 

 cause it to succumo to the infection. The bacillus, therefore, belongs 

 to the most virulent or infectious micro-organisms known. 



A. FraenkePs observations (as herewith briefly reported) have 

 been confirmed and amplified by a great number of different inves- 

 tigators. Suffice it to mention Monti's discovery that a genuine 

 pneumonia with all its characteristic symptoms can be produced in 

 rabbits by injecting 1 bacteria into the trachea, the shortest way to- 

 the lungs. 



The results of experiments on animals do not, however, always 

 harmonize, the efficacy of the material frequently showing great vari- 

 ations. Fraenkel himself and, after him, Weichselbaum have pointed 

 to the fact that the bacteria, taken directly from the lung tissue, 

 possess a priori a varying degree of virulence and that they, above 

 all when cultivated, rapidly fall a prey to attenuation, both natural 

 and artificial. 



Although we may perform transmission from generation to gen- 

 eration frequently and carefully, in order to prevent the premature 

 death of the micro-organisms on one medium, their efficiency will be- 

 come extinct after a certain period, while the culture, as such, is. 

 still capable of propagation. There is but one means of maintain- 

 ing their activity, and that is by a prompt renewal of the bacteria in 

 the animal body. Infection of a susceptible animal (rabbit) is best 

 made every tenth day; new cultures should then be produced from 

 its blood, and this procedure should be repeated after the period 

 stated has elapsed. 



Attenuation may likewise be brought about by the aid of high 

 temperature. By placing Fraenkel's diplococci into bouillon and 

 keeping this at 42 C. for twenty-four hours, the micro-organisms 

 will have become completely harmless. The same is the case with 



