130 ESSENTIALS OP BACTERIOLOGY. 



immunity. The cultures are first heated for one half hour at 

 100 C., which destroys the germs, and then this sterilized pro- 

 duct injected. (5 c.cm. of a five days' old sterilized culture.) 



In a couple of weeks 1 to 2 c.cm. of the infected blood can be 

 injected without causing any fatal result. 



A great many more spirilla resembling the spirillum of chol- 

 era have been isolated from drinking-waters in the past few 

 years, and some bacteriologists are inclined to consider them 

 as varieties of the true cholera spirillum which require only 

 certain conditions to make them pathogenic. Among these, 

 besides those already described, are Spirillum Berolinesis, S. 

 Dunbar, S. Danubicus, S. Wernicke, S. Bonhoff, S. Weibeli, S.. 

 Schuylkiliensis, S. Milleri, S. Aquatilis. The last two are non- 

 pathogenic for experiment animals. 



Bacteria of Pneumonia. Two forms of bacteria have been 

 found in this disease, and thought at different times to be the 

 cause of the same. 



Neither one of them is constant in pneumonia ; and since 

 many other pathological processes have shown them they can 

 hardly be set down as the sole cause of pneumonia. 



Klebs in 1875 called attention to the presence of bacteria in 

 pneumonia, and in 1882 Friedlander developed a bacillus from 

 the lung tissue of a pneumonic person, which he thought was a 

 coccus, and called it pneumococcus. 



In 1886 A. Frankel and Weichselbaum proved that this 

 microbe was not constant, in fact was rare. 



A. Frankel obtained in the majority of cases of pneumonia a 

 microbe that he had described in 1884 under the name of 

 sputum-septicaemia micrococcus. 



Weichselbaum called it " Diplococcus pneumonias" and be- 

 lieved it to be the real cause of pneumonia. It has been found 

 in many other serous inflammations, and also in the mouths of 

 healthy persons. It is the generally accepted -organism of the 

 disease, and can be isolated from nearly all cases of acute 

 croupous pneumonia. It is found in about three-quarters of 

 all cases of pneumonia. 



Streptococcus pyogenes and staphylococcus pyogenes aureus have 

 been found in some cases. 



