BACTERIOLOGY. 201 



cultivating them at 37°C. The greater difficulty sometimes is, 

 in our opinion, to obtain a satisfactory immune serum. We gave 

 several rabbits repeated intravenous injections of large doses 

 of killed virulent cultures without obtaining more than a trace of 

 agglutination with their sera. We can strongly recommend the 

 use of the living avirulent culture for the preparation of the 

 immune serum. 



In conclusion, we can only warn against the use of cultures 

 grown at ice-box temperature as recommended by Shibayama' 

 for the agglutination tests. Although such cultures are readily 

 agglutinable, flocculation in the control tubes is apt to be very 

 confusing. If one has a satisfactory immune serum, the culture 

 grown at 32° C. or even at 37 °C. will be agglutinated promptly 

 and the control tubes will remain practically unchanged. Con- 

 trols with normal serum should always be prepared in performing 

 the test. 



INFECTIVITY OF THE EXCRETA. 



In no other disease is the infecting organism found in such 

 abundance in the sputum as it is in pneumonic plague. When the 

 disease is well developed. Bacillus pestis is present in almost 

 pure culture. In pneumonic plague as in bubonic plague, when 

 the disease becomes septicsemic, the organisms are sometimes 

 found in the urine and even sometimes in the faeces. When once 

 the sputum of pneumonic-plague cases becomes thoroughly dried 

 it is no longer infectious, but when the sputum becomes frozen 

 and pulverized, particles of it may be blown about and remain 

 infective for long periods of time or until the sputum is again 

 thawed. 



BACTERIOLOGICAL DIAGNOSIS OF PNEUMONIC PLAGUE. 



EXAMINATION OP THE SPUTUM, 



A bacteriological diagnosis from the sputum can not be made 

 at the onset of the disease, and not until after the fever has 

 developed does the sputum appear. Shortly after the appearance 

 of the sputum, the plague-organism, even if not visible from the 

 microscopical examination, may be isolated by culture. When the 

 sputum becomes bloody, the organism is usually present in large 

 numbers and in almost pure culture. Sometimes the organism 

 might be mistaken morphologically for Diplococcus pneumoniae, 

 and bipolar-staining organisms, other than plague bacilli, may 



*Centralbl. f. Bakt. etc., Orig. (1905), 1 Abt. 38, 482. 



