164 TECHNOLOGY OF BACTERIA. 



body of the animal or by floating atmospheric 

 germs. It is difficult to accomplish this, however, 

 and in practice it will be found that inilk, although 

 a suitable culture-fluid for various organisms, is not 

 commonly available, owing to the difficulty of ob- 

 taining it from its source free from contamination, 

 and to the fact that it is a difficult fluid to 

 sterilize. 



Urine. Pasteur, Lister, the present writer, and 

 several other experimenters have succeeded in 

 obtaining urine, directly from the bladder, free 

 from bacterial contamination, and which, conse- 

 quently, did not undergo any change from being 

 kept, although exposed freely to the air filtered 

 and to a temperature suitable for inducing the 

 different forms of fermentation which this fluid 

 undergoes when no precautions are taken to ex- 

 clude the micro-organisms to which these changes 

 are due. 



In man, and doubtless in the lower animals also, 

 the orifice of the urethral canal is constantly in- 

 fested with bacteria of different species, whereas 

 the deeper portion of the canal and the bladder 

 are quite free from them. This is proved by 

 microscopical examination, and by the fact that 

 urine free from bacteria may be obtained by 

 taking the precaution to destroy those located in 

 the vicinity of the meatus urinarius by means of 

 a suitable disinfectant. 



The writer has on several occasions repeated 



