112 



PATHOGENIC BACTERIA. 



through. To be certain of the efficacy of such a filter 

 the fluid first passed through must be tested by cultiva- 

 tion methods. The complicated Pasteur-Chamberland 

 and the simple Kitasato and Reichel filters are shown in 

 Figures 14, 15, and 16. 



After having been used a porcelain filter must be dis- 

 infected, scrubbed, dried thoroughly, and then heated in 

 a Bunsen burner or blowpipe flame until all the organic 

 matter is consumed. In this firing process the filter first 

 turns black as the organic matter chars, then becomes 

 white as it is consumed. The greatest care must be 

 exercised in cleansing, and especially must care be taken 

 that the porcelain is dry before entering the fire, as it 

 will certainly crack if moist. 



Before using a new filter it should be sterilized by dry 

 heat, then connected with receivers and tubes, also care- 

 fully sterilized. It should not be forgotten that the fil- 

 tered material is still a good culture-medium and must be 

 handled with the greatest care. 



While the filtration of water, peptone solution, and 

 bouillon is comparatively easy, gelatin and blood-serum 

 pass through with great difficulty, and speedily gum the 

 filter, so that it is useless until fired. 



A convenient apparatus used by the author for the rapid 

 filtration of large quantities is shown in the accompany- 

 ing illustration (Fig. 17). 



FIG. 17. Apparatus for the rapid filtration of toxins, etc. 



The Disinfection of Instruments, Ligatures, Sutures, 

 the Hands, etc. There are certain objects used by the 



