A STUDY OF FILTERABLE VIRUSES 313 



EXERCISE 9. A STUDY OF FILTERABLE VIRUSES 



Apparatus. Physiological salt solution; Chamberland 

 filter with water-suction or air pump and pressure gage; 

 sterile flasks; clinical thermometer; syringe; flasks of bouil- 

 lon, 50 c.c. in each; autopsy set. 



Culture. Hog cholera virus (blood of hog sick with 

 cholera) . 



Method. 1. Preparation of the Filter. If the filter has 

 been used once clean it by: 



(a) First rinsing with cold water under the tap. 



(6) Force about 1 liter of cold distilled water through 

 it. 



(c) Then a solution consisting of 1 gm. KMn(>4 and 6.5 

 gms. HC1 in 1000 gms. water. 



(d) Next, 1000 c.c. of a solution of 1% oxalic acid. 



(e) Boiling water is then forced through the filter until 

 the liquid which runs through is free from acid. 



(/) Lastly, cold distilled water must be forced through 

 the filter. 



Thus treated, any organic residue is destroyed and the 

 filter is as good as new. 



This method of purification must always be used imme- 

 diately after using a filter. Filter candles must not be left 

 twenty-four hours without cleaning. 



A new filter may be prepared for use by forcing through 

 it a large quantity of boiling distilled water and finally 

 cold distilled water. 



The amount of liquid necessary to force through the 

 filter for cleaning varies with the size of the filter. The 

 ordinary 8 inch filter should receive the full amount 

 (1000 c.c.) of each solution and distilled water for efficient 

 purification. 



Filters are best sterilized by being set up ready to use 

 and autoclaved. (See Fig. 71 for one method.) 



2. Procure some hog cholera virus and after diluting it 



