110 



BACTERIOLOGICAL ANALYSIS 



Aspirator 



FIG. 6. 



a, Bent glass tube 3 to 5 mm. 

 in diameter: &, india-rubber 



stopper ;c , filtering flask ; d, 

 broth - 



This is a rough method and of comparatively little 

 use. 



II. ASPIRATION THROUGH BROTH. 



Put up an apparatus as shown in the diagram (Fig. 6). 



(1) Into the flask (c) pour 50 

 cc. of sterile beef broth ; close it 

 with an india-rubber stopper (6), 

 and pass the bent tube (a) through 

 the perforated stopper into the 

 broth. 



(2) Now plug the free end of 

 the bent tube and of e with 

 cotton -wool, and sterilise the 

 whole apparatus in the autoclave. 



(3) When the flask and broth have cooled down, remove 

 the cotton-wool plug at a and slowly aspirate air through 

 the flask by means of the air-pump. 



Continue the aspiration for half an hour to one hour. 



(4) Now again plug a with sterile cotton-wool. 



(5) Liquefy several tubes of gelatine, and to each add 

 05 to ! cc. of the broth through which the air has been 

 aspirated, and prepare plates in the ordinary manner. 



(6) Keep the plates in a cool incubator ; examine them 

 and count the colonies from day to day. 



Colonies should be examined, both microscopically 

 and by means of subcultures, as they appear. 



III. FILTRATION THROUGH SUGAR. 



(1) Powder a little loaf sugar as finely as possible. 



