496 



PATHOGENIC MICROORGANISMS 



is coughed up from the bronchi and is uncontaminated by micro- 

 organisms from the mouth. It may be washed in sterile water or 

 bouillon before transplantation, to remove the mouth flora adherent 

 to the outer surface of the little clumps of pus. The blood of pigeons 

 or that of rabbits may be substituted for human blood. 



For isolation of the organisms on plates from sputum or other 

 sources, the best medium to use is the Avery sodium oleate blood 

 medium described in the section on technique. The sodium oleate 

 in this medium inhibits a great many of the contaminating organisms 

 and seems to favor the growth of influenza bacilli. 



FIG. 50. BACILLUS INFLUENZA; Smear from sputum. (After Heim.) 



In place of this medium, blood agar plates can be used, rabbit's 

 blood being, in our opinion, somewhat more favorable than other 

 varieties of blood. It is best prepared in small lots by puncturing 

 a rabbit's heart with a sterile needle and transferring the blood 

 directly to tubes of melted agar. 



For further cultivation, the best medium is a chocolate agar 

 made as described in the section on media, in which a 5 or 10 per 

 cent rabbit's blood agar with a P H of 7.8 is heated to about 90 C. 

 (but not boiled), and plates are prepared by shaking this brownish 

 discolored medium, pouring it into plates or tubes and letting it 

 cool before all the blood has settled to the bottom. For fluid cul- 

 tivation, chocolate broth may be similarly prepared and filtered 

 through cotton or paper while hot. This makes a transparent straw- 

 colored fluid on which influenza bacilli grow with great speed and 



