Methods of Determination of Pathogenic llicrobes. 131 



the flame so as to reduce it to capillary dimensions; 

 the capillary segment which has been perfectly ster- 

 ilized by the heat is then closed at its two ends. 

 When used, it is flamed, the two ends broken off", 

 and one of them introduced into the liquid contain- 

 ing the seed, which ascends by capillarity: the tube 

 is then passed into the. culture medium and a drop 

 of the fluid expelled by blowing at the other end. 

 Such a tube can only be used once. 



3d. Pasteur's pipette. — Pasteur has designed a special 

 pipette for collecting and sowing, in a state of purity, 

 liquids containing germs. It consists of a glass tube 

 five or six centimeters in length and about one centi- 

 meter in diameter; this tube is drawn out and closed 

 at one of its extremities the other being provided 

 with a constriction, and filled with wadding; the 

 whole is sterilized at 150°. In using it, the slender 

 end is flamed, the point broken oflf, and the fluid con- 

 taining the seed, — blood, various serosities, urine, pus, 

 cultures, etc. — aspirated into the tube. The pipette is 

 then introduced into the medium to be inoculated and 

 one or two drops allowed to flow out. A liquid con- 

 taining bacteria may be preserved in this tube for 

 some time by taking the precaution to seal the capil- 

 lary extremity in the flame. The Pasteur pipette can 

 be used for sowing fluid media only; the platinum 

 wire serves equally well for both fluid and solid 

 media. 



Placing at a suitable temperature. 



Whilst most germs are able to grow at the tem- 

 perature of 15° to 20° C, many of them grow better 

 at a temperature of 30° to 40°, and a certain number 

 are able to grow at this temperature only. 



