BACTERIOLOGY. 



of the cultivations are further reduced by avoiding 

 draughts at the time of inoculation, and it is best 

 that these manipulations should be carried on in a 

 quiet room in which the tables and floor are wiped 

 "with damp cloths, rather than in a laboratory in 

 which the air becomes charged with germs through 



constant sweeping and dust- 

 ing, and the entrance and 

 exit of classes of students. 

 In conducting any investi- 

 gation a dozen or more 

 tubes should be inoculated, 

 and if by chance an ad- 

 ventitious germ, in spite of 

 these precautions, gain an 

 entrance, the contaminated 

 tube can be rejected and 

 the experiments continued 

 with the remaining pure 

 cultivations. 



Where, however, one tube is inoculated trom 

 another containing a liquid medium, as in the process 

 of preparing plate-cultures, or where a culture is 

 made from a tube in which the growth has liquefied 

 the gelatine, it is obvious that the tubes cannot be 

 inverted, and they must then be held and inoculated 

 as in Fig. 28. To inoculate those tubes of nutrient 

 agar-agar which have been gelatinised obliquely, the 

 sterilised needle with the material to be cultivated 

 is streaked over the surface from below upwards. 



FIG, 27. 



METHOD OF INOCULATING 

 A TEST-TUBE CONTAINING 

 STERILE NUTRIENT JELLY. 



