488 BACTERIOLOGICAL ANALYSES 



more than o. i c.c. of the mixture within the bore when 

 the point of the pipette is clear of the fluid in the tube. 

 Touch the point of the pipette on the inner wall of the 

 tube, and allow any excess of fluid to escape, only 

 retaining o.i c.c. in the pipette. 



14. At the same time, with the left hand remove Bile 

 Salt Tube No. i from the upper tier of the rack, take 

 out the cotton-wool plug with the hand already holding 

 the pipette (the relative positions of pipette, plug and 

 culture tubes being practically the same as those of 

 platinum loop, plug and culture tube shown in Fig. 68, 

 page 74). 



15. Insert the point of the pipette into the subculture 

 tube, and blow out the mixture into the medium re- 

 plug the tube and drop it into the wire basket. Re- 

 place the washer-pipette in tube A. 



As soon as the point of the pipette has entered the 

 mouth of tube A it may be released, since it has already 

 been so adjusted that it just clears the bottom of the 

 test-tube, and the elastic washer will prevent any 

 damage to the tube. 



Steps 13, 14 and 15 occupy on an average 10 seconds. 



1 6. Repeat steps 13, 14 and 15 with each of the other 

 tubes B, C, D and E. 



17. Repeat these various steps 1316 when the bell 

 rings at 5, 25 and 30 minutes. 



18. Place all the inoculated tubes in the incubator 

 at 37 C. 



19. Examine the tubes at intervals of 24 hours, and 

 record the results in tabular form as shown in Table 

 page 491 (the figures in the squares indicate the number 

 of hours at which the changes in the medium due to the 

 growth of B. coli first appeared). 



20. If a consideration of the tabulated results indi- 

 cates strengths of Germicide-x lethal at 2j and 30 

 minutes the final test can be arranged, but if this 

 result has not been attained, sufficient evidence will 



