STANDARDIZATION OF DISINFECTANTS 241 



phenol are tested first, as it will not be necessary to plant them 

 after 7^ min. The weaker solutions are then immediately done 

 and are planted every 2>^ min. for 15 min. 



For keeping the time a stop watch can be used, but an ordinary 

 watch will serve the same purpose by simply starting on the 2> or 

 5 min. periods. 



^When everything is in readiness the culture is added to the 

 disinfectant solutions with a sterile pipette in tenths of a cubic 

 centimeter. 



To add the culture, the seeding tube containing the disinfectant 

 is removed from the water bath with the left hand and slanted at 

 an angle of about 45, and with the right hand the end of the 

 pipette containing the culture is introduced and lightly touched 

 against the side of the tube where the liquid has run away on 

 account of slanting. At the proper time the culture is allowed to 

 run into the disinfectant solution, the pipette removed, the tube 

 straightened up, gently shaken three times, and replaced in the 

 water bath. The other tubes are done the same way in succession, 

 ancHt will be found that 15 sec. is ample time for each tube. By 

 adding the culture to the disinfectant with a pipette touched 

 against the side of the seeding tube, accurate measurements can 

 be made and each tube receive exactly the same amount of 

 "seeding," which is not the case when the culture is added by the 

 "drop. 7 ' 



If ten tubes are to be inoculated, only a few seconds will remain 

 after inoculating the last tube before a plant from the first tube 

 will have to be made. 



The mixing tubes are not removed or disturbed in making the 

 planting except to insert the loop or spoon into them, touch the 

 bottom, withdraw, and then make the plant in broth. Every 

 effort is made to insert and withdraw the loops and spoons in a 

 uniform manner. The loops and spoons are bent to an angle of 

 about 45 where they are joined on to the shank, and therefore are 

 always filled with the mixture when withdrawn from the seeding 



