﻿328 The Philippine Journal of Science wi* 



add to the moisture. After the cover is well sealed on, it is best 

 to put the culture into a Petri dish or box, because a sudden 

 change to a higher temperature may cause too much moisture 

 to leave the cover and condense on the slide. These and similar 

 precautions will occur to any one familiar with cultivation of 

 organisms in the hanging drop ; but special precautions must be 

 taken where the drops are relatively small. 



The growth of the single organism at the edge or center of 

 the hanging drop, whether in a liquid or a solid medium, gives 

 one an excellent opportunity of observing the development of 

 young colonies. For instance, a single tubercle bacillus of some 

 strains will give a very different type of growth in the bottom 

 of a drop of broth than when left at the margin. If one 

 desires to transfer the colony grown on the cover to a test tube, 

 the cover is placed on the isolating chamber again and the 

 colony transferred by means of the pipette under the low power 

 or with a bent platinum wire without the use of the microscope. 



CXn-TIVATION IN A MEDIUM APART FROM THE COVER GLASS 



1. The organism may be taken up with a fresh sterile 

 pipette already supplied with broth and discharged into a test 

 tube containing a liquid medium, or it may be placed on the 

 surface of a solid medium in a test tube or into the water of 

 condensation. If it is desired to get an abundant growth on 

 solid media as soon as possible, one may wash the surface with 

 the water of condensation some hours after the organism has 

 been transferred to it. The removal of the organism from the 

 cover may be facilitated by adding a little sterile broth from the 

 second pipette to the droplet just before taking up the organism. 

 It is easy, of course, to transfer to a solid medium in a liquid 

 state in order to obtain anaerobic conditions. 



2. Where temporary growth is to be observed, one may take 

 up the organism in a fresh pipette and leave the pipette in 

 the holder. After any desired interval of time, the isolated or- 

 ganism with its offspring may be discharged on the cover and, 

 after inspection, drawn into the pipette again. This method is 

 sometimes convenient for organisms which do not grow well 

 in a hanging drop. 



3. If it is desired to observe growth on the cover glass and 

 the cover on which the organism is isolated is for any reason 

 unsuitable, the organism may be taken into a pipette, the pipette 

 lowered, and a new sterile cover, supplied with broth or agar 

 droplets, substituted for the old one. One has only to raise the 

 pipette and discharge the organism into any desired place on the 

 new cover. 



