﻿326 2"^^ Philippine Journal of Science isu 



cannot be governed by the left hand in the position described 

 above. Its scope is also limited to the simpler applications of 

 the pipette method. 



CULTIVATION OP THE ISOLATED ORGANISM 



After the single organism has been isolated, it may be 

 cultivated in situ on the cover glass or removed and grown 

 elsewhere. 



I. CULTIVATION IN SITU ON THE COVER GLASS 



1. If only a few generations of growth are to be observed, 

 one may simply leave the organism in the droplet in which 

 it was isolated and place the cover glass over an ordinary 

 moist chamber. Some organisms do not grow well in so small 

 an amount of medium, while others will form a considerable 

 number of generations. Bacterium coli commune, for example, 

 will form 32 small elements in a droplet of broth about 10 

 microns in diameter. In order to prevent drying or undue 

 concentration of the medium, the droplet should be placed near 

 a larger drop of broth or of agar. It may be necessary to 

 add to the moisture on the cover by placing slightly warmed 

 water in the bottom of the isolating chamber just before trans- 

 ferring the cover, but it is obviously unsafe to add too much 

 condensed moisture in this way, because the drops may run 

 together. 



2. With a fresh, sterile pipette (it is not necessary to make 

 a fine-pointed pipette), liquid may be taken from a test tube 

 or from a sterile hanging drop on the cover and added to 

 the droplet containing the organism. This may be done under 

 the low power. To avoid any possibility of taking up the 

 organism with the second pipette, one may discharge the large 

 drop near the small one and lower the pipette before the broth 

 has spread to the droplet. Liquified gelatin, liquified agar, or 

 any fluid or semifluid medium may be added. 



3. A very convenient method, especially when a considerable 

 number of isolations are to be made from the same source, 

 is to place on the cover glass previous to isolation a series 

 of drops of broth, melted agar, gelatin, or any other solid or 

 fluid medium. The diameter of these drops will depend on the 

 available space and the nature of the experiment — 0.5 milli- 

 meter is, perhaps, the minimum and 2 or 3 millimeters a good 

 average. These drops may be placed in a series of rows ar- 

 ranged with reference to lines on the cover, or any arrange- 

 ment may be followed, so that any drop can be easily found 



