﻿314 The Philippine Journal of Science wu 



as to prevent the use of the immersion lens. Thickness 2, as 

 quoted in American catalogues, suits the purpose well. 



The preparation of the cover glass is a matter of great im- 

 portance to the success of the technique. One should clean the 

 cover carefully and then apply just enough vaseline or fat to 

 prevent the small hanging drops from running together, A 

 good method is to smear vaseline over a number of well-cleaned 

 covers and to place them in some convenient receptacle free 

 from dust. When the covers are to be used, they are freed from 

 the excess of vaseline by means of soap and water, cleaned 

 carefully with a dry cloth, then heated enough to soften the 

 vaseline, and rubbed again while still warm. They may then 

 be slightly moistened by the breath and rubbed again with a 

 fresh clean cloth. The aim is to remove as much vaseline as 

 possible without the use of excessive heat or any fat-dissolving 

 reagents other than soap. If an excess of vaseline is left on 

 the cover, small particles will appear in the droplets and may 

 be mistaken for bacteria. If all is removed, the droplets will 

 run together. Fine droplets placed very closely together will 

 remain separate for months on a properly prepared cover. For 

 the beginner, especially, success or failure may depend on the 

 condition of the cover glass. Cover glasses may be prepared 

 and kept in stock for use, but it is well to rub them afresh with 

 a clean, dry cloth just before sterilizing. 



As to the glass tubing, the size recommended above is the 

 best, but considerable latitude is allowable. Soft glass is, on the 

 whole, preferable, as it is more easily worked. The fine tip 

 at the end of the capillary is more easily made with hard glass, 

 but the preliminary drawing out of the capillary often requires 

 a blast flame, which is not always convenient to the working 

 table. 



To make a serviceable microburner, one has only to bend a 

 glass tube to the form shown in fig. 5, b, to heat one end, and 

 flatten it so as to form a narrow aperture. In the form shown 

 in the illustration, a clamp is fastened to the back of a wooden 

 block for convenience in adjusting the flow of gas. This block 

 may be dispensed with and the tube kept upright by the clamp 

 alone. The tip of the burner should be at a height of about 

 6 centimeters above the surface of the table. 



TECHNIQUE OP ISOLATION 



It is recommended that the beginner in this technique follow 

 strictly the directions given below and in the order given : 

 1. Clamp the pipette holder firmly to the left side of the 



