﻿342 The Philippine Journal of Science isu 



table filament. These methods have not been tested by me, and 

 are given only as suggestions. 



DILUTIONS 



It is possible to make dilutions of a serum or other fluid under 

 the microscope with the pipette. A pipette with a tip bent some- 

 what backward is made, and a mark is made on the capillary 

 below the point of the tip. The pipette is filled to the mark with 

 serum by dipping the tip in a hanging drop, and then the mark is 

 brought into focus with the low power. The contents are ejected 

 in a hanging drop, and an equal quantity of salt solution is added. 

 These are mixed in the pipette, and one or more portions of the 

 first dilution are added to one or more of salt solution, and so on. 

 If desired, a hanging drop may be made to contain a measured 

 quantity of liquid. For measuring, a special pipette is made (fig. 

 14) . This capillary is made of hard glass, preferably, and after a 

 point is made and turned the capillary is bent into the position 

 shown and the upper side of the triangle is marked with a very 



fine capillary or pen dipped into 

 India ink or asphalt cement. 

 After the pipette is placed in the 

 holder, one can estimate the 

 Fig. 14. Special pipette for measuring small cubic contents of the different 



quantities of liquid. , « ,i .n i 



segments of the capillary by 

 measuring the length and diameter of each with the eyepiece 

 micrometer. The tip is brought into the center of the low power 

 and filled from a large hanging drop. By focusing down and 

 moving the nose piece, or the right-and-left adjustment of the 

 pipette holder, to and fro, one can bring the different marks into 

 view and discharge a hanging drop containing the quantity lying 

 between any two marks. If desired, the contents of a given 

 portion of the capillary may be more exactly measured by filling 

 it with mercury and weighing the amount of mercury ejected 

 when it is emptied. 



It is hardly necessary to state that these measuring methods 

 are applicable only when the amount of condensed moisture on 

 the cover is constant and small. However, the method has been 

 found useful in making a series of drops of approximately the 

 same size. If very small drops are needed, the eyepiece microm- 

 eter may be focused on the capillary and used in determining 

 the length of the column of liquid to be ejected. 



WARM BOX 



A series of isolations can be made with the microscope inclosed 

 in a warm box. In an apparatus used by me for determining 



