ESTIMATION OF THE OP SONIC POWER OF THE BLOOD 203 



knitting-needle or a little less, and a foot or more long). This 

 will give two pipettes, and to separate them melt the central 

 portion in a small flame, such as that of a wax vesta, and 

 when the g'lass is softened pull them quickly apart. The 

 whole pipette should be like this 



- ^ 



FIG. 35- 



The lower figure represents the point, which must have as 

 nearly as possible the shape represented in the figure. The 

 ease and accuracy of the process depends in great measure on 

 this being' the case. 



The Process. i. Prepare a pipette by placing an india- 

 rubber nipple on the thick end. Then with a grease pencil or 

 with pen and ink make a transverse line about i inch from the 

 pointed end. The volume of fluid contained in the tube 

 between the point and this mark is spoken of as the unit. 



2. Having the patient's serum, the emulsion of leucocytes, 

 and the emulsion of bacteria, ready in front of you, take the 

 pipette between the index-finger and thumb of the right hand, 

 and compress the nipple. Immerse the point beneath the sur- 

 face of the emulsion of bacilli and relax the pressure on the 

 nipple until the emulsion has risen exactly to the mark, so 

 that you have drawn up one unit; then remove the point from 

 the fluid and relax the pressure again, so that a small column 

 of air will be sucked up. This will be quite easy if the point 

 is a good one; otherwise it will be difficult or impossible, as 

 the column of fluid will either refuse to stir or will oscillate 

 violently. 



Next immerse the point in the emulsion of leucocytes and 

 draw up one unit. This will be separated from the emulsion 

 of bacteria by the short column of air. Remove the point 

 from the emulsion and draw up a second column of air; 

 reinsert it and draw up a second unit of leucocytes, and then 

 a third column of air. 



Lastly, draw up one unit of the serum. You will then have 

 in your pipette (counting from the nipple towards the point) 



