CHAPTER IV. 



METHODS OF EXAMINING THE PROPERTIES OF 

 SERUM PREPARATION OF VACCINES- 

 GENERAL BACTERIOLOGICAL DIAGNOSIS IN- 

 OCULATION OF ANIMALS. 



THE TESTING OF AGGLUTINATIVE AND SEDIMENTING 

 PROPERTIES OF SERUM. 



Wright's Method of measuring Small Amounts of Fluids. 

 In ordinary work fine calibrated pipettes (p. 73) may be used 

 for measuring small quantities of fluids, but such pipettes are 

 not always available, and by Wright's technique if a Gower's 5 

 c.mm. haemocytometer pipette be at hand any measurements may 

 be undertaken in fact, once the pipette now to be described 

 (see Fig. 43) is made we are independent of other means of 

 measurement. A piece of quill tubing is drawn out to capillary 

 dimensions, and the extreme tip of it is heated in a peep flame 

 and then drawn out till it is of the thickness of a hair, though 

 still possessing a bore. If the point be broken off this hair, and 

 mercury be run into the tube, the metal will be caught where 

 the tube narrows and will pass no further in fact, though air 

 will pass, mercury will not. Into the wide end of this tube 

 5 c.mm. of mercury, measured from a Gower's pipette, is run down 

 till it will go no further. A mark is made on the tube at the 

 proximal end of the mercury, which is now allowed to run out, 

 and the tube is carefully cut through at the mark. A piece of 

 ordinary quill tubing is drawn out and broken off just below the 

 point where narrowing has begun, the hair end of the capillary 

 tube is slipped through the broken-off end, and the tube is fixed 

 in position with wax as shown in the figure. A rubber nipple 

 placed on the end of the pipette completes the apparatus. If by 

 pressing the nipple the air be expelled from the pipette, and the 

 end dipped under mercury, exactly 5 c.mm. will be taken up 



