CHAPTEK 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. 

 It is convenient here to describe this method. In ordinary work 

 fine calibrated pipettes 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 name 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 where its 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. Thus, when pressure on the 



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