VACCINE-THERAPY 49 



Throttled Capillary Pipettes. 



These, by reason of their mechanism, regulate the air 

 transmitted by the rubber teat, and thereby control the 

 movements of the fluid in the narrow stem. 



Two such kinds of pipettes are in common use — i.e., 

 (a) where the throttle is in the distal end of the capillary 

 stem ; (b) where a smaller pipette is inserted in the proximal 

 end of the ordinary pipette. 



(a) Take an ordinary pipette made in the manner already 

 described, and hold the end in the flame of an ordinary 

 wax vesta for a second or so, and then draw it out with a 

 sudden jerk, cut off the end with a glass knife, leaving a 

 very fine point. 



A (T 



Fig. 22. — Throttled Capillary Pipettes. 



(6) Take an ordinary pipette, and insert a short pipette of 

 smaller calibre in the proximal end of it. 



The smaller pipette is throttled in the manner as above 

 described. A coating of sealing-wax is now placed round 

 its shoulder, the proximal end of the large pipette gently 

 heated, and the small pipette inserted, the wax making a 

 tight-fitting joint. 



Method of sealing up a Test-Tube. 



When it is desired to seal a test-tube — as, for example, 

 after making a bacterial emulsion, and we wish to break 

 down the bacterial bundles, chains, etc., by shaking — it is 

 imperative that the open end should be closed. — To do this 



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