PIPETTES 



35 



Under any circumstances both ends of the pipette must be 

 sealed up in a flame (the flame of a wax match will answer at a 

 pinch), and the tube labelled. 



Another variety of pipette which was much used for the collec- 

 tion of blood for the purpose of testing the serum reaction for 

 typhoid fever, is drawn out to a point at one end only, the other 

 being left wide and separated from the bulb by a constriction 

 (Fig. 14, b). The open end should be loosely plugged with 

 cotton-wool, and serves as a mouthpiece. The manufacture of 

 these pipettes presents a little difficulty, but a small amount of 

 practice will enable the practitioner to turn out a perfectly 

 serviceable one on occasion. 



Wright's blood capsules (Fig. 15) are the best contrivances for 

 collecting blood when the serum has to be examined, and have 

 quite replaced the pipettes described above. They can be pre- 

 pared easily after a little practice, or may be bought from 

 R. B. Turner, 11, Foster Lane, E.C., at a moderate price. 



A Wright's blood capsule consists of a piece 

 of glass tubing which is drawn out straight to a 

 narrow point at one end, whilst the other, also 

 drawn out to a point, is curved round parallel 

 with the main tube in the shape of a U (Fig. 15). 

 To use it, proceed as follows : Prick the patient's 

 ear, or, if you prefer it, the finger (after the 

 application of a wide indiarubber band), and 

 squeeze out a lai;ge drop of blood. Place the 

 tip of the curved end of the pipette in this drop, 

 holding the pipette with the straight end point- 

 ing upward (Fig. 16), and you will find that the 

 blood will run rapidly into the curved tube by 

 capillary attraction; continue to squeeze out 

 more blood and to suck it up until you have 

 collected as much as you want. It should be 

 quite easy to get the pipette half full. Then gently warm the 

 tapering portion of the straight end of the pipette in a spirit-lamp 

 or match-flame, and afterwards seal the tip (Fig. 17). As the air 

 which is now imprisoned in the upper part of the pipette contracts 

 it will suck the blood from the curved limb into the body of the 

 pipette, which can be inverted and the blood shaken into the tip, 

 but take care not to do this u;itil the glass is cold, as the serum loses 

 some of its properties when heated. If you are not going to 





Fig. 15. (About 

 f full size.) 



