34 CLINICAL BACTERIOLOGY AND H/EMATOLOGY 



kept point upward they will remain sterile indefinitely. Of 

 course, the exterior of the glass will become contaminated, 

 and it should be passed through the flame before use. 



The ends of the tube being sealed up while the bulb contains 

 heated air, it follows that the bulb will contain a partial 

 vacuum on cooling. This fact is made use of in the collection 

 of specimens. Suppose, for instance, we wish to take some 

 blood from a heart at a post-mortem examination for investi- 

 gation at a distance. A point on the surface of the heart is 

 first seared with a hot iron to destroy any germs which might 

 be present, and the end of the pipette (still sealed) is thrust 

 through into one of the cavities. It is then broken off by 

 dexterous pressure against the heart wall, and the pipette 

 will fill slowly with the blood. Another method is to break off 

 the tip of the pipette and to warm the bulb before making the 



D 



c ^ 



FIG. 10. PIPETTES. 



puncture. The fluid will rise as the bulb cools; or both ends 

 may be broken up and the fluid drawn into the bulb by gentle 

 suction. 



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 is much used for the col- 

 lection of pus, etc., for bacteriological examination, is drawn 

 out to a point at one end only, the other being left wide and 

 separated from the bulb by a constriction (Fig. 10, 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. They are fitted with an indiarubber teat for use. 



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



