BLOOD CAPSULES 23 



5. The jar for holding soiled pipets should contain a layer of cotton, 

 otherwise, the tip may be broken off when the pipets are dropped in. 



BLOOD CAPSULES 



Blood capsules were devised by Sir A. Wright for collecting small 

 amounts of blood for examination. The essential features of a capsule 

 are: (a) The upper straight limb, which can be drawn out to serve as a 

 needle for puncturing; (6) the recurved limb, which makes it possible 

 to fill the capsule by gravity, without risk of the inflow being arrested 

 by the blood running down and blocking the straight limb, which pro- 

 vides an outlet for the air. 



These capsules are easily made and prove quite serviceable, es- 



FIG. 5. METHOD OF MAKING A WRIGHT BLOOD CAPSULE. 



pecially for collecting small amounts of blood for making agglutination 

 tests, opsonic measurements, etc. 



1. Take a piece of soft glass tubing about 10 or 12 cm. in length, and 

 having an internal diameter of at least 5 mm. 



2. Draw one end out into a capillary stem, and break this at an ap- 

 propriate point (Fig. 5) . 



3. Then reinsert the tube into the flame, and, leaving a portion at 

 least 3 cm. in length to serve as the barrel of the capsule, draw out the 

 tube into a capillary stem about 8 cm. in length, and bend it so as to 

 form a stout recurved limb lying in the horizontal plane; now, before 

 the glass has lost its plasticity, draw the capsule gently upward so that 

 its long axis will be at an angle of about 30 horizontally. Finally, sepa- 

 rate the capsule from the main tube by filing it across the capillary por- 

 tion at the distance indicated in the accompanying illustration (Fig. 5). 



