530 



ILL USTRA TI VE EXPERIMENTS 



With a pipette drawn to a fine point put into each tuhe the number of drops 

 of 0-5 per cent, sodium chloride indicated by the figure on the tube. Rinse the 

 pipette thoroughly with distilled water. Using the same pipette, add 1 drop 

 of distilled water to tube 24, 2 drops to tube 23, and so on, till 11 drops are 

 put into tube 14. Mix. That is, there are now 25 drops of fluid in each tube, 

 giving a graduated series of percentages of NaCl. Thus : 



Add 1 drop of blood (0-1 c.c.) to each tube. Allow to stand at room 

 temperature for 1-2 hours. The test is recorded by + signs, + + + repre- 

 senting complete haemolysis, -\ — |- partial and + initial haemolysis. The 

 dilution in which there is just a slight haemolysis is noted as the point of initial 



haemolysis. Complete haemolysis is 

 indicated by the absence of intact 

 corpuscles at the bottom of the tube. 



65. Determination of the Relative 

 Viscosity of Blood (see Experi- 

 ment 31). 



Blood may be taken from the lobe 

 of the ear or from the finger. The skin 

 is thoroughly cleansed with ether and 

 pricked with a fine pointed lancet. The 

 viscosimeter (at body temperature) is 

 held vertically under the bleeding 

 spot and the receiver filled (Fig. 110). 

 Measure as in Experiment 31. 



Immediately after an observation, 

 the blood should be driven out by a 

 blast from an inflator attached by 

 rubber tubing to the short arm of 

 the capillary. 



It is advisable to make a blood 

 count at the same time. 



66. Clotting Time of Blood. 

 Thoroughly clean two watch 



glasses (1-J- in. diameter). 

 Clean the lobe of the subject's ear with ether and puncture it with a sterile 

 lancet. Allow a large drop of blootl to fall on to one of the watch glasses (as 

 the blood falls set a stop watch going). Add a small lead shot to the blood 

 and cover by inverting the second glass over the first one. Rock the glasses 

 gently and note that, with increasing viscosity of the blood, the extent of 

 movement of the shot is diminished. When the shot ceases to move, stop the 

 watch and note the time taken for the blood to clot. Repeat. 



Fig. 110. — Deiiniiisx- Watson cliiiiral visr-osiinctrr 

 (Iliiirk-yh'H). 



