70 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



Later on add a few drops of a 2 per cent, solution of calcium chlorid. 

 Does this blood clot? Explain. 



Draw blood into one-quarter of its volume of a saturated solution 

 of magnesium sulphate. Give a reason for its remaining fluid. 



Thoroughly cleanse the glass cannula, and connect.it with a short 

 curved tube. Allow blood to enter this tube until the air has been 

 expelled from it. Then dip the tube into a receptacle filled with mer- 

 cury and allow a small quantity of blood to collect over mercury con- 

 tained in a narrow vessel. Does this blood which has not come in con- 

 tact with air clot? 



Annotation. Air is not an essential factor in the coagulation of the blood, and 

 hence a perfect clot is obtained under this condition. 



Draw a small quantity of blood into a test-tube. Add a few drops 

 of distilled water. Note the changes in the color and general appear- 

 ance of this blood. Give their cause. Blood so hemolyzed is known as 

 laked blood. 



To a thin layer of blood collected upon a slide add a drop of a solu- 

 tion of bile salts. Note under the microscope the rapid destruction of 

 the red corpuscles. 



To another layer of blood add a drop of a hypertonic solution of 

 sodium chlorid. Study under the microscope the abnormal types of 

 red cells. Make sketches of them in different stages of crenation. 



4. Relative Amounts of Plasma and Corpuscles. Collect 30 c.c. 

 of blood in a test-tube. Immediately place it in the centrifuge opposite 

 a test-tube of the same size filled with water. Centrifugalize for a 

 period of five minutes. What is the proportion of plasma and cor- 

 puscles? 



5. Enumeration of the Red Corpuscles. Collect a drop of blood in 

 a watch-glass. Dip into it the end of a counting pipet (Thoma-Zeiss) 

 and aspirate gently upon the rubber tube until the pipet has been filled 

 with blood to line 1. Quickly cleanse its end with a piece of filter- 

 paper and dip it into Hay em's fluid. Aspirate until the bulb of the 

 pipet has been filled to line 101. Shake the tube well. Allow a drop 

 or two of this mixture to escape and place the next one upon the raised 

 base of the counting chamber. Do not allow it to overflow into the 

 space next to the base. Replace the cover, and determine under the 

 microscope the number of red cells in 20 squares. Take the average 

 and multiply this figure by 100 and 4000. 



Annotation. Since each square covers an area of 4^7 sq. mm. and has a capacity 

 of 4tVo c.mm., 1 c.mm. must contain 4000 times the average number found in these 

 squares. Moreover, since the dilution is 1 : 100, the number of red corpuscles in 1 

 c.mm. of blood must correspond to the number of red cells in a square X 4000 X 100. 



Hayem's fluid contains 2 grams of sodium chlorid, 10 grams of sodium sulphate, 

 1 gram of corrosive sublimate, and 400 grams of water. 



The pipet is cleaned by drawing distilled water through it, then alcohol, and 

 lastly ether. A current of air is passed through it from a rubber bulb until dry. 



