142 SPECIAL PHYSIOLOGY 



the capillary in the small space o the cell. Very gentle constan 

 waving back and forth or into the water and out is the most effectiv( 

 in getting the blood out of the tube. Too vigorous movements arc 

 liable to break the glass tube. When completing the filling of the 

 cells with water, fill the cell containing water only first, and ther 

 there is no danger of getting any of the diluted blood into the watei 

 compartment. If you neglect to stir the blood and water just befon 

 adjusting the glass cover the blood will remain in the lower part o: 

 the cup with the water on top, and it will have a darker colo] 

 than it should because the blood really is not diluted as necessary 

 This will give a higher reading than is accurate. The glass cove] 

 should always be used; it not only makes the amount of dilutior 

 accurate, but it gives an even surface for the transmitted light rays 

 Without the glass the surface of the water is either concave or convex 



The metallic cup should not be taken apart unless it is very dirty 

 If the glass is clean, that is sufficient. As a laboratory precaution 

 where several instruments are in use, always compare the marking! 

 to be sure that you have the capillary tube that goes with the glasi 

 wedge that you have. 



Questions. 1. Why use distilled water to dilute blood and not % 

 saline solution similar to the plasma of the blood? 



2. Name four common sources of error in the technique. 



3. Can different individuals make approximately the same reading 

 of the same test? 



4. Can different individuals make approximately the same results 

 from the same individual's blood? 



5. Does every individual in ordinary health have the same per- 

 centage of haemoglobin? 



6. How would you explain the variation, if any? 



7. Do individuals who have a low percentage of haemoglobin have 

 a correspondingly lessened number of red cells per cubic millimetre 1 



8. Is the reverse of the above true? 



B. Gowers' Hsemoglobinometer. 



Gowers' haemoglobinometer consists of three pieces: a capillary 

 measuring pipette, a graduated tube, and a sealed tube containing a 

 standard colored solution. The standard colored solution represents 

 the color of 1 per cent, solution of normal blood. The graduated 

 tube is marked in 100 or more parts, and each part represents 

 20 c.mm. The capillary pipette holds 20 c.mm. up to the mark on 

 the tube. If the blood is normal it will be necessary to add water 

 to the hundredth mark in order to make the colors correspond. If 

 the blood is not normal the percentage can be read off the graduated 

 tube at the top of the diluted blood when the colors correspond. 

 There are two kinds of instruments: one for use with daylight, 



