NORMAL HJEMATOLOGY 139 



The haemoglobin contains practically all the coloring matter, and 

 it constitutes 90 per cent, of the red cell. The haemoglobin consists of 

 96 per cent, globulin and 4 per cent, haematin. In the hsematin is 

 the iron of the corpuscles; the coloring matter of the blood varies 

 as does the amount of iron. Theoretically, the most accurate way 

 to test the haemoglobin would be to measure the amount of iron 

 in a certain amount of blood. But the chemical extraction and 

 weighing of so small an amount of iron is too difficult and tedious. 

 Because of this, other tests have been devised, which depend upon 

 the observer's eye to detect the likeness of shades of red as repre- 

 sented by the blood and colored glass, solutions or paper. Again, the 

 specific gravity of the blood except in rare cases depends upon the 

 amount of iron in the red cells, and varies as the iron does. Then 

 we can estimate the percentage of haemoglobin by finding the specific 

 gravity of the blood. 



The principal tests may be classified as follows: 



1. Estimation of iron in the blood. 



Jolles' ferrometer. 



2. Estimation of percentage of coloring matter by color tests. 



A. Fleischl's haemometer. 



B. Gowers' haemoglobinometer. 



C. Dare's haemoglobinometer. 



D. Tallquist's haemoglobinometer. 



3. Obtaining the specific gravity of the blood by Hammerschlag's 

 method. 



A. Fleischl's Haemometer. 



Appliances. Fleischl's haemometer; glover's needle; pasteboard 

 tube two inches in diameter; artificial light; small beaker; a dark 

 room or cupboard. 



Fleischl's haemometer consists of a sliding colored-glass wedge 

 which moves in a standard underneath a cylindrical metallic cup, 

 and a capillary tube. This cup is divided into two equal com- 

 partments and has a glass bottom and a detached glass top. The 

 capillary tube is very small and is held by a small metallic band on 

 a handle. The glass wedge and the capillary tube are the important 

 parts of the instrument and are made to be used together. There is 

 a number on the handle of the capillary tube, indicating its capacity, 

 and this same number is stamped on the top of the standard; also 

 a number is placed on the end of the sliding frame that holds the 

 glass wedge, and the same number appears on the base of the standard 

 of the instrument to which it belongs (Fig. 69). 



Reagents. Distilled water and hydrogen peroxide. 



Preparation. Clean metallic cell or well with water and dry with 

 a cloth only when it needs it. The capillary tube should be cleaned 

 with water and hydrogen peroxide, and then with water again, by 



