MICROSCOPIC STRUCTURE OF THE BLOOD. 



279 



The finger is pricked and the blood which is to be examined is 

 drawn up into a tube provided for that purpose. The blood is 

 then put into the second compartment, which is afterward filled 

 with distilled water. The milled head /is then turned, and this 

 carries along with it the wedge of glass. W nen tne colors, as 

 seen by transmitted artificial light, in the contents of both com- 

 partments correspond, the percentage of hemoglobin in the blood 



FIG. 149. Von Fleischl's hemometer: a, stand;. 6, narrow wedge-shaped piece 

 of colored glass fitted into a frame (c), which passes under the chamber ; d, hollow 

 metal cylinder, divided into two compartments, which hold the blood and water ; 

 e, white plate from which the light is reflected through the chamber; /, screw 

 by which the frame containing the colored glass is moved ; g, capillary tube to 

 collect the blood ; h, pipet for adding the water ; i, opening through which may 

 be seen the scale indicating percentage of hemoglobin. 



may be ascertained by reading the scale at i. This instrument 

 should be used in a dark room. 



Oxy hemoglobin. It is this substance which gives to arterial 

 blood the scarlet color which is so characteristic of it ; here, how- 

 ever, it occurs, not by itself, but together with hemoglobin (re- 

 duced hemoglobin) and in excess of the latter. In venous blood 

 the two also coexist, but the hemoglobin is in excess, while in 

 the blood of asphyxia the coloring-matter is almost entirely 

 hemoglobin. 



