110 THE BLOOD. 



For clinical purposes a convenient instrument for the determi- 

 nation of the amount of haemoglobin in the blood is that of Fleischl, 

 called an haemometer. It consists of a short, vertical cylinder for 

 holding the blood, separated by a partition into two compartments; 

 a long movable wedge of ruby glass under one compartment for 

 a standard of color, and a white surface below for reflecting the 

 light up through the wedge and cylinder to the eye of the observer. 

 The amount of haemoglobin is found by filling one compartment 

 of the cylinder with diluted blood, and the other, over the ruby 

 prism, with water. The prism is then moved until the depth of 

 color is exactly the same as that of the blood, when the percentage 

 of haemoglobin compared with the normal amount can be read from 

 the scale. The following is the process: 



Use for a light a lamp or yellow gas-flame, not an incandes- 

 cent light or daylight. Any blood may be used for practice. In 

 clinical cases use that obtained from the tip of the finger by the 

 aid of a lancet. After making the incision force out a drop of 

 blood by gentle pressure. Measure off the required volume of blood 

 (6V 2 cubic millimeters) by filling the small glass tube, open at 

 both ends and mounted on a handle, which accompanies the 

 haemometer. This is accomplished by holding it horizontally and 

 dipping one end into the drop. Wipe carefully all blood from the 

 surface of the tube. This will be more readily done if the surface 

 of the tube is kept slightly greasy by being preserved in an oily 

 piece of chamois. The blood must exactly fill the tube, having 

 neither a convex nor a concave surface at the open ends. 



The compartment over the ruby-glass prism is to be filled 

 with distilled water by means of a pipette and the other one not 

 more than a quarter full. Into the latter the open glass measuring 

 tube is dipped before the blood has coagulated, and the haemoglobin 

 is dissolved by moving the tube back and forth so as to wash out 

 the blood. Then rinse off the tube into the blood solution by the 

 use of a few drops of water from the pipette. Fill the compart- 

 ment from a half to three-fourths full of water and stir well with 

 a wire or with the handle of the measuring tube. Mix the water 

 with the blood until no turbidity is seen and until it is evident 

 that the fluid in the angles is completely incorporated with the rest. 

 Now drop water from the pipette upon the blood solution until it, 

 as well as the water in the other compartment, comes exactly to 



