46 CHEMICAL PHYSIOLOGY. 



quite level with the top of the cylinder. Fill the other 

 compartment (a), that for the blood, about one-quarter with 

 distilled water. 



(b.) Prick the finger as in 8 with the instrument supplied 

 for the purpose. Fill the short automatic capillary pipette 

 tube with blood. Its capacity is 6 - 5 c.mm. In filling the 

 tube, hold it horizontally. See that no blood adheres to the 

 surface of the tube. This can be done by having the pipette 

 slightly greasy on the outer surface. 



(c.) Dissolve the blood obtained in (b.) in the water of 

 the blood-compartment (a'), washing out every trace of blood 

 from the pipette. Mix the blood and water thoroughly. 

 Clean the pipette. Then fill the blood-compartment exactly 

 to the surface with distilled water, seeing that its surface 

 also is perfectly level. 



(d.) Arrange a lamp in front of the reflector (S) which is 

 white, and with a smooth matt surface made of plaster-of- 

 Paris so as to throw a beam of light vertically through both 

 compartments. Look down vertically upon both compart- 

 ments, and move the wedge of glass by the milled head (T) 

 until the colour in the two compartments is identical. Read 

 off the scale, which is so constructed as to give the per- 

 centage of haemoglobin. 



