OPTICAL PROPERTIES OF BLOOD. 



237 



out the draw tube until the light is properly focused and observe that the 

 bright field is traversed by two black bands which cut out portions of the 



3'ellow and green. With strong blood solutions all light except red is shut 

 out, but with solutions of the dilutions 2 to 7 the field is obscured only 

 Tby the two bands. In solution No. 2 they are very dark and well defined. 



