WHITE BLOOD CELLS 81 



give characteristic absorption bands. The spectrum of a dilute 

 solution of oxyhemoglobin shows two dark bands, both between 

 the lines D and E. That nearer the red end of the spectrum, 

 or alpha band, as it is called, is darker, narrower, and more 

 distinct than the other, or beta band. The distinctness and 

 width of the bands vary with the density of the solution. With 

 very dilute solutions only a faint alpha band is present; with 

 stronger solutions the bands grow wider, fuse, and finally shut 

 off all light. The orange is the last to disappear. If a solution 

 of oxyhemoglobin is converted to reduced hemoglobin by the 

 addition of Stokes' reagent (an ammoniacal solution of a ferrous 

 salt), only one absorption band is seen, called the gamma band, 

 which lies between the lines D and E. 



The length of life of a red blood corpuscle is not known. Since 

 hemoglobin forms the mother substance of the bile pigments 

 which are continually being passed from the body, and also 

 since the corpuscles are non-nucleated, it is believed that they 

 are continually undergoing disintegration in the bloodvessels. 

 They are replenished by special corpuscle-forming or hema- 

 topoietic tissues, the process of production being known as 

 hematopoiesis. The red marrow of the bones is the most marked 

 example of such tissue. Here groups of nucleated colorless 

 cells known as erythroblasts undergo karyokinesis, and the 

 daughter cells, after forming hemoglobin in their cytoplasm, 

 are nucleated corpuscles which in time extrude their nuclei 

 and are forced by the growing tissue into the blood stream. 

 In the embryo the liver and the spleen also produce new red 

 corpuscles. 



White Blood Cells. These are variously classified. Ehrlich 

 makes three divisions oxyphiles or eosinophiles , whose granules 

 are stained with acid stains; basophiles, which stain only with 

 basic stains; and neutrophiles, which stain only with neutral 

 dyes. 



A simpler classification may be made : 



1. Lymphocytes , small, having a round vesicular nucleus and 

 scanty cytoplasm. 



2. Mononuclear leukocytes, large, having a vesicular nucleus 

 and abundant cytoplasm. 



3. Poly nuclear leukocytes, large, with nucleus divided_intQ 

 lobes or into distinct parts, 



6 



