THE FORMED CONSTITUENTS OF THE BLOOD 



153 



B. THE WHITE CORPUSCLES 



These are colorless, nucleated cells. Some varieties of them, at least, have, 

 like the free-living amcebw, the power to move independently from one place 

 to another by the protrusion of pseudopodia. On account of this very remark- 

 able property they probably play a very important role in many processes 

 of the body, although this role is not yet 

 sufficiently well known. Their activity is 

 entirely independent of the nervous system 

 and is controlled, in great part at least, 

 by chemotactic influences (cf. page 54). 

 Their general function, so far as investi- 

 gation has yet been able to determine, is 

 to provide for the transportation of vari- 

 ous substances inside the body and to 

 destroy or to remove foreign substances 

 from the body. 



The number of white corpuscles shows 

 considerable variation under normal cir- 

 cumstances, a fact dependent in part at 

 least on their entrance into or withdrawal 

 from the blood stream in greater or less 

 numbers. (Concerning the multiplication 



of white blood corpuscles appearing in digestion cf. Chapter VIII.) In the 

 adult the average number is 8,000 to 9,000 per cu. mm. i. e., one white to 

 every 500 to 600 red corpuscles. In the newborn the leucocytes are much 

 more numerous and reach on the average 18,000 per cu. mm. 



The white corpuscles are formed in extrauterine life chiefly in the spleen 

 and lymphatic glands: from these issue mononuclear cells (lymphocytes} which, 

 according to some authors, are transformed into polynuclear cells in the blood 

 stream. Moreover they exhibit a variety of forms and are divided according to 

 their appearance and staining reactions into several groups (see text-books of 

 histology). 



FIG. 49. Hsemin crystals, after 

 Preyer. 



C. THE BLOOD PLATELETS 



Discovered by Hayem (1877) and demonstrated in the circulating blood 

 by Bizzozero and Laker, the blood platelets are spherical or ellipsoidal bodies 

 which send out in all directions processes of variable number and length, 

 composed of the same shiny material as the body. According to the investi- 

 gations of Deetjen, Dekhuyzen and others, they have the full value of cells, 

 consist of nucleus and protoplasm, and are capable of amoeboid movement. 

 Their size varies between 0.005 and 0.0055 mm. Their number, according 

 to Brodie and Russel, amounts to about 635,000 in 1 cu. mm. of blood. With 

 respect to their chemical constitution it is especially emphasized that they 

 contain a nuclein body coupled with proteid ; and with respect to their physio- 

 logical purpose it is assumed by several authors that they play an essential 

 part in the coagulation of the blood. Their origin is as yet conjectural. 



