202 THE BLOOD 



bacteria. It is also possible to obtain large numbers of lymphocytes 

 from lymphatic glands. As will be explained more fully later on, 

 the pus-corpuscles are the remnants of destroyed leukocytes. They 

 show a content in water of 90 per cent. The solids (10 per cent.) 

 consist chiefly of albumin, globulin, nuclein, nucleoproteid and nucleo- 

 histon. Neutral fats appear in their cytoplasm as strongly refracting 

 granules. Cholesterin, lecithin, glycogen and alkaline phosphates 

 are also present. 



The Origin and Fate of the White Blood Corpuscles. — The different 

 views regarding the formation of the white corpuscles may be said to 

 advocate either a monophyletic or a dualistic origin. In accordance 

 with the former, the different varieties of white corpuscles are regarded 

 as having arisen from a single mother-cell.^ To be sure, the facts 

 favoring this unitarian mode of generation are insufficient, at least 

 when applied to the adult animal, but it is also true that the objections 

 commonly raised against it, lose much of their weight when the condi- 

 tions existing in the embryo are more fully considered. The dualistic 

 theory is based upon the contention that the lymphocytic white cells 

 arise from the so-called lymphoblasts which are present in the adenoid 

 tissue of the lymphatic glands and lymph nodules, and that the larger 

 ameboid types, or leukocytes, are descended from the myeloblasts of 

 the bone-marrow. This view, which was first expressed by Ehrlich, 

 is the most favored at the present time. 



The lymph nodule consists of a dark peripheral and a clear inner 

 zone, or germ center. The latter is formed by large cells which 

 divide and give rise to the lymphocytes. The largest number of these 

 then escape into the lymph channel situated at the periphery of the 

 nodule, but a few of them also enter the blood stream directly. Those 

 white corpuscles which originate in the marrow of the bones, have as 

 their precursors the so-called myelocytes which present themselves 

 as granular or non-granular protoplasmic masses with rounded nuclei. 

 By transition these elements finally assume the characteristics of the 

 leukocytes, and eventually escape into the blood capillaries of the 

 marrow, whence they are distributed to all parts of the body. 



The duration of the Hfe of these colorless corpuscles has not been 

 determined with accuracy. They undergo dissolution and disappear. 

 Many of them are destroyed while engaged upon their mission of 

 ridding the body of toxic substances. 



THE FUNCTION OF THE WHITE BLOOD CORPUSCLES 



Contractility and Motion. — A molecular movement of the cyto- 

 plasm has been observed in all white corpuscles, but with the exception 

 of the polynuclear and mononuclear varieties, this movement is not 

 sufficiently strong to cause motion. "White cells may be obtained 

 without much difficulty by placing a drop of blood upon a glass slide 

 1 Weidenreich, Ergebn. der Anat. und Entwickelungsgeschichte, xix, 1911, 2. 



