BLOOD 195 



ment from destroyed corpuscles. Sometimes a 'stippling' or granule 

 formation occurs within the corpuscle, which has been ascribed to degenera- 

 tion of the haemoglobin. The dissolution of red corpuscles is known 

 as hamolysis and follows the injection of certain poisonous substances 

 into the blood. It occurs in various diseases. The study of the effects 

 of mixing the blood of one species of animal with that of another, has pro- 

 vided a very perfect means of distinguishing the species from which a 

 blood stain of unknown origin may have been derived. 



WHITE CORPUSCLES. The white corpuscles or leucocytes are thoset 

 blood cells which retain their nuclei and do not contain haemoglobin.! 

 The youngest stages of erythroblasts, according to this definition, are 

 leucocytes, and like other leucocytes they are derived from the mesoderm. 

 In 1890 Howell wrote, "Before 1869 it was quite generally believed that 

 the red corpuscles are formed from the white corpuscles in fact, some 

 of the most recent investigations favor this view, although the evidence 

 is so overwhelmingly against it." It is still advocated by foremost in- 

 vestigators of the blood, and is referred to as the " monophyletic theory." 

 Those who believe in diverse origins of red and white corpuscles, and of 

 the various forms of white corpuscles, support the "polyphyletic theory." 



Maximow (Arch. f. mikr. Anat., 1909, vol. 73, pp. 444-561) states that "the first 

 leucocytes, the lymphocytes, arise at the same time and from the same source as the 

 primitive erythroblasts; the latter represent a specially differentiated form of cell, but 

 the lymphocytes always remain undifferentiated. Therefore, like the primitive blood 

 cells from which they directly proceed, they are undifferentiated rounded amoeboid 

 mesenchymal cells." Weidenreich (Anat. Rec., 1910, vol. 4, pp. 317-340) concludes 

 that "the old, original view of the unified genetic character of all blood cells proves to 

 be correct," and he regards the lymphocyte as the primitive or young form of white 

 corpuscles. (For many other references, see Minot, in Keibel and Mall's Human 

 Embryology, vol. 2.) 



Against the monophyletic interpretation, it has been asserted that the lymphocytes 

 of the adult are a different form of cell from the primitive blood cells, and that they are 

 not found in embryos until the time when lymph glands develop. These arise rather 

 late in rabbits of 25 mm. and in human embryos of 40 mm. (Lewis, Anat. Rec., 1909, 

 vol. 3, pp. 341-353). According to the polyphyletic view, the lymphocytes are first 

 formed from the reticular tissue in these glands and from similar tissue elsewhere. If 

 this is true, it becomes unnecessary to regard the lymph glands as organs for producing 

 young cells, and the bone marrow as an organ for producing old cells. The relation of 

 these organs to blood formation will be considered in a later chapter. 



The number of white corpuscles in a cubic millimeter of human blood 

 is about eight thousand. If it exceeds ten thousand the condition is called 

 leucocytosis and becomes of clinical importance. There exists, therefore, 

 normally but one leucocyte for five or six hundred red corpuscles. In 

 the circulating blood the two sorts are said not to be evenly mixed; the 

 leucocytes are more numerous in the slower peripheral part of the blood 

 stream, near the endothelium. The leucocytes may be divided into three 



