THE BLOOD AND THE LYMPH 



263 



plicated chemically these whole fluids are; we shall now see that their 

 physical structure is not less complex and admirable. 



Of whole blood about 45 per cent, by weight are corpuscles and 

 55 per cent, plasma. There are probably three sorts of corpuscles 

 at least in the blood and lymph, one of which three kinds may possibly 

 consist really of several varieties. The life-histories of the corpuscles is 

 not yet fully known with certainty. The functions of the various cor- 

 puscles are somewhat more definitely understood, but probably the leuko- 

 cytes and the thrombocytes at least have other uses in the economy than 

 those we can describe at present. These two are more or less ameboid, 

 and exhibit the versatility usual to little-differentiated (?) protoplasm. 

 All the corpuscles have been the subject of a very large amount of 

 research, but the two colorless sorts, owing partly perhaps to their 

 easy destructibility and to their relative fewness, have largely escaped 

 hitherto that direct observation which alone could give adequate knowl- 

 edge of their functions. 



FIG. 136 



Microscopic view of some erythrocytes : A, on flat; B, on edge. (Dalton.) 



ERYTHROCYTES, the colored plastids or corpuscles, are frequently 

 called red corpuscles because they give the blood its color. When seen 

 singly, or in single rouleaux, however, no redness is apparent, but, if any- 

 thing, besides a pale, straw-yellowness, a tinge of green. To the histolo- 

 gists the term erythrocyte indicates still the embryonic nucleated form 

 of these corpuscles. The erythrocytes constitute about 40 per cent, of 

 the weight of the whole blood. (See Plate VI.) 



In their structure only three elements have been made out: a very 

 delicate frame-work of transparent nucleo-proteid (globulin?) called 

 the stroma; 90 per cent, of hemoglobin, already described; and a clear, 

 glassy envelope of some gelatinous material, very thin and flexible 

 (Deetjen). The erythrocytes originate most likely by the division of 

 erythroblasts in the bones' red marrow and at first have nuclei. As 



