STRUCTURE AND FUNCTIONS OF BLOOD AND LYMPH 297 



analysis goes, then, each corpuscle is homogeneous throughout. 

 By other means we can, however, show that at least two materials 

 enter into the structure of each red corpuscle. If the blood be 

 diluted with several times its own bulk of water and examined 

 with the microscope, it will be found that the formerly red cor- 

 puscles are now colorless and the plasma colored. The dilution 

 has caused the coloring matter to pass out of the corpuscles and 

 dissolve in the liquid. This coloring constituent of the corpuscle is 

 hemoglobin, and the colorless residue which it leaves behind and 

 which swells up into a sphere in the diluted plasma is the stroma. 

 In the living corpuscle the two are intimately mingled through- 

 out it, and so long as this is the case the blood is opaque; but 

 when the coloring matter dissolves in the plasma, then the blood 

 becomes transparent, or, as it is called, laky. The difference may 

 be very well seen by comparing a thin layer of fresh blood diluted 

 with ten times its volume of ten per cent salt solution with a 

 similar layer of blood diluted with ten volumes of water. The 

 watery mixture is a dark transparent red; the other, in which the 

 coloring matter still lies in the corpuscles, is a brighter opaque red. 



Red corpuscles do not possess nuclei; they are not, therefore, 

 living cells in the ordinary sense. Whether they contain any 

 living protoplasm cannot be told certainly. So far as we can 

 judge their activities they are purely mechanical and do not re- 

 quire the participation of living substance. 



Consistency. Each red corpuscle is a soft jelly-like mass which 

 can be readily crushed out of shape. Unless the pressure be such 

 as to rupture it, the corpuscle immediately reassumes its proper 

 form when the external force is removed. The corpuscles are, 

 then, highly elastic; they frequently can be seen much dragged 

 out of shape inside the vessels when the circulation of the blood is 

 watched in a living animal (Chap. XX), but immediately spring- 

 ing back to their normal form when they get a chance. 



Composition. In the fresh moist state there are in 100 parts 

 of red corpuscles 57 to 64 of water and 36 to 43 of solids. Of the 

 solids nearly ninety per cent is hemoglobin, about one per cent 

 inorganic salts, chiefly phosphates and chlorides of potassium, the 

 residue the proteins and other materials of the stroma. 



Number. There is considerable variation in the number of red 

 corpuscles in any given volume of the blood. The average for the 



