EED BLOOD CORPUSCLES 



69 



young robust persons the number may be considerably higher. 

 The number may also be much reduced by considerable hemor- 

 rhages or by the imbibition of large quantities of fluid. Profuse 

 perspiration tends to produce concen- 

 tration of the blood and an apparent 

 increase in the number of its corpuscles. 

 The number of red blood cells in the 

 female is slightly less than in the male, 

 about 4,500,000 per cubic millimeter. 



The red blood cell consists of a com- 

 pound of hemoglobin with a colorless 

 mass, the "stroma" of Rollett. The 

 precise manner in which the hemo- 

 globin is contained within this stroma 

 has been the subject of considerable 

 discussion. The recent investigations 

 of G. K. Stewart * on the effect of lak- 

 ing reagents on the blood would tend 

 to show that the hemoglobin is in part 

 held in solution in the stroma, and in 

 part in more intimate combination. 

 That this stroma is not, as Rollett sup- 

 posed, a structureless mass, may now 

 be considered as satisfactorily demon- 

 strated. Much evidence lately ad- 

 vanced tends to show that the red cell, 

 though not possessed of a distinct cell 

 membrane in the sense of Schwann, is 



nevertheless supplied with an external limiting layer, a thickened 

 exoplasm, which is homogeneous in appearance, is insoluble in 

 water, permits free osmotic currents, and probably contains the 

 traces of lecithin and cholesterin which are found in the red 

 blood cells. 



Important information concerning the internal structure of 

 the stroma is furnished by the fact that the large nucleated red 

 blood cells of amphibians, as well as the early nucleated cells, 

 erythroblasts, of man and mammals, have been shown to possess a 

 reticular or alveolar structure. However, the living red blood cells 

 of human blood under ordinary conditions show no trace of inter- 



FIG. 74. BLOOD CELLS FROM A 

 SPECIMEN OF FRESHLY DRAWN 

 UNSTAINED HUMAN BLOOD. 



A, red blood cells, deep focus, 

 showing a light center and dim 

 margin ; B, the same with a high- 

 er focus ; the center, being slightly 

 out of focus, is dim while the 

 margin is light; (7, crenated red 

 cells from the margin of the prepa- 

 ration ; a, deep focus ; 6, higher 

 focus ; D, two polynuclear leuco- 

 cytes ; E, large mononuclear leu- 

 cocyte, x 750. 



* J. of Physiol., 1899 ; also J. of Med. Research, 1902. 



