242 THE BLOOD 



The erythrocytes are the carriers, submerged barges into which 

 are packed the oxygen for the tissues and the carbon dioxide from 

 the tissues. 



Number. In health, a man has about 5,000,000 of these 

 corpuscles per cubic millimetre of blood. 



Shape. Mammals (except Camelidae) have circular biconcave 

 discoids. The camels have elliptical biconvex corpuscles. 



Size. Human corpuscles have a fairly constant diameter of 

 about 7 to 8 micro-millimetres. 



Colour. Individual corpuscles appear pale yellow, but in bulk 

 they appear red. 



Structure. The pigment is enclosed in a fine sponge-work of 

 lipoid nature which also forms the covering membrane of the 

 corpuscle. This membrane is elastic, allowing the corpuscles to 

 elongate in passing along capillary vessels. 



History. Erythrocytes are born in the red bone marrow. The 

 young corpuscle is called an erythroblast and has a nucleus. It 

 may live and die in its place of origin. In that case the valuable 

 constituent of the pigment, the iron, is retained by the marrow 

 and used in the construction of other cells. Most of the cells, 

 however, do not remain in the bone marrow. Their nuclei 

 atrophy and the enucleated corpuscles are shot into the blood 

 stream on their way to the liver, the crematorium of the body, 

 where they are alleged to be destroyed after 10 to 14 days. Those 

 which die by the way are taken out of the circulation by the 

 spleen. Economical Nature in this way makes use of the dying 

 erythrocyte as a beast of burden. 



Viscosity of whole blood. 



The presence of corpuscles prolongs the time taken by whole 

 blood to traverse a viscosimeter as compared with plasma. The 

 following figures show this. Serum was used instead of plasma, 

 to prevent complications by clot formation. 



TABLE XXXIV. 



Viscosity at 32 C. 



Serum + Corpuscles 1-9 



+ 3-2 xlO 6 3-3 



+ 6-3 xlO 6 - 4-9 



+12-6xl0 6 15-6 



The last high value was due to the mechanical blocking of the 

 capillary tube by the corpuscles which tend to agglutinate when 

 so concentrated. 



