SECTION II 

 THE RED BLOOD-CORPUSCLES 



THE red blood-corpuscles, or erythrocytes, in man and in mammals 

 are nucleated bi-concave discs, about 7 to SJUL (-%-%-Q ^ in.) in diameter 

 and about one- third of this in thickness. The colour of a single 

 corpuscle when viewed under the microscope is yellow, the red colour 

 being only apparent when larger numbers are seen together. The 

 red corpuscles form about 50 per cent, of the total mass of the blood, 

 there being about 5,000,000 red corpuscles in every cubic millimetre 

 of blood. They are soft, flexible, and elastic, so that they can 

 readily squeeze through apertures and canals narrower than them- 

 selves without undergoing permanent distortion. Each red corpuscle 

 consists of a framework or stroma, composed chiefly of protein 

 material, containing in its meshes or in a state of loose chemical 

 combination a red colouring-matter, haemoglobin, to which is due the 

 colour of the corpuscles and of the blood itself. 



It is only in mammalia that the red corpuscles are of the character 

 described. In the camel they are oval in shape, but otherwise resemble 

 the corpuscles of other mammals. In all other classes of vertebrata 

 the red corpuscles are oval, nucleated cells. The haemoglobin is 

 diffused through the protoplasm of the cell-body and does not extend 

 to the nucleus. During the early part of foetal life the corpuscles of 

 mammals are also nucleated, but in the adult condition the erythro- 

 cytes, except under abnormal conditions, lose all traces of the nucleus 

 before entering the blood stream. The small size and great number of 

 the red corpuscles determine that a very large area of surface of red 

 corpuscles is exposed to the plasma. The volume of each corpuscle has 

 been estimated as -0000000722 mm. 3 , and its surface as -000128 mm. 2 , 

 so that the total surface of red corpuscles in the blood of a man 

 weighing about 70 kilos (assuming his total blood as -^ s of the body 

 weight) would be about 3000 sq. metres, or 1500 times the surface of 

 the body itself. This great extent of surface is of importance in 

 facilitating the exchange of material, especially oxygen, between the 

 corpuscle itself and the surrounding plasma. 



On treating the blood with weak solutions of tannic or boracic 

 acid a separation occurs between the haemoglobin and the stroma, the 

 former appearing as a small ball near the centre of a colourless disc 



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