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 8^ (^o~TT * n -) * n 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 

 themselves 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, hemoglobin, 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 f cetal life the corpuscles of mammals are also nucleated, but 

 in the adult condition the erythrocytes, 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 -^ 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 or being extruded 

 so as to he just outside the stroma. Briicke, who first observed this appear- 

 ance, gave the name of ' zooid ' to the mass of haemoglobin and of ' oecoid ' 

 to the stroma. 



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