CH. XXVI. 1 



RED BLOOD-CORPUSCLES. 



415 



cent, by weight of the whole mass of the blood. The proportion 

 of colourless corpuscles is only as i to 500 or 600 of the coloured. 

 Red or Coloured Corpuscles. Human red blood corpuscles 

 are circular biconcave discs with rounded edges, ^^Vo" inch in 

 diameter (j/x to 8/1) and y^o-jr inch, or about 2/u., in thickness. 

 When viewed singly they appear of a pale yellowish tinge ; the 

 deep red colour which they give to the blood is observable in 

 them only when they are seen en masse. They are composed 

 of a colourless, structureless, and transparent filmy framework, 

 or stroma, infiltrated in all parts by a red colouring matter 



Fig. 342. Red corpuscles in rouleaux. 

 The white corpuscle* are uncoloured. 



Fig. 34 <. Corpuscles of the frog. The 

 central mass conxists of nucleated 

 coloured corpuscles. The other cor- 

 puscles are two varieties of the 

 colourless form. 



termed haemoglobin. The stroma is elastic, so that as the cor- 

 puscles circulate they admit of changes of form, in adaptation 

 to the vessels, and recover their natural shape as soon as they 

 escape from compression. The colouring matter uniformly per- 

 vades the stroma. The consistency of the peripheral part of the 

 stroma is greater than that of the more central portions ; this 

 plays the part of a membrane in the processes of osmosis that 

 occur when water or salt solution are added to the corpuscles. 



The red corpuscles have no nuclei ; the unequal refraction of 

 transmitted light gives the appearance of a central spot, darker 

 or brighter than the border, accord ing an it is viewed in or out 

 of focus. Their specific gravity is about 1088. 



The corpuscles of all mammals, with the exception of the 

 camel tribe, are circular and biconcave. They are generally very 

 nearly the ni/,e of human red corpuscles. Tluey are smallest in 



