THE CIRCULATING LIQUIDS OF THE BODY 27 



the corpuscle than in its centre, but continuous throughout 

 its whole mass (Rollett). The denser peripheral layer con- 

 stitutes a physiological envelope which permits the passage 

 of certain substances into or out of the corpuscles, and 

 hinders the passage of others. 



Envelope and spongework are sometimes spoken of as the 

 stroma of the corpuscle, in contradistinction to its most 

 important constituent, a highly complex pigment, the 

 haemoglobin, which, not in solution as such, but either in 

 solution as a compound with some other unknown sub- 

 stance, or bound in some solid or semi-solid combination 

 to the stroma, fills up the whole space within the envelope 

 and all the interstices of the spongework. To the physical 

 properties of the stroma it is usual to attribute the great 

 elasticity of the corpuscles that is, the power of recovering 



FIG. i. DIAGRAM SHOWING RELATIVE SIZE OF RED CORPUSCLES OF VARIOUS 



ANIMALS. 



their original shape after distortion for their elasticity is no 

 wise impaired by the removal of the haemoglobin. 



When blood with disc-shaped corpuscles is shed, there is 

 a great tendency for the corpuscles to run together into 

 groups resembling rouleaux, or piles of coin. No satisfactory 

 explanation of this curious fact has yet been given. 



Crenation of the corpuscles, a condition in which they 

 become studded with fine projections, is caused by the 

 addition of moderately strong salt solution, by the passage 

 of shocks of electricity at high potential, as from a Leyden 

 jar, by simple exposure to the air, and in poisoning with 

 Calabar bean. Concentrated saline solutions, which abstract 

 water from the corpuscles and cause them to shrink, make 

 the colour of blood a brighter red, because more light is 

 now reflected from the crumpled surfaces. On the other 



