320 



THE BLOOD 



shrink and shrivel. They then break up into fragments, due to 

 inequahties in the tensile strength of the corpuscle. Most peculiarly 

 the first stage in exosmotic laking is a swelling of the corpuscle. 

 Some change in the physico-chemical state of the protein moiety 

 in the envelope is indicated. It has been shown that the power 

 of colloids to imbibe water may be altered by alterations in their 

 crystalloid content. 



Colligative properties of whole blood. 



The suspension of small bodies like blood corpuscles in plasma 

 should not materially affect the values of vapour pressure, osmotic 

 pressure, etc. This is found to be the case. Using average values 

 taken from Grollman's paper referred to above, we find that blood 

 has practically the same vapour pressure and osmotic pressure as 

 its plasma at body temperature. Plasma is, however, slightly 

 richer in free salts, as shown by a slightly greater depression of the 

 freezing point. The difference is so slight that one might hesitate, 

 in view of the unstable nature of the bound salts of " separated " 

 plasma, to accept it as significant. 



TABLE XLII 



Colligative Properties of Blood and "' Separated " Plasma 



AT 37-5° C. (Dog) 



* Calculated from vapour pressures. 

 XL, 1928. 



Grollman : Jour. Gen. Physiol., 



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. 



