244 CIRCULATING FLUIDS: 



In cases where no consistent clot is formed, bnt where there 

 is merely a slight gelatinous coagulation, as frequently occurs 

 in blood deficient in fibrin, the serum and the clot cannot be 

 separated with any degree of exactness. If the clot be allowed 

 to stand for some hours in order to induce a more perfect se- 

 paration of the serum, the water partially evaporates, and the 

 ratio of the solid constituents of the clot to the water becomes 

 changed, and consequently too high a number is assigned to 

 the corpuscles. The difficulty of thoroughly remo\dng the water 

 varies in a direct proportion with the quantity of the blood 

 submitted to evaporation. Serum, comparatively poor in solid 

 constituents, gives only a slight residue, from which the water 

 can be more readily expelled, than from the more abundant 

 residue left by the clot : in proportion to the water remaining 

 in the clot, the quantity of corpuscles found by this method 

 will be increased^ as wiU be clearly seen by the following 

 illustration. 



1000 parts of blood are composed of 500 parts of serum and 

 500 of clot. 



The serum leaves a solid residue of 50, or 10^; the clot of 

 150, or 30;;. 



The 350 parts of water in the clot are to be estimated as 



serum, and thus give a residue of 35 parts; so that 1000 parts of 



bloodj (the fibrin not being taken into consideration) consist of: 



Water 800 



Solid residue ... 200 



Blood-corpuscles . . . 115 



Residue of serum ... 85 



If, however, the clot had not been perfectly dried, and if 

 only 1 per cent, of water in relation to the weight of the whole 

 blood had been retained^ we should have obtained the follow- 

 ing result : 



500 parts of clot would then give 160 of sohd residue, and 



there would therefore be 340 of water, which, estimated as 



serum, would yield 34 of residue ; consequently the corpuscles 



would be estimated at 126, and 1000 parts of blood would 



consist of: 



Water 790 



Solid residue . . . 210 



Blood-corpuscles . . . 126 



Residue of serum ... 84 



