494: THE BLOOD. 



coagulation may be accelerated by elevated tempera- 

 ture, violent motion, and by access of oxygen ; retarded 

 by saturation with carbonic anhydride, by the addition 

 of a small quantity of free potassa or ammonia, by a 

 number of alkaline salts, and by slight acidification 

 with acetic acid ; and, finally, entirely prevented by 

 the neutralization of the previously acidified blood 

 with ammonia; or, better, by allowing the blood to 

 flow directly from the vein into a concentrated solu- 

 tion of sodium sulphate. When blood is beaten while 

 flowing from the vein, the fibrin separates in stringy 

 masses, without inclosing a large amount of corpus- 

 cles, which, for the greater part, remain unchanged, 

 suspended in the serum. On account of the slimy 

 character of the latter, however, they cannot be sepa- 

 rated from it. If ten times its volume of a mixture 

 of one volume concentrated solution of sodium chlo- 

 ride and from nine to ten volumes water is added, and 

 the whole allowed to stand, the separation becomes 

 possible. TJiey then sink, the supernatant liquid can 

 be poured off, and the blood-corpuscles washed with a 

 solution of sodium chloride of the same strength as 

 that employed in the mixture. 



The red blood-corpusles of man and most mammalia 

 consist almost exclusively of a peculiar body, hcemato- 

 globulin or hcemoglobin, while in the blood-corpuscles of 

 birds and several mammalia, considerable quantities of 

 albuminous substances occur together with this. "When 

 free of albuminous substances, or when these are pre- 

 viously removed, the corpuscles crystallize, on the ad- 

 dition of water at a low temperature, in rhombic crys- 

 tals, only a very small quantity remaining dissolved 

 in the water. They can be purified by recrystalliza- 

 tion from water at a low temperature, if a little alco- 

 hol is added. After being dried over sulphuric acid 

 at a temperature below 0, they form a brick-red pow- 

 der, still containing 3-4 per cent, of water. When 

 this is dissolved in alcohol, and cooled, crystals are 

 again deposited. It decomposes very readily in the 

 presence of water. If an aqueous solution of pure 

 haemoglobin is allowed to stand for some time at the 



