CHAPTER IV. 

 THE BLOOD. 



THE blood is to be considered from a certain standpoint as a 

 fluid tissue, and it consists of a transparent liquid, the blood- 

 plasma, in which an immense number of solid particles, the red 

 and colorless blood-corpuscles (and the blood-tablets) are suspended. 



Outside of the organism the blood, as is well known, coagulates 

 more or less quickly; but this coagulation is accomplished gener- 

 ally in a few minutes after leaving the body. All varieties of blood 

 do not coagulate with the same degree of rapidity. Some coagulate 

 more quickly, others more slowly. Among the varieties of blood 

 thus far investigated the blood of the horse coagulates most slowly. 

 The coagulation may be more or less retarded by quickly cooling; 

 and if we allow equine blood to flow directly from the vein into a 

 glass cylinder which is not too wide and which has been cooled, 

 and let it stand at C., the blood may be kept fluid for several 

 days. An upper, amber-yellow layer of plasma gradually separates 

 from a lower, red layer composed of blood-corpuscles with only a 

 little plasma. Between these we observe a whitish-gray layer, 

 which consists of white blood-corpuscles. 



The plasma thus obtained and filtered is a clear amber-yellow 

 alkaline liquid which remains fluid for some time when kept at 

 C., but soon coagulates at the ordinary temperature. 



The coagulation of the blood may be prevented in other ways. 

 After the injection of peptone or, more correctly, albumose solu- 

 tions into the blood (in the living dog), the blood does not 

 coagulate on leaving the veins (FANO, SCHMIDT-MULHEIM). The 

 plasma obtained from such blood by means of centrifugal force is 

 called "peptone-plasma." The coagulation of the blood of warm- 



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