CHAP. II.] 



THE BLOOD. 



35 



fibrin in the clot of human blood can be admirably and easily shewn 

 by- following the method also described by Ranvier. A pretty large 

 drop of human blood (obtained by pricking the finger) is treated as 

 was mentioned in the case of frog's blood. After some hours, the 

 paraffin is scraped off, the cover-glass is lifted, and the coagulum of 

 blood which adheres to the slide or cover-glass, or to both, is subjected 

 to the action of a gentle stream of water. Ranvier allows the water 

 to flow out of a pipette, but the Author finds that a very small stream 

 at very low pressure from a water tap is even preferable. After all 

 the red colour has disappeared, a drop of a strong solution of magenta 

 is placed upon the site of the former blood clot ; this is then covered 

 with a covering glass and examined. The preparation is then, seen to 

 be covered by reticula, each of which appears to radiate from a cen- 

 tral granulation. The granulations as well as the fibres are stained 

 by magenta and by solution of iodine, but not by carmine or picro- 

 carmine. These granulations will be further referred to in con- 

 nection with the part which the formed elements of the blood play 

 in its coagulation. 



Fro. 10. EETICULUM OF FIBRIN FROM: THE BLOOD OF MAN. 500 diain. (Eanvier.) 



Mode of Fibrin may be obtained either from blood or from 



separating liquor sanguinis, either by allowing these fluids to coagu- 

 Fibrin for late at rest, or by stirring them with twigs, or by agitating 

 chemical them with small pieces of metal or glass. The fibrin, obtained 

 examination. by stirring blood, adheres to the instrument employed; it 

 is at first deeply stained with blood, but by washing in a stream of 

 water it gradually loses its red colour and presents the appearance of 

 a white, stringy, elastic body. 



When obtained by the first method from plasma, the coagulum 

 at first presents a gelatinous appearance ; if, however, the coagulum 

 be placed in a cloth and be kneaded with water, as the serum is 

 squeezed out, there is left fibrin in the form of a white stringy solid. 



3-2 



