38 PREPARATION OF PLASMA. 



the presence of the fibrin-factors, the chemical composition of plasma 

 and serum is the same. 



[When blood coagulates, the following rearrangement of its elements takes 

 place : 



BLOOD. 



Plasma. Corpuscles, \ re , :, 



. j white. 



A __ 



I I 



feerum. Fibrin. 



u- 



I 



Fibrin, Corpuscles, and some Serum (Blood Clot).] 



The serum, however, still contains a portion of the fibrin-ferment, 

 and also some of the fibrino-plastin or fibrino-plastic substance. 

 Plasma is a clear, transparent, slightly thickish fluid, which, in most 

 animals (rabbit, ox, cat, dog), is almost colourless; in man it is 

 yellow, and in the horse citron-yellow. 



26. Preparation of Plasma. 



(A.) Without Admixture. Taking advantage of the fact that 

 plasma, when cooled to outside the body, does not coagulate for a 

 considerable time, Briicke prepares the plasma thus: Selecting the 

 blood of the horse (because it coagulates slowly, and its corpuscles sink 

 rapidly to the bottom), he receives it, as it flows from an artery, in a 

 tall narrow glass, placed in a freezing-mixture, and cooled to 0. The 

 blood remains fluid, and, the coloured corpuscles subsiding in a few 

 hours, the plasma remains above as a clear layer, which can be removed 

 with a cooled pipette. If this plasma be then passed through a cooled 

 filter, it is robbed of all its colourless corpuscles. 



[Burdon-Sanderson uses a vessel consisting of three compartments 

 the outer and inner contain ice, while the blood of the horse is 

 caught in the central compartment, which does not exceed half-an-inch 

 in diameter.] 



The quantity of plasma may be roughly (but only roughly) estimated 

 by using a tall, graduated measuring-glass. If the plasma be warmed, 

 it soon coagulates (owing to the formation of fibrin), and passes into 

 a trembling jelly. If, however, it be beaten with a glass-rod, the 

 fibrin is obtained as a white stringy mass, adhering to the rod. The 

 quantity of fibrin in a given volume of plasma is about 0'7 1 pel- 

 cent., although it varies much in different cases. 



