COAGULATION OF THE BLOOD. 23 



per thousand. The proportion of dried fibrin is about three parts per 

 thousand. 



After the extraction of plasmine from the blood, another coagulable sub- 

 stance remains, which is called serine. This is coagulated by heat, the strong 

 mineral acids or absolute alcohol, but is not coagulated by ether, which 

 coagulates egg-albumen. Serine bears a close resemblance to ordinary albu- 

 min but is much more osmotic. Its proportion, desiccated, in the blood is 

 about fifty-three parts per thousand. 



Peptones etc. A certain quantity of nitrogenized matter, distinct from 

 the constituents just described, has been extracted from the blood, which is 

 analogous to peptone. This is separated by coagulating the serum of the 

 blood with hot acetic acid and filtering, when the peptones pass through in 

 the filtrate. These substances are probably derived from the food. Their 

 proportion in the plasma is about four parts, dried, per thousand, or twenty- 

 eight parts before desiccation. 



A small quantity of coloring matter exists in the plasma. If the corpus- 

 cles be separated as completely as possible, the clear liquid still has a reddish- 

 amber color. This coloring matter has never been isolated and studied. It 

 is analogous to the coloring matter of the .red corpuscles, the bile and the 

 urine. 



In addition to the organic nitrogenized constituents which have just been 

 described, some physiological chemists recognize a substance called para- 

 globuline, or fibrinoplastic matter, and fibrinogenic matter. These are sup- 

 posed to be factors of fibrin, which come together in the coagulation of the 

 blood. They will be considered in connection with the theories of coagula- 

 tion. The so-called sodium and potassium albuminates have not been posi- 

 tively established as normal constituents of the blood. 



COAGULATION OF THE BLOOD. 



The blood retains its fluidity while it remains in the vessels and circula- 

 tion is not interfered with, and is then composed of a clear plasma holding 

 corpuscles in suspension. Soon after the circulation is interrupted or after 

 blood is drawn from the vessels, it coagulates or " sets " into a jelly-like mass. 

 In a few hours, contraction will have taken place, and a clear, straw-colored 

 fluid expressed, the blood thus separating into a solid portion, the crassa- 

 mentum, or clot, and a liquid which is called serum. The serum contains 

 all the constituents of the blood except the corpuscles and fibrin-factors, 

 which together form the clot. Coagulation takes place in the blood of all 

 animals, beginning a variable time after its removal from the vessels. In the 

 human subject, when the blood is received into a moderately deep, smooth 

 vessel, the phenomena of coagulation present themselves in the following 

 order : 



First, a gelatinous pellicle forms on the surface, which occurs in one 

 minute and forty-five seconds to six minutes ; in two to seven minutes, a 

 gelatinous layer has formed on the sides of the vessel ; and the whole mass 

 becomes of a jelly-like consistence, in seven to sixteen minutes. Contraction 



