264: THE BLOOD. 



The coagulation of fibrine is not a commencement of -organization. 

 It is simply the passage of an albuminous ingredient of the blood from 

 its normal fluid condition to a state of solidity. The coagulable ingre- 

 dient of the blood, when solidified, has lost its natural properties as a 

 constituent of the liquid plasma, and cannot afterward be restored to 

 its original condition. The clot, therefore, when once formed, even in 

 the interior of the system, as in cases of ligature, apoplexy, or extrava- 

 sation, becomes a foreign body, and is reabsorbed by the neighboring 

 parts during convalescence. At first the clot is comparatively volumi- 

 nous, soft, and of a deep red color. Its more fluid parts are then reab- 

 sorbed, and the clot becomes smaller and denser. The red coloring 

 matter gradually diminishes as absorption goes on, and finally altogether 

 disappears. The time required for complete reabsorption varies from a 

 few days to several months, according to the size of the clot and the 

 situation in which extravasation has taken place. 



Nature of the Process of Coagulation. The difficulty in fully under- 

 standing the nature of coagulation depends upon the fact that the blood 

 naturally continues fluid under all ordinary conditions while circulating 

 in the vessels, but coagulates inevitably within a few minutes after its 

 removal. Properly speaking, the fibrine which we obtain at the time of 

 coagulation, either by itself or as forming a part of the clot, does not 

 pre-exist in the blood with the same constitution and properties, other- 

 wise it would coagulate within the vessels during life. It must be de- 

 rived from some ingredient of the blood, which, on being withdrawn from 

 the current of the circulation, suffers a change by which it becomes 

 spontaneously coagulable. It is not easy to understand what this 

 change may be, or what are the immediate influences which produce it. 



There are two theories in existence as to the nature of coagulation. 

 According to one of them (Denis), the coagulable fibrine is produced by 

 the spontaneous decomposition of a liquid substance pre-existing in the 

 blood. This substance is termed plasmine, and is thought to be present 

 in the plasma of the blood in the proportion of 25 parts per thousand. 

 When withdrawn from the circulation it decomposes or separates into 

 two new substances. One of these is fibrine (3 parts per thousand), 

 which immediately coagulates ; the other is metalbumen (22 parts per 

 thousand), which remains fluid. The basis of this theory is, that if 

 fresh blood be drawn into a concentrated solution of sodium sulphate, 

 as above stated, no coagulation takes place. But if sodium chloride in 

 powder be added to this mixture in the proportion of ten per cent., it 

 precipitates a white pasty substance, which is thrown down because it 

 is insoluble in a sodium chloride solution of that strength. This sub- 

 stance, the so-called " plasmine," represents 25 parts per thousand of 

 the original plasma. After its separation it may be readily dissolved 

 again by the addition of water; but in a few moments its solution coagu- 

 lates, yielding 3 parts of a solid matter like ordinary fibrine, and 22 

 parts of a liquid substance having the properties of metalbumen. The 

 albumen proper of the blood remains behind in the sodium sulphate 



