THE BLOOD. 159 
living body, coagulation has resulted in the formation of two 
new products—serum and fibrin—differing both physically and 
chemically. These facts may be put in tabular form thus: 
Blood as it flows ( Liquor sanguinis (plasma). 
in the.vessels. Corpuscles. 
Fibrin. 
Coagulum \ Corpuscles. 
Serum. 
Blood after co- 
agulation. 
As fibrin may be seen to arise in the form of threads, under 
the microscope, in coagulating blood, and since no trace of it in 
any form has been detected in the plasma, and the process can 
_be accounted for otherwise, it seems unjustifiable to assume 
that fibrin exists preformed in the blood, or arises in any way 
prior to actual coagulation. 
Fibrin belongs to the class of bodies known as proteids, and 
can be distinguished from the other subdivisions of this group 
of substances by certain chemical as well as physical charac- 
teristics. It is insoluble in water and in solutions of sodium 
chloride; insoluble in hydrochloric acid, though it swells in 
this menstruum. 
It may be whipped out from the freshly shed blood by a 
bundle of twigs, wires, or other similar arrangement present- 
ing a considerable extent of surface; and when washed free 
from red blood-cells presents itself as a white, stringy, tough 
substance, admirably adapted to retain anything entangled in 
its meshes. If fibrin does not exist in the plasma, or does not 
arise directly as such in the clot, it must have some antecedents 
already existing as its immediate factors in the plasma, either 
before or after it is shed. 
We shall here present certain facts, and examine the conclu- 
sions drawn from them afterward : 
1. Blood may be prevented from coagulating & receiving it 
in a solution of a neutral salt (magnesium sulphate, etc.), and 
upon certain chemical treatment precipitate a body which may 
be obtained by additional manipulation as a white, flaky sub- 
stance, that may be shown not to be fibrin, but which will 
clot and so give rise to this body. Such is the plasmine of 
Denis. 
2. By treatment of plasma with solid sodium chloride, two 
bodies with different coagulating points, but belonging to the 
same group of proteids (globulins, soluble in saline solutions), 
may be obtained, denominated paraglobulin and fibrinogen re- 
spectively. 
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