66 FIBRIN. 



the blood has been received. By solution with water of the blood- 

 corpuscles in the broken-up blood-clot the fibrin can be isolated. 



If the blood-corpuscles sink rapidly in the blood, and if the advent 

 of coagulation be delayed, the upper layer of the blood-clot is only 

 stained yellow on account of the absence of enclosed erythrocytes. 

 This is the rule with horses' blood, but it has been observed in the case 

 of human blood, particularly when inflammation was present in some 

 part of the body. Therefore, this layer has also been designated crusta 

 phlogistica. Such blood is richer in fibrin and therefore coagulates more 

 slowly. 



The crusta forms also under other conditions, but the cause of its formation 

 is not always clear. Thus it occurs when the specific gravity of the blood-cor- 

 puscles is increased or that of the plasma is diminished, as in cases of hydremia 

 and chlorosis, in consequence of which the corpuscles sink more rapidly, and 

 during pregnancy. The taller and narrower the vessel, the higher is the crusta. 



It can be readily understood why the blood-clot undergoes greater contraction 

 and appears more contracted in the neighborhood of the unpigmented layer free 

 from corpuscles. 



If freshly shed blood is whipped with a rod the filaments of fibrin 

 that form collect about the rod, and in this way the fibrin is obtained 

 as a fibrous, grayish-yellow mass from the blood now become defi- 

 brinated. 



The plasma exhibits analogous phenomena, but it forms only a soft, 

 tremulous jelly, by reason of absence of the resistant blood-corpuscles. 

 The plasma undergoes coagulation only when it contains leukocytes. 

 If these be removed by filtration the plasma is no longer coagulable. 



Although the fibrin appears voluminous, it constitutes only from 

 o.i to 0.3 per cent, of the mass of the blood. In this connection, it is 

 noteworthy that in two different specimens of the same blood the 

 amount of fibrin may vary considerably. 



Fibrin is insoluble in water or ether. Alcohol causes it to shrink by 

 dehydration, while hydrochloric acid causes it to swell and assume a 

 vitreous appearance, with transformation into syntonin. In the fresh 

 state fibrin is tough and elastic. If dried, it becomes horn-like, trans- 

 lucent, brittle, and pulverizable. 



Fresh fibrin is capable of actively decomposing hydrogen dioxid into water 

 and oxygen, just as other fresh animal or vegetable tissue is likewise capable of 

 doing. Boiled or preserved in alcohol it loses this power. In the fresh state 

 it is soluble in from 6 to 8 per cent, solutions of sodium nitrate or sodium 

 sulphate, with the formation of globulin; and in dilute alkalies and ammonia, 

 with the formation of alkali-albuminate. These solutions are not coagu- 

 lated by heat. Also weak solutions of haloid salts (sodium chlorid, ammonium 

 chlorid, potassium iodid, sodium iodid, sodium fluorid, ammonium fluorid) dis- 

 solve fibrin at a temperature of 40, as, for instance, sodium-chlorid solution, from 

 7 to 20 parts in the thousand, with the production of globulin-bodies and pro- 

 peptone. Fibrin from swine is dissolved by 0.5 per cent, hydrochloric acid 

 and also by malic, oxalic, butyric, acetic, citric, and lactic acids; fibrin from 

 cattle, with greater difficulty. Fibrin exposed to air for a considerable time is not 

 soluble in nitric acid, although it is soluble in neurin. As a result of putrefaction 

 it likewise undergoes solution, with the formation of albumin. Fibrin contains 

 lime, iron, and magnesium. 



According to Schmiedeberg the fibrin obtained from plasma has the 

 elementary formula C 108 H 162 N 30 SO 34 , while blood-fibrin has the following 

 composition: C 112 H 16 gN 30 SO 35 -f- ^H 2 O. 



