THE BLOOD. 207 



does not coagulate). Blood received into a vessel filled with oil does 

 not coagulate. Coagulation is prevented when the blood is in con- 

 tact with normal, living, vascular walls. The addition of certain 

 articles retards coagulation ; thus, feeble doses of alkalies, carbonate 

 of sodium and potassium, sugar, water and albumin. In lightning 

 strokes, the blood does not coagulate. 



Agents Accelerating Coagulation. I have alluded to the action 

 of calcium salts in the different acts of coagulation. 



1. The internal use of calcium chloride or calcium lactate 

 shortens the time of coagulation. Gelatin also accelerates coagula- 

 tion, which has been ascribed by Grley to the lime salts in the gelatin. 

 2. A temperature a little higher than that of the body (102 to 107 

 F.). 3. Presence of foreign bodies. If a needle be made to pene- 

 trate the wall of a vessel, fibrin is deposited upon it and so produces 

 coagulation. It seems to be a sort of phenomenon analogous to that 

 which occurs when a thread is suspended in a solution of sugar, when 

 the crystals of sugar are deposited upon it. Injections of laky blood 

 accelerate coagulation. 



The Acceleration of Coagulation by Tissue Substances. It has 

 been known for a long time that not only in the blood-serum, but 

 also in the different cellular elements of the organism, there was a 

 substance which accelerated coagulation. It was known by the name 

 of cell-globulin, cell-fibrinogen, nucleo-proteid of tissue, etc. Pekel- 

 haring showed that this body in the tissues acted like fibrin-ferment. 

 According to Schmidt, this body is a zymoplastic substance. Its 

 nature is at present unknown. 



Fuld and Spiro from experiments upon the action of tissue 

 extract upon the plasma of the goose conclude that the acceleration 

 of coagulation increases with the square root of the quantity of 

 extract, which corresponds to the Schiitz-Bbrrisow law for ferments, 

 and makes the action of thrombin like a ferment. 



Pathological Action. If the wall of a blood-vessel becomes dis- 

 eased, as in atheroma, it loses the power to prevent clotting, and a 

 clot may form. 



Why Blood does not Normally Coagulate within the Blood- 

 vessels. Much time and experiment have been given to ascertaining 

 the cause for noncoagulation within living walls, but notwithstanding 

 the question is yet unsettled. By some it is thought that the 

 destruction of the white corpuscles is not extensive enough to fur- 

 nish the proper supply of nucleo-proteid, from which fibrin-ferment 

 is manufactured. According to Schmidt, the blood within the living 



