32 <;kneral phenomena of coagulation. 



little tendency to coagulate when alkaline mucus from the vagina is mixed with it. 

 If it be rapidly discharged, it coagulates in masses. Foetal blood at the moment of 

 birth coagulates soon. 



(/) Blood rich in fibrin from inflamed parts coagulates slowly, but the clot so 

 formed is firm. 



(g) [Blood coagulates more slowly in a smooth than a rough vessel, and also in 

 a shallow vessel than in a deep one.] 



Haemophilia. A very slight scratch in some persons may cause very free bleeding. These 

 persons are called colloquially "bleeders," and are said to have haemophilia or the hemorrhagic 

 diathesis. In " bleeders " coagulation seems not to take place, owing to a want of the 

 substances producing fibrin ; hence, in these cases, wounds of vessels are not plugged with 

 fibrin. [A tendency to hiemorrhage occurs in scurvy, purpura, in some infectious diseases, 

 such as typhus, plague, yellow fever, and in poisoning with phosphorus.] 



Injection of Peptones. Albertoni observed that if tryptic pancreas ferment (dissolved in 

 glycerine) be injected into, the blood of an animal, the blood does not coagulate. Schmidt- 

 Mulheim found that after the injection of pure peptone into the blood (0*5 gram per kilo.) of a 

 dog, the blood lost its power of coagulating. [This occurs in the dog, but not in the rabbit. 

 Pentonised blood coagulates when it is treated with C0 2 or water. It appears, however, that 

 it is not the ]>eptone which prevents the coagulation, but the albumoses adhering to it which 

 do so.] A substance is formed in the plasma, which prevents coagulation, but which is pre- 

 cipitated by C0 L Lymph behaves similarly (Fano). After peptones are injected, there is a 

 great solution of leucocytes in the blood (v. Samson- Himmelstjema). The secretion of the 

 mouth of the medicinal leech, [although its action is not due to a ferment (Haycraft)], and 

 y snake poison also prevent coagulation ( Wall). [Diastatic ferment also prevents coagulation 

 (Salvia! i).] 



III. Coagulation is accelerated (a) By contact with foreign Substances 

 of all kinds, but only when the blood adheres to them, hence, threads or needles 

 introduced into arteries are rapidly covered with fibrin. Blood does not coagulate 

 in contact with bodies covered with fat or vaseline (Frtund). Even the introduction 

 of air-bubbles into the circulation or the passage of indifferent gases, N or H, 

 through blood, accelerates it. The pathologically altered wall of a vessel acts like 

 a foreign body. Blood shed from an artery rapidly coagulates on the walls of 

 vessels, on the surfaces exposed freely to air, and on the rods or twigs used to beat it. 



(b) The products of the retrogressive metabolism of proteids (uric acid, glycin, 

 leucin, taurin, kreatin, sarkiu, but not urea) favour coagulation by increased 

 ferment formation ; but if they are added in excess, they retard the process. 



From a watery extract of the testis or thymus, on the addition of acetic acid, is precipitated a 

 substance which is soluble in sodic carbonate. It is a mixture of lecithin and albumin, and 

 when it is injected into the blood-stream it causes almost instantaneous death by intravascular 

 coagulation ( Wooldridge). 



(c) During rapid hemorrhage, the last portions of blood coagulate most rapidly 

 (Ilohmann). 



(d) Heating the blood from 39 to 55 C. (Heivson). 



(e) Agitation of the blood (II T ewsi >n and Hunter). 

 [(f) The addition of a small quantity of water. 



({/) A watery condition of the blood. The clot is small and soft. 

 (/*) Contact with oxygen. J 



IV. Rapidity of Coagulation. Amongst vertebrates, the blood of birds 

 (especially of the pigeon) coagulates almost momentarily ; in cold-blooded animals 

 coagulation occurs much more slowly, while mammals stand midway between the 

 two. 



IThe blood of a fowl begins to coagulate in $ to 1 minute ; pig, sheep, rabbit, in } to 1} 

 minute ; dog, 1 to 3 minutes ; horse aud ox, 5 to 13 minutes ; man, 3 to 4 minutes ; solidifica- 

 tion is completed in 9 to 11 minutes (Nassc).] The blood of invertebrates, which is usually 

 colourless when it is oxidised ( 32), forms a soft whitish clot of fibrin. Even in lymph and 

 chyle, a small soft clot is formed. 



V. When coagulation occurs, the aggregate condition of the fibrin -factors is 

 altered, so that heat must be set free ( Valentin, 1844). 



