42 PHENOMENA OF COAGULATION. 



precipitated by C0 2 . Lymph behaves similarly (Fano). After peptones are injected, 

 there is a great solution of leucocytes in the blood (v. Samson-Himmelstjerna). 



III. Coagulation is Accelerated (a.) By Contact with Foreign 

 Substances of all kinds ; hence, threads or needles introduced into 

 arteries are rapidly covered with fibrin. Even the introduction of 

 air-bubbles into the circulation accelerates it, and the pathologically 

 altered wall of a vessel acts like a foreign body. Blood shed from 

 an artery rapidly coagulates on the Avails of vessels, on the surfaces 

 exposed freely to air, and on the rods or twigs by which it is beat. 

 The passage through it of indifferent gases, such as N. and H., and 

 the addition of H 2 have the same effect. 



(b.) Heating from 39 to 55C., rapidly facilitates coagulation 

 (Hewson). 



(c.) Agitation of the blood, as shown by Hewson and Hunter. 



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. [The blood of a fowl begins 

 to coagulate in a-half to one and a-half minute ; that of a pig, sheep, 

 rabbit, in a-half to one and a-half minute ; of a dog, one to three 

 minutes ; of a horse and ox, five to thirteen minutes ; of man, three 

 to four minutes ; solidification is completed in nine to eleven minutes, 

 but rather sooner in the case of women (Nasse) ]. The blood of 

 invertebrates, which is usually colourless, 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, 1884, Schiffer, 

 Lepine). The rise in the temperature may be ascertained with a very 

 delicate thermometer. 



VI. In blood shed from an artery, the degree of alkalinity diminishes 

 from the time of its being shed until coagulation is completed (Pfliiger 

 and Zuntz). This is probably due to a decomposition in the blood, 

 whereby an acid is developed, which diminishes the alkalinity (p. 2). 



VII- Whether or not electricity is developed, is not positively proved. Hermann 

 supposes that the parts already coagulated are negative, while non-coagulated 

 parts are positive ; but this has not been clearly shown. 



VIII. During coagulation there is a diminution of the in the blood, 

 although a similar decrease also occurs in non-coagulated blood. Traces 

 of ammonia are also given oft', which Eichardson erroneously supposed 

 to be the cause of the coagulation of the blood. [This is refuted (1.) 

 by the fact that blood, when collected under mercury (whereby no 

 escape of ammonia is possible), also coagulates ; and (2.) by the follow- 



