ITS VITAL PROPERTIES, AND RELATIONS TO LIVING ORGANISM. 195 



than those first obtained. In blood drawn during Inflammatory states, again, 

 the coagulation is usually slow, but the clot is preternaturally firm ; especially 

 at its upper part, where the Buffy coat ( 189) or colorless stratum of fibrin, 

 gradually contracts, and produces the cup, which may be generally considered 

 to indicate a high degree of Inflammation. Although the Blood withdrawn 

 from the body coagulates (except under the peculiar circumstances just stated) 

 whether it be kept at rest or in motion, whether its temperature be high or low, 

 and whether it be excluded from the air, or be admitted to free contact with the 

 atmosphere, yet its coagulation may be accelerated or retarded by variation in 

 these conditions. If the blood be continually agitated in a bottle, its coagula- 

 tion is delayed, though it will at last take place in shreds or insulated portions; 

 but that rest is not the cause of its coagulation (as some have supposed) is 

 proved by the fact that, if a portion of blood be included between two ligatures 

 in a living vessel, it will remain fluid for a considerable time ;* as it also will 

 when effused into the midst of living tissues, or kept in a state of stagnation 

 in parts affected with inflammation. Thus Mr. Gulliver, besides other instances, 

 mentions a remarkable case witnessed by himself, in which a collection of blood 

 which had been effused in consequence of a bruise on the loins, was found un- 

 coagulated when let out twenty-eight days afterwards; it measured five ounces, 

 was as liquid as blood just drawn from a vein, and showed the normal characters 

 when examined microscopically; and it coagulated in a cup in less than thirty 

 minutes (op. cit., p. 17). And Mr. Paget mentions that he has known the 

 blood remain fluid in the vessels of an inflamed part, though in a state of com- 

 plete stagnation, for as long as three days. 2 Again, the coagulation is accelerated 

 by moderate warmth, the natural heat of the body from which the blood is taken 

 appearing to be most favorable to it; but the coagulating power appears to be 

 destroyed by a temperature of about 150, blood heated to that point remaining 

 permanently fluid. (Gulliver, op. cit., pp. 4, 5.) On the other hand, the co- 

 agulation is retarded by cold ; but the coagulating power is not destroyed even 

 by extreme cold ; for if blood be frozen immediately that it is drawn, it will 

 coagulate on being thawed. Moreover, it is accelerated by exposure to air, but 

 it is not prevented by complete exclusion from it, as is proved by its taking 

 place in a vacuum, or in a shut sac within the dead body : complete exclusion 

 from the air, however, retards the change ; as has been shown by causing blood 

 to flow into a vessel containing oil, which will form an impervious coating on its 

 surface, and will occasion the coagulation to take place so slowly, that the red 

 particles have time to subside, and the upper stratum of the clot is colorless. 3 

 The effect of the addition of strong solutions of neutral salts to fresh blood, is 

 usually to retard, and sometimes even to prevent, its coagulation ; and the same 

 effect is produced by many vegetable substances, particularly those of the nar- 

 cotic and sedative class, such as opium, belladonna, aconite, hyoscyamus, digi- 

 talis, and tea or coffee in strong infusion. 4 The action of most of the sub- 

 stances, however, which preserve the fluidity of the blood, only continues during 



1 The testimony of all experimenters is in accordance on this point, although they differ 

 as to the length of time that elapses before coagulation commences. Mr. Gulliver states 

 that out of many trials made by him, the coagulation commenced within two hours in only 

 a few instances ; more commonly, three, four, or five hours elapsed before any clot was 

 formed ; and in one instance the coagulation was incomplete at the end of twenty-four 

 hours. In all these experiments, the blood coagulated in the course of a few minutes, when 

 withdrawn from the living vessel. See Mr. Gulliver's edition of " Hewson's Works," p. 23. 



2 "Lectures on Inflammation," in "Medical Gazette," 1850, vol. xlv. p. 971. 



3 Dr. Babington in " Medico-Chirurgical Transactions," vol. xvi. 



4 See Dr. J. Davy's "Anatomical and Physiological Researches," vol. ii. pp. 101, 102; 

 and Mr. Prater's "Experimental Inquiries in Chemical Physiology," pp. 59, 63, &c. A 

 copious table of the results of their experiments is given in Mr. Ancell's "Lectures on the 

 Physiology and Pathology of the Blood," in the "Lancet" for Dec. 21, 1839. 



