532 OF ABSORPTION AND SANGUIFICATION. 



A complete demonstration of the truth of the Hunterian doctrine, that the 

 Blood might become organized, like plastic exudations of " coagulable lymph," 

 has been lately afforded by the researches of Dr. Zvvicky, on the changes 

 occurring in the clots of blood which form in blood-vessels, above the points 

 where they have been tied. He has traced the successive stages of the meta- 

 morphosis of the coagulum into fibre-cellular tissue, and the formation of ves- 

 sels in its substance ; the whole process taking place exactly as in an inflam- 

 matory exudation, and the blood-corpuscles exerting no other influence upon 

 it, than that of slightly retarding it. 



701. When the Blood is withdrawn from the body, however, its Coagula- 

 tion is the last act of its life ; for, if not within the influence of a living sur- 

 face, it soon passes into decomposition. Instances occasionally present 

 themselves, in which the Blood does not coagulate after death ; and in most 

 of these, there has been some sudden and violent shock to the Nervous sys- 

 tem, which has destroyed the vitality of solids and fluids alike. This is 

 generally the case in men and animals killed by lightning, or by strong elec- 

 tric shocks ; and in those poisoned by prussic acid, or whose life has been 

 destroyed by a blow on the epigastrium. It has also been observed in some 

 instances of rupture of the heart, or of a large aneurism near it; and a very 

 interesting phenomenon then not unfrequently presents itself, the coagulation 

 of the Blood which has been effused into the pericardium (the effusion having 

 taken place during the last moments of life), whilst that in the vessels has re- 

 mained fluid. In several of the instances in which the blood has been found 

 uncoagulated in the vessels, many hours after death, a portion withdrawn from 

 the body has clotted; and Dr. Polli asserts that the complete absence of 

 coagulability is a phenomenon which has no real occurrence. During a long 

 course of researches on this subject, he has never yet met with an instance, 

 in which the blood, when left to itself, and duly protected from external 

 destructive influences, did not coagulate before becoming putrid, lie has 

 even more than once caused blood to coagulate, which had been taken in a 

 fluid state from the veins, thirty-six or forty-eight hours after death.* It ap- 

 pears that simple arrestment of Nervous influence favours the coagulation of 

 the blood in the vessels ; clots being found in their trunks, within a few 

 minutes after the Brain and Spinal marrow have been broken down. 



702. The length of time which elapses before Coagulation, and the degree 

 in which the clot solidifies, vary considerably ; in general, they are in the 

 inverse proportion to each other. Thus, if a large quantity of blood be with- 

 drawn from the vessels of an animal at the same time, or within short inter- 

 vals, the portions that last flow coagulate much more rapidly, but much less 

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

 again, the coagulation is usually slow, but the clot is preternaturally firm ; espe- 

 cially at its upper part, where the Buffy coat ( 704) or colourless stratum 

 of Fibrine, gradually contracts, and produces the cup, which is usually re- 

 garded as indicative of a high degree of Inflammation. Except under the 

 peculiar circumstances just stated, the Blood withdrawn from the body always 

 coagulates;! 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. The Coagulation may be accelerated or 

 retarded, however, by variation in these conditions. Thus, if the blood be 

 continually agitated in a bottle, its coagulation is delayed, though it will at last 



* Rankings Half-Yearly Abstract, vol. ii. p. 337. 



f 01 lie diseases may ]>rrli;i[).< \><- an exception ; non-coagulation of the Blood is said to be 

 characteristic of the Scurvy, but this is erroneous. In very severe forms of Typhus, the sumo 

 lias been stated to occur. 



