UNION. 



are taken notice of by the earliefl: writers upon phyfic and 

 furgery ; and diftinguifhed from one another by different 

 appellations or terms of art. Union by the firft intention 

 was the terra which Galen employed to exprefs that mode 

 of healing Grounds, in which the union is fpeedily produced 

 merely by keeping their edges in contaft : an operation of 

 nature, now frequently denominated healing by the procefs 

 of adhefion ; while union by the fecond intention was a term 

 employed by the fame phyfician to indicate the feries of 

 phenomena which occur in that flower mode of heahng 

 wounds, in which their edges coalefce more flowly ; pheno- 

 mena to which modern furgeons now ufually give the name 

 of heahng by the procefs of granulation. See Leftures on 

 Inflammation, p. 206, 207. 



We have alfo examples of an union, very fimilar to that 

 by the firft intention, in bones which have been fraftured ; 

 in tendons which have been ruptured ; and even fometimes in 

 mufcles which have been wholly or partially torn afunder, 

 without any divifion having been produced in the Ikin which 

 covers fuch parts. In the fudden and violent divifion of 

 thefe textures, a greater or lefs quantity of blood is always 

 effufed into the line of feparation between the divided parts, 

 and a quantity of that fluid is at the fame time poured out 

 alfo into the cellular membrane contiguous to or immedi- 

 ately furrounding the folution of continuity. When the 

 blood which is effufed is not very conliderable in quantity, 

 and when the parts from which it has been effufed have not 

 been too feverely injured, it is obferved to be gradually ab- 

 forbed ; and in proportion as the effufed blood is abforbed, 

 the divided parts feem to approach nearer together. If the 

 divided furfaces be examined a few hours after the divifion, 

 or folution of continuity, has been produced, they will be 

 found to be covered with a fubftance, which, in its appear- 

 ance and other properties, refembles very exaAly the coagu- 

 lable lymph, or, as it is now often termed, the fibrin of the 

 blood. 



This coagulable lymph appears to be effufed very foon 

 after the injury. Profeffor Thomfon found, that in animals, 

 a diftinft layer of it was effufed over their wounds in lefs than 

 four hours. (P. 209. ) But, fays he, whatever may be the 

 period at which it is firft formed, it is now well afcertained, 

 that in healthy fubjefts, when fraftured, torn, or ruptured 

 furfaces, to which the external air has not been admitted, 

 are properly covered with this layer of coagulable lymph, 

 and come into contacft, they fpeedily coalefce, and that, by 

 this lymph becoming a living intermedium, the continuity 

 of the divided part is at length reftored. 



Appearances, precifely fimilar to thofe occurring in divi- 

 fions without communication with the external air, take 

 place in fimple incifed wounds, the edges of which have 

 been brought together before, or foon after the bleeding 

 from the divided veffels has ceafed. If a wound of this 

 kind be torn open foon after its reunion, the furfaces which 

 had been united are feen covered with a fubftance refembhng 

 an animal jelly. This is the coagulable lymph or fibrin of 

 the blood. It has been fuppofed, that the lymph is poured 

 out from the fmaller veflels which are divided ; but profeffor 

 Thomfon thinks it more probable that it is chiefly, if not 

 wholly, formed by the fecreting aftion of the capillary veffels 

 of divided furfaces. 



The coagulable lymph, foon after its exudation, becomes 

 penetrated with blood-veffels, which proceed from the divided 

 furfaces, appear to join in the procefs of reunion by open 

 extremities, or, in other words, to inofculate with one an- 

 other. The blood now circulates freely through the newly 

 formed channels of communication eftablifhed between the 

 veffels which penetrate the lymph efifufed upon the furfaces 



formerly divided. This is the ftate or ftage of reunion, 

 which Mr. Hunter has denominated the adhefive inflamma- 

 tion. The veffels which (hoot into the coagulable lymph 

 often acquire, in the courfe of a few hours, a fize rendering 

 them capable of being injeifted. 



The precife manner in which the veffels are extended into 

 the coagulable lymph is ftill unknown. It has not been po- 

 fitively fettled, whether it is the divided veflTels which pene- 

 trate the lymph. The extremities of the larger branches, 

 are clofed with the effufed lymph, and removed by means of 

 it, and their natural elafticity, to a diftance from each other. 

 Dr. Thomfon conceives, that thefe circumftances are infur- 

 mountable bars to their immediate inofculation ; and he ob- 

 ferves, that if it be the clofed veffels which are prolonged 

 into the lymph, each fmall artery, it is obvious, muft have 

 its correfponding vein. And though the veffels from the 

 oppofite divided furfaces may by prolongation pafs each other 

 in a wound, it is not eafy to conceive the manner in which 

 they will join, or inofculate, nor how the artery becomes 

 afterwards connefted with the vein. But the inofculation, 

 or direct union of the fmall blood-veffels, from the oppofite 

 furfaces of wounds, however difficult to conceive or explain, 

 is a truth undeniably eftabliflied. Thomfon, p. 212. 



Duhamel made an experiment, which fully proves, that in 

 the reunion of parts which have been divided, the blood- 

 veffels from the oppofite furfaces inofculate direftly, and do 

 not merely pafs one another. He broke the legs of fix 

 chickens, and after the bones had reunited, he cut through 

 about one-third of the foft parts, covering the callus, or 

 new bone. When the wound had healed up, he divided an- 

 other third part, and, in the fame manner, the remaining 

 third part, fparing neither blood-veffel, tendon, nor nerve. 

 Only one of the fix chickens furvived thefe cruel operations ; 

 but upon injefting the artery at the upper part of the thigh, 

 the injeftion was found to have penetrated to the loweft part 

 of the leg. " I cannot fay (Duhamel remarks) whether 

 the large veffels, filled bv the injeftion, were dilated capillary 

 veffels, or the large veffel of the leg itfelf, which had been 

 reunited ; but the experiment proves irrqfragably the inofcu- 

 lation of the blood-veffels." Later obfervations than thofe 

 of Duhamel (fays profeffor Thomfon) have (hewn that it is 

 by the fmall veffels, and not by the larger trunks, that the in- 

 ofculations are formed by which the divided parts in a limb 

 are fupplied with blood. 



Mr. Hunter conceived that he had certainly fuccecded in 

 obferving inofculation on the tunica conjunftiva of the eye, 

 the veffels of which are frequently divided by furgeons in 

 cafes of ophthalmy. He ftates, that the two ends of the 

 cut veffel are feen to (brink ; but, after a little while, they 

 are perceived to unite, and the circulation is carried on as 

 before. (Hunter on the Blood, &c. p. 193.) Dr. Thom- 

 fon's experiments and obfervations lead him, however, to be- 

 lieve, that it is not the divided extremities of the arteries 

 that again unite, but the folds of fmall branches, that are 

 prolonged into the intermediate fpace, which become the 

 channels of communication between the larger trunks that 

 had been divided, but the extremities of which had been 

 previoufly clofed. 



Mr. Hunter was of opinion that blood fometimes ferved 

 as a medium of reunion, or vital bond of conneftion between 

 parts which have been divided, and that blood-veffels formed 

 and inofculatcd with each other in this eff"ufed or extrava- 

 fated blood. The praftical furgeon, however, finds the inter- 

 pofition of this fluid between the furfaces of a wound difad- 

 vantageous, and if any material quantity be fo fituated, it 

 always becomes a certain impediment to union by the firft 

 intention. There are, it is true, fome inftances in which 

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