The principles of surgery . After a longer time,vessels begin to pass even into the clotwhen this is present; these vessels beingalways in connection with those of thesheath and external lymph, and not pro-ceeding, as has been supposed, from the in-terior of the artery1 (Figs. 184, 187). The portion of the external coat inclu-ded in the noose of the ligature is neces-sarily killed, by mechanical injury; andbeing dead, it must be separated. Detach-ment is effected in the ordinary way; byinflammation and ulceration. These de-structive processes extend no further oneither side of the ligature, th
The principles of surgery . After a longer time,vessels begin to pass even into the clotwhen this is present; these vessels beingalways in connection with those of thesheath and external lymph, and not pro-ceeding, as has been supposed, from the in-terior of the artery1 (Figs. 184, 187). The portion of the external coat inclu-ded in the noose of the ligature is neces-sarily killed, by mechanical injury; andbeing dead, it must be separated. Detach-ment is effected in the ordinary way; byinflammation and ulceration. These de-structive processes extend no further oneither side of the ligature, than what issufficient for detachment of the foreign body,with the dead portion of arterial no accident by bleeding occurs; for two reasons ;—First^on accountof the limited extent of ulceration; second, because the arterial tube hasbeen, at that part, and some way beyond it, completely consolidated. The first part of Mr. Spences researches may be found in the Monthly Journal, May,1843. The second is Fig. 187. Carotid of a dog ; 12th dayafter deligation. Vascularization ofthe clot, by vessels from without. Ata. the artery cut open, showing- theclot; at b, the external vessels, coursingonwards, enter the clot at c. Fig-. circulation shown in thethigh. At a, the femoral artery hasbeen obliterated by ligature. 502 COLLATERAL CIRCULATION. Thus the ligature, and the dead portion of areolar coat embraced byits noose, are detached from the living texture. There may be a Blightobstacle to extrusion, from the external fibrinous deposit—threateningto confine, as the substitute bone often does the sequestrum; but a Blighttouch of the free end of the ligature suffices to counteract this. On theligatures final extrusion, the hiatus, so occasioned, is quickly filled upby fresh exudation ; and all is consolidated. A dense compact swelling,of some size, thus comes to oceupy the place of the arterial tube, at thedeligated point. Such copious exudation an
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