The vessels injured in incised wounds are either arteries or veins, and each require attention from the surgeon, as the bleeding from them requires somewhat different treatment. When an artery is wounded, there is an immediate retraction of the ends of its middle and iuterual coats within the outer or investing coat, and also a contraction of all the coats so as to diminish the calibre of the artery. Blood flows from both ends of a divided artery, but always in greater quantity from the orifice nearest the heart. The blood from an artery can easily be dis tinguished by its bright red colour and by its coming out in jerks.
When a cut artery is left to itself, the effusion of blood is great, but the flow becomes less and less profuse, and in passing over the rough ened surface of the external sheath, from which the two inner coats have been separated by retraction, particles of the blood adhere to its loosened filaments. These particles keep increasing in number, till at last the whole space between the end of the external sheath and the ends of the two retracted coats is filled up, the blood having formed there a firm coagulated mass. When this process is completed, the bleeding from the artery stops. This mass of coagulated blood is called the external coagalum, but the same process is carried on within the retracted inner coats of the divided artery, and the coagulum is continued up to the point at which the artery gives off one of its branches. This coagulum terminates with a conical extremity in the middle of the tube of the artery, and is called the internal coagulum.
The blood also which is effused outside the artery altogether coagulates, and to eorno extent may assist in the natural process of arresting the haemorrhage. But these coagula of blood would not be sufficient alone to restrain the limmorrhage ; another process follows, which perma nently effects this. This consists in the effusion of lymph from the parietes of the artery itself. This lymph fills up the entire extremity of the artery, and ie first deposited between the external and internal coagula, but it goes on increasing till at last it occupies their position, the coagula are absorbed, and the lymph, becoming eventually organised by the development within its substance of blood-vessels, forms a part, as it were, of the artery itself, and connects it more or less with the surrounding parts.
When an artery is only partially divided or punctured, a somewhat. different process takes place. Blood is effused between the artery and its sheath, both above and below the wounded part. In consequence of this the artery is distended, and a difference in the relative positions of the internal coats and the sheath takes place, and the blood coagu lating is confined by the sheath over the wounded part of the internal coats. Lymph is effused as in the former case, and the cure is only
effected by the obliteration of the artery.
When the veins are wounded, the blood which is poured out is of a dark colour, and comes not by jerks, but in a uniform stream. There is not so much danger from the bleeding of a vein as an artery, and it is much more easily stopped. When a vein is cut through, the oppo. site ends are closed by blood and the subsequent orgauisatien of lymph, as in arteries. If only slightly punctured. and longitudinally, veins quickly heal, as is seen iu the common operation of venest•ctien. When veins are wounded obliquely or transversely, the wound is closed by a coagulum of blood, add the lips of the wound secrete lymph, which eventually becomes organised, and blocks up the whole vein. Eventu ally the coagulum thus formed is absorbed. This reparative process is much longer in taking place than that which occurs In arteries under the same circumstances.
7'reeireent.—In the treatment of incised wounds the objects in view are, first, to arrest the haemorrhage ; secondly, to remove all foreign bodies that may have been introduced into the wound ; and, thirdly, to promote the union of the divided parts.
The arrest of bleediug is easily accomplished by bringing the edges of the wound together, in superficial wounds, and wounds where nu large arterial or venous trunks have been injured ; but where large vessels have been injured, other means will be found necessary. There is nothing perhaps which distinguishes modern surgery more than the power which it has attained of arresting hannorrhage. The surgeon, through his knowledge of the circulation and the means of arresting mechanically the flow of blood, can venture upon cutting through all but the principal trunks of the arterial and venous system. When the bleeding from a wound is great, the first thing that can be done to arrest it is to compress the trunk of the artery which supplies the part. This may be done by means of the tourniquet [Tounsesurr], or a bandage so constructed as to press down upou the artery. The circu lation of the blood in the arterial trunk being arrested, the hremordiuge from the wound will in a great measure cease. Compression however can seldom be used for a sufficient length of time to act as a curative agent in stopping the flow of blood. In the first place, although pressure by bandage may stop the supply of blood through the principal arterial trunk, it will not stop it through deeper-seated branches; amid, by arresting the return of the blood by the veins, it may, under certain circumstances, tend to iucreaso the bleeding. Even when eircuin stances are most favourable, the tourniquet and bandages are likely to get displaced, and thus to suffer the return of the bleeding.