A system of surgery . ll as by the effect of the direct impact of the blood-streamupon that part of the sac opposite its mouth. But if a clot adheresto part of the sac and becomes organised, it strengthens the sac atthis spot, and the chief growth then takes place where the sacis thinner and weaker. The contents of every uncured sacculated aneurysm consist inpart at least of ordinary arterial blood, which after death appearsas a soft black blood-clot. In nearly all cases, more or less clottingof the blood occurs during life, and these clots play a most importantpart in the history of an aneury
A system of surgery . ll as by the effect of the direct impact of the blood-streamupon that part of the sac opposite its mouth. But if a clot adheresto part of the sac and becomes organised, it strengthens the sac atthis spot, and the chief growth then takes place where the sacis thinner and weaker. The contents of every uncured sacculated aneurysm consist inpart at least of ordinary arterial blood, which after death appearsas a soft black blood-clot. In nearly all cases, more or less clottingof the blood occurs during life, and these clots play a most importantpart in the history of an aneurysm. The clots vary greatly inamount, in arrangement and in appearance. They are usuallyfound in concentric layers pressed firmly against the sac, many ofthe layers being firm and almost colourless, others being softer andmore granular, and coloured with varying shades of red and coagulation results from the adhesion of the ferment-containingcorpuscles to the interior of the sac, and their subsequent disinte-. Fig. 171.—Sacculated Aneurysm of Com-mon Carotid Artery. o, Common carotid artery; 6, ext. carotidartery ; c. int. carotid artery ; d. sac of aneu-rysm ; e, laminated clot partly filling sac. SACCULATED ANEURYSM. 597 gration, which sets free the ferment and leads to the formation offibrin. The differences in the clots is explained in two ways : one viewis that if this fibrin forms in a rapid blood-stream, the corpuscles are,as it were, whipped out of it, and a clot of nearly pure fibrin isthe result; such a clot is called a tvhite clot, from its colour, andan active clot, from its supposed special active share in thecure of aneurysm, and a laminated clot from its occurrence in severalimbricated layers (Fig. 171). If, however, the fibrin separates inblood that is nearly or quite stagnant the corpuscles are caught in itsmeshes, and a red, passive, or blood clot results. Between these twoextremes, of a rapid blood-stream and stasis, all gradations occur,and theref
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