But the plastic product is not always in the form of a plug, moulded to the cavity of the vein : it sometimes consists of shreds or fringes of lymph, firmly attached to the lining of the vein, and hanging into its cavity, either from the walls or in festoons from the valves.* The walls of the vein, at the same time, undergo change, indicative of the same inflam matory phenomena, which consists mainly in interstitial plastic deposit among the areolar tissue of the tunics.
" So soon as a fibrinous plug of this de scription is established, the red and violet speckled colouring abates in intensity, and the internal membrane, losing its smoothness and polish, assumes a dull velvety or slightly puckered appearance. The external mem brane appears thickened, turgid, and soon becomes adherent to the cellular tissue, which in its turn has been rendered firmer and paler from the effusion of plastic lymph. Both membranes are still readily distinguishable, and even separable, from each other ; the con sistency of their texture is however impaired, and they are easily torn. In this state of things a vein, when cut asunder, does not col lapse, even after the plug has been removed ; but, on the contrary, its calibre remains open like that of an artery. This is more than ever the case when the surrounding cellular tex ture has acquired firmness by the condensa tion of the inflammatory product infused into it, or when it puts on a brawn-like character, and intimately coalesces with the external membrane of the vessel.t These phxnomena may occur in veins of any size ; and to any extent in an3 ;rarticular set of vessels. They occasion obstruction of the circulation in all vessels tributary to the one affected. Of such a condition Phlegmasia alba dolens may be instanced as an example.
As regards the cause of plastic phlebitis, or, indeed, of venous inflammation in general, it may be the result either of spontaneous action, or the circulation of poisoned blood— the latter being infinitely the most common cause. In the latter case the inflammation of the vein is excited by contact of a coagu lum of vitiated blood with the lining of the vessel. But the veins may, as well as other tissues and organs, be the seat of spontaneous inflammation. This is frequent in some forms of varix; especially in htemorrhoids, and usu ally, though not always, leads to the coagu lation of the contained blood. 1 have seen .acute inflammation of a varicose saphena causing much interstitial plastic deposit, in which no coagulum formed in the interior of the vessel, whose canal was quite pervious.
Suppurative Phlebitis.—When phlebitis leads to suppuration, it is generally, I believe always, accompanied by plastic effusion also.
The question of pus formation within veins is one of great importance and interest, and -difficult of solution. In a great proportion of examples, purulent phlebitis is originally lighted up by the mechanical introduction of pus into the veins. In some few cases the pus would seem to originate within the vein, either from an ulceration of the inner surface, or perhaps it is secreted free on the unbroken lining membrane. One very remarkable point is the enormous multiplication of the pus within the vein. No absorption, or me chanical introduction, can at all explain the immense increase ; and it is obvious that there exists within the vessel some source of this pus generation. It was imagined by Gendrin and Donne that the blood itself was the source of the pus, and that it was developed by the metamorphosis of blood globules into pus cells ; and they imagined that the change of form to a sphere, which the blood discs un dergo, when submitted to the action of certain fluids, was an indication of the change. This doctrine has, however, been long since ex ploded.
A more reasonable explanation, and one founded upon analogy, is that the pus is se creted by the inner surface of the vein, by a metamorphosis of epithelium. Vogel has long since demonstrated, on the mucous mem branes, that pus is producible by a change of epithelial cells, and this suggests an explana tion, — why, in an unbroken vessel, pus may be produced in great abundance. Wherever epithelium exists, it appears that pus cells may be generated without lesion of surface; espe cially where the action is started by contact of pus from some other source. This certainly
happens in serous cavities,—pleura, pericar dium, &c. ; and we may, from analogy, judge that the same occurs in veins. This doctrine is entertained by the high authority of Hasse : he observes, —" In accordance with these views, the masses, generated within the veins, would be developed as follows : — First of all the cells of epithelium-lining dis covered by Henle, separate from the internal membrane of the vein, so as to give the inner surface of the vessel the dull appearance al ready described, and to render it more sus ceptible of a morbid tinge from imbibition. The _next change affects the passing blood cor puscles, which assume a spheroid or else a gibbous appearance, advance with a slow re volving movement, or cling to one another, parting with their serum and with their pig ment. The internal membrane of the vessel generates new imperfect epithelium cells, which mingle with the altered blood, and finally actual pus-globules, which, when con gregated in sufficient number, completely ar rest the current of the blood, and affect the blood•corpuscles in the manner already pointed out. The simultaneous effilsion of both fibrin and albumen now serves to complete the formation of a plug, which differs in external characters according to its more or less rapid development, and to the varying proportions of its constituent parts. The plug, thus originat ing, afterwards undergoes further changes."* The actual changes that occur, and are ob vious to the naked eye, affect the plastic plug, the fluid contents, and the parietes of the vein. In suppurative as well as adhesive phlebitis, plugs of lymph and coagula are formed, and are partly the result of inflammatory action, and partly they are the direct result of the contact of fluid pus with the blood.t The plugs that form in suppurative phle bitis are softer, more numerous, and vary in form. They soon become broken down, and exhibit disintegrated fibrin mixed with ge nuine pus. The coagula become softened, first in the centre ; they loose their laminated structure, and ultimately break up. These coagula, in phlebitis the result of infected blood, must not be considered as any indica tion of the locality in which the disease has originated. In such cases the whole circu lating mass is infected : little portions of coagu lating fibrin, entangling pus-cells, are con tinually passing through the vessels, and here and there attaching themselves to the lining of the vessel, light up circumscribed regions of inflammation. This coagulation is a re medial effort : by its means the tnateries morbi is shut up and circumscribed by a harmless coagulum : circulation in the affected vessel is suspended and the poison cannot again mix with the blood. Perhaps these coagula some times become absorbed, or organised and ob literate the vessel ; at other times they sup purate, and the walls of the vessel become implicated and ultimately give way. " The formation of matter being brought about with in the inflamed vein, its membranes have like wise to undergo a further change. Their colour now inclines to a greyish white ; they become softened and thickened, are no longer to be distinguished from one another, and form, in conjunction with the surrounding tex tures, a nearly uniform membranous layer of a lardaceous aspect and character. By and by a turbid puriform fluid is often found de posited at intervals in the cellular texture ; in some instances where the suppuration is vi gorous in the vicinity of the vein, the latter traverses the purulent channel for a consider able space, denuded of its entire circumfer ence. Here the membranes of the vein gra dually soften, and at length melt down, so to speak, until no further vestige of their texture is discernible within the common centre of suppuration."* If, however, this circumscrip tion of the pus by means of coarmluin does not occur, and it floats through the vascular sys tem, it produces a variety of secondary effects remarkable and important in their results.