VEIN. 



1393 



certain conditions winch must occur before 

 coagulation can develop itself. While the 

 blood, itself in a state of health, remains in 

 contact with the lining membrane of healthy 

 blood vessels, coagulation is impossible ; but 

 under certain conditions of disease the blood 

 loses its fluidity, and these conditions may 

 either consist in some abnormality of the ves- 

 sel's walls, or in some foreign matters becom- 

 ing mixed with the blood, the former in- 

 fluence being passive, and the latter an active 

 agent in producing or hastening coagulation. 



I would here urge the doctrine that the 

 vascular cavity, the hollows of all the tubu- 

 lar vessels (veins, arteries, and lymphatics), 

 together with the ventricles and auricles of 

 the heart, constitutes a true serous shut 

 sac, much complicated in form and modified 

 by its peculiar functions, it is true ; but pos- 

 sessing the same anatomical elements, an 

 epithelial pavement placed upon a sheet of 

 limitary tissue, on the other side of which is 

 situated a nutrient vascular system. I would 

 here urge this view, because it applies with 

 much force to certain questions in venous 

 pathology, and to few more so than the one 

 under consideration, where arguments by 

 analogy are a desideratum. The lining mem- 

 brane of the veins then is a serous membrane. 

 On the surface of other serous membranes 

 pleura, pericardium, c. plastic effusion con- 

 sists of sheets of lymph, and a certain amount 

 of serum. By analogy we, priori, conclude 

 that lymph is effused in inflammation on the 

 lining surface of the veins, and this the experi- 

 ments of Gendrin and Mope have established 

 by indisputable proof. That the inflammatory 

 product consists partly of serum as well as 

 lymph is supported by analogy alone ; but 

 if admitted would explain the coagulation 

 of the blood to complete the clot, which is 

 known to be so much facilitated by the ad- 

 mixture of foreign or abnormal secretions. 

 Whatever may be the opinion of the forma- 

 tion of the coagulum, its characters are these : 

 it consists of concentric laminae, brownish, 

 yellowish, or white, of which the central are 

 the darkest and softest; and sometimes the 

 centre is nearly fluid blood. The density of the 

 entire clot is subject to much variety. The 

 coagulum is moulded to the cavity of the vein, 

 and sometimes present the exact impression of 

 the valves. Mr. Arnott has made an interesting 

 observation with respect to the coagulum, 

 that it extends along the affected vein usu- 

 ally to the next collateral branch, and there 

 abruptly ceases. The true explanation of 

 this circumstance is doubtless that given by 

 Mr. Henry Lee.* " When any portion of 

 a vein is obstructed, the blood is kept at 

 rest between the obstruction and the next 

 collateral branch ; and, if disposed to coagu- 

 late, there is nothing to interfere with such 

 an action. But the case is different as soon 

 as one vein opens into another. A fresh cur- 

 rent of blood is then continually sweeping the 



* On Phlebitis and Purulent Deposits, bv Henry 

 Lee, Lond. 1850, p. 23. 



VOL. IV. 



orifice of the obstructed vessel; and even 

 although the blood at this point should have 

 a tendency to coagulate, it is carried on in the 

 course of the circulation, before it can adhere 

 to the sides of the unobstructed vein." 



The coagulum thus extends towards the 

 heart, beyond the limits of the inflamed por- 

 tion, having a mere mechanical boundary. It 

 extends also at the distal end, but here it 

 becomes gradually attenuated : it often rami- 

 fies into many branches and subdivisions of 

 the veins that are tributary to the one ob- 

 structed, especially where they are not re- 

 lieved by collateral anastomoses. At those 

 points where inflammation has not occurred, 

 and the coagulation has been favoured by me- 

 chanical circumstances simply, the clot scarcely 

 adheres to the lining membrane of the vein. 



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 cel.ular 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. -j- 



These phenomena may occur in veins of 

 any size ; and to any extent in am particular 

 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 



* See Cooper and Travers's Essays, Lond. 1818, 

 part i. plate 10. 



t Hasse's Pathological Anatomy, Sydeuhaui So- 

 ciety's translation, Lond. 18-16, p. 13. 



4 u 



