320 SEROUS MEMBRANES. 



elsewhere, we may indeed infer that it tends to assume the form 

 of a membrane roughened by villosities. But this tendency is 

 counteracted on the one hand by the repeated mechanical dis- 

 turbances to which it is exposed, while on the other it is rendered 

 impossible at most points by the superimposed layer of fibrin. 

 Hence the granulation-tissue forces its way up into all the inter- 

 stices of the fibrinous stratum, grows round it and through it 

 layer by la}'er, and thus attains a considerable degree of thick- 

 ness earlier than it would otherwise have been able to do. Not- 

 withstanding even this intimate penetration, in which the fibrin 

 acts the part of a supporting framework, w^e must reject any 

 claims to an active share in the organising process, wdiich may 

 be urged on its behalf. 



Close upon the heels of this development of embryonic tissue 

 comes vascular isation. An extraordinarily rich network of capil- 

 laries speedily permeates the young false membrane. The newly- 

 formed vessels are characterised by their exceptionally wide 

 calibre, and as is often the case with young vessels, by the thin- 

 ness of their walls. On the other hand, the afferent and efferent 

 vessels of the serous membrane are few and narrow. The result 

 is an arrangement resembling that of the retia mirabilia, where 

 the blood-pressure is proportionately heightened by the interven- 

 tion of a capacious channel between an afferent and an efferent 

 vessel. A like result may be anticipated in the present instance ; 

 — and that the blood in the newly-formed capillaries is really 

 under a far higher pressure than in those of the serous membrane, 

 is proved by the number of extravasations wdiich ensue both in 

 the interior, and upon the surface of the false membrane, giving 

 it a reddish and mottled colour ; while the free fluid is likewise 

 tinged with red. Accordingly, the vascularisation of the false 

 membrane leads in the first place to a state of things most critical 

 as regards the general course of the disease — a state of things 

 wdiich not only affords the most favourable conditions for the 

 continuance of the exudative process, but also, by supphing 

 an abundance of nutrient matter, favours to the utmost the 

 formative changes in the false membrane itself. At this point 

 therefore, the patient is threatened with an over-production of 

 cells — with suppuration. The practitioner detects the unfavour- 

 able turn the disease is taking, and expresses his fears by saying 

 that it drags, that absorption has come to a dead-lock, &c. 



