ORGANIZABLE PRINCIPLES. 417 



in the Buffy Coat ( 588), however, that the fibrous arrangement is best seen; 

 on account, as it would appear, of the stronger attraction which the particles 

 of fibrin have for one another, when its vitality has been raised by the increased 

 elaboration to which it has been subjected. That there are varieties of plastic! I \/ 

 in the substance, which, on account of its power of spontaneously coagulating, 

 we must still calljibrin, appears from this fact among others, that, in tuber- 

 culous subjects, the quantity of fibrin in the blood is higher than usual (Andral 

 and Gavarret), although its plasticity is certainly below par. It is easy to 

 understand, that its plasticity may be increased as that it may be diminished ; 

 and this either in the general mass of the blood, or in a local deposit. In 

 fact, the adhesions which are formed by the consolidation of coagulable lyrnph, 

 or in other words, of liquor sanguinis, whose plasticity has been heightened 

 by the vital actions in the capillaries of the part on which it has been effused, 

 often acquire very considerable firmness, before any vessels have penetrated 

 them ; and this firmness must depend upon that mutual attraction of the par- 

 ticles for one another, which, in aplastic deposits, is altogether wanting, and 

 which, in cacoplastic deposits, is deficient. A very interesting example of a 

 structure entirely composed of matted fibres, and evidently originating in the 

 simple consolidation of Fibrin, has lately been discovered by the writer. This 

 is found in the membrane adherent to the interior of the Egg-shell (Membrana 

 putaminis) ; and also in that which forms the basis of the Egg-shell itself. 

 Between the two, there is no essential difference ; as may be seen by examin- 

 ing " an egg without shell," as it is commonly termed, (or rather one in which 

 the shell-membrane has been unconsolidated by the deposition of calcareous 

 matter) ; or by treating the egg-shell with dilute acid, so as to remove the 

 particles of carbonate of lime, which are deposited in the interstices of jhe 

 network. The place of the shell is then found to be occupied by a membrane 

 of considerable firmness, closely resembling that which surrounds the albumen 

 of the egg, but thicker and more spongy. After maceration for a few days, 

 either of these membranes may be separated into a number of laminae ; each 

 of which (if sufficiently thin) will show a beautiful arrangement of reticulated 

 fibres. It is impossible to refuse to such a structure the designation of an 

 organized tissue, although it contains no vessels, and must be formed by the 

 simple consolidation of Fibrin, poured out from the lining membrane of the 

 oviduct of the bird. It is probably in the same manner that the Chorion of 

 the Mammiferous animal originates; since this is a new envelop, formed 

 around the ovum, during its passage along the Fallopian tube. In the latter, 

 for an ulterior purpose, vessels are afterwards developed, by extension from 

 the contained ovum ; and by the nutrition they supply, its size is increased, 

 and changes take place in its texture. But in the Egg-membrane of the Bird 

 there is no need of vessels ; because no subsequent change in its texture is 

 required, and its duration is sufficient for the purpose it has to answer. 



555. The completeness of the transformation of Fibrin into simple Fibrous 

 Tissue, appears to depend upon two circumstances in particular ; the perfect 

 elaboration of the Fibrin itself, and the vitality of the surface upon which the 

 concretion takes place. When the Fibrin is highly elaborated, it will coagu- 

 late in the form of a definite network of minute fibrillaB, even upon a dead 

 surface, as a slip of glass; this is the case, for instance, with the Fibrin of the 

 buffy coat of the Blood, or with that of the Liquor Sanguinis (coagulable 

 lymph), poured out for the reparation of an injured part. But in the ordinary 

 Fibrin of the blood, the fibrillation is less distinct when the concretion takes 

 place upon a dead surface. When it occurs in contact with a living surface, 

 however, the coagulation takes place more gradually ; and it seems as if the 

 particles, having more time to arrange themselves, become aggregated into 

 more definite forms, so that a more regular tissue is produced just as crystals 



