In all cases, whether two naturally separate tissues are to be united, or whether a solution of continuity is to be repaired, there appears to be a certain uniformity in the means by which the union is accomplished. Inflammation is developed, and a material susceptible of or ganization is exhaled, which becomes the con necting medium. This matter in its greatest state of simplicity is exuded under the form of lymph, upon the surface of the parts to be united ; it is coagulated, and transformed into a soft pulp ; it gradually increases in density, acquires a reticular or porous aspect, a first rudiment of organization, and as a second de gree exhibits in its substance red spots, then striae, which have the appearance of vascular ramifications, and at last bloodvessels.
It is hardly possible to collect this lymph in a state of purity except in the canal of an artery where it has been exhaled between two ligatures. It is then presented under the form of a whitish matter, of a soft and fibrinous consistence,which is rendered particularly evident when the lymph is submitted to the action of boiling water; it dissolves almost completely in a warm solution of caustic potash, though less promptly than thickened albumen, but more rapidly than fibrine.
This matter, which is probably the same with that by which all parts of the body are nourished and preserved, but in the case before us secreted in increased quantity and preserving a strong tendency to coagulate, has nothing in it which is necessarily opposed to the healthy action of the animal economy. In fact we may consider exudation as a nutrition, much exalted by in flammatory action, which is itself only an exaltation of the vital properties.
We may admit four periods or states of change to which this material which consti tutes the medium of adhesion is subject— a first, the period of development ; a second, a period of increase ; a third, that of organi zation; and a fourth, that of mutation ; in which it is changed into a cellular tissue.
In the first period, we find that in twenty four, and sometimes even in nineteen hours after we have irritated a serous membrane, the pleura of a dog, or of a rabbit for instance, that this membrane is much injected, and that there has been formed upon its surface an extremely thin, pulpy stratum, which may very easily be removed : the second period commences when this exudation has assumed a membraniform appearance, and is characterized by an aug mentation of thickness and of density : the third period is characterised by still greater density and the presence of vessels. Stoll believed that these membranes might become organised in twelve, nine, or even eight days after the inva sion of the disease. Home believed that vessels might appear in twenty-four hours.
In the fourth period, the membrane loses some of its thickness, and every day assumes more and more of the appearance of cellular tissue ; and when perfected, there is not only identity of appearance between cellular tissue and these membranes, but also, according to Laennec,* identity of use, and even of disease, except that this tissue very rarely contains adi pose matter.t Nothing in our subject is more curious or more important than the organisation of these membranes ; their vessels are thin, delicate, and similar to those of the pia matey ; their form and their direction are extremely simple ; they are not tortuous, and they proceed, usually, in fasciculi, almost like the lymphatics of the extremities. We may easily convince ourselves
that their formation is sometimes very prompt, by the perusal of the following case. A por tion of strangulated intestine, which, after the incision of the herniary sac, did not present many bloodvessels, was examined after the death of the individual, which occurred in twenty-nine hours after the operation, by Sir Everard Home : he found the portion of in testine which had been strangulated profoundly inflamed, and covered in many points by a " layer of coagulable lymph " this intestine was injected with very fine size, and two small bloodvessels were found passing along through the new membrane into which the injection had penetrated.
According to Laennecs we may observe the following phases in the organisation of these membranes.
The rudiments of bloodvessels are at first presented under the form of striae of blood, which are more voluminous than the vessels by which they are to be succeeded. The blood appears to have penetrated into the tissue of the membrane, as if pushed by a strong injection ; yet in examining the points of the membrane,on which the layer of" coagulable lymph" is depo sited, we find no destruction, nor any orifice of a vessel, but only spots of blood. Soon, ac cording to Laennec, " these lines of blood take a cylindrical form, and ramify in the manner of bloodvessels, still preserving a considerable diameter. If, at this epoch, we carefully ex amine them, we find that these vessels have an external coat which is soft, and formed of blood scarcely concrete, to which they owe their colour. After having incised this coat, we withdraw a sort of mould, or rounded fasci cular body, whitish and fibrous, evidently formed of concrete fibrine, and of which the centre appears perforated and permeable to the blood. However small be the canal, it is these fibrous fasciculi which should, by thinning, form the tunics of the bloodvessels." These delicate observations have not, so far as I know, been confirmed by other observers : those authors who have spoken of newly deve loped vessels, among whom we may name Hunter, Monro, Soemmering, do not speak of this mode of development. Hunter and Home explain it differently; they say there is at first a formation of small ampullae, containing only a colourless fluid : second, a union of these ampullae, and production of a vascular net work, not yet supplied with blood : third, an inosculation between the newly developed vessels, and those of the inflamed membrane, and next the ingress of blood. Beclard was of the same opinion:I- Gendrin thinks that the new vessels are developed by the action of the primitive vessels ; he says, " that the blood is excreted by the adjoining capillaries, opening into the soft and fibrinous tissue deposited in the inflamed part; this blood becomes concrete, and the vascular impulsion, a tergo, being con tinued, new blood is pushed into it and hollows it. Thus the little vascular rudiment is pro longed into an irregular, flexuous, and unequal stria, which meets, another and unites with it, continuing in this way to prolong itself into the least resistent portion of the fibrinous de position."T To some extent the opinions of Laennec and Gendrin are alike ; they believe that the forma tion of the new vessel consisted in this, that the little clot was perforated, and that it was pene trated by liquid blood.