ADHESION. 



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. 



The experiments of Brande* would, however, 

 lead to a different conclusion ; he shewed that 

 the air contained in the blood had much in- 

 fluence in the formation of bloodvessels. This 

 air is carbonic acid gas, and its quantity appears 

 to be nearly equal in the two kinds of blood ; 

 being estimated at a cubic inch for every ounce 

 of blood. This gas maybe separated from the 

 blood by the air-pump, and it escapes with a 

 kind of bubbling or effervescence, causing the 

 ascent of the mercury in a barometer attached 

 to the apparatus. 



It has been remarked that during the coagu- 

 lation of the blood, a large quantity of carbonic 

 acid gas escapes; this coagulation, observed 

 under the microscope, has shewn that the gas, 

 by escaping in all directions, forms a net-work 

 of canals, the branches of which anastomose 

 with each other ; and that this net-work pre- 

 serves its form after desiccation. It has also 

 been established that it is this gas which forms 

 those canals in coagulated blood ; because, if 

 by means of the air-pump we deprive the blood 

 of it, before it is coagulated, they do not occur. 



Sir E. Home has even injected the vessels 

 which were developed in the coagulum soon 

 after the blood was taken from a vein. If the 

 formation of new vessels occur even in a coa- 

 gulum of blood removed from the living body, 

 but preserving still a certain quantity of its 

 heat, and of its vitality, with more reason might 

 we expect that a similar phenomenon should 

 obtain during life : and this fact has been de- 

 monstrated by experiments performed on a 

 rabbit, in which had been produced a hemor- 

 rhage from a small branch of the mesenteric 

 artery : after twenty-four hours, the coagulum 

 which was formed was injected. 



The formation of vessels in coagulated blood, 

 by means of the carbonic acid gas which tra- 

 verses it in all directions, is in perfect accord- 

 ance with the observations which have been made 

 by M. Bauer upon germinating wheat, which 

 were instituted for the purpose of shewing the 

 influence of the globule of air. These globules 

 are manifested below a bud of mucilaginous 

 substance ; they push it forward, elongate it, 

 and thus form a filament. 



I do not, however, believe that either of 

 these theories correctly explains the pheno- 

 menon. 



It was for a long time believed that false 

 membranes were never organised ; that nature 

 had given to the parts of our economy an 

 almost unlimited power of development, but 

 not the faculty of communicating life to the 

 products of the circulation; that false mem- 

 branes appeared to be organised only because 

 they constituted a kind of frame-work through 

 which vessels from the inflamed tissue might 

 be prolonged : ulterior observations, however, 

 have shewn that these media are really or- 

 ganised. We have no general rules as to the 



time when such organisation shall commence. 

 It seems to be dependent upon inexplicable 

 individual dispositions. It may, however, be 

 remarked, that the greatest analogy exists be- 

 tween the mode of development of vessels in 

 these media of adhesion and their mode of 

 production in the membrane of the yolk in the 

 chick, saving always this remarkable circum- 

 stance, namely, the inconstancy, the irregu- 

 larity of the work of organisation in the former, 

 and, on the contrary, the constancy and the 

 regularity of the occurrence in the latter 

 case. 



These media are in fact secreted by a tissue, 

 the vitality of which is exalted to a certain 

 extent, and it appears to impress upon the pro- 

 duct of its secretion a commencement of vitality, 

 as in generation. All these circumstances ap- 

 pear to me to demonstrate that these vessels are 

 the product of a spontaneous generation a true 

 epigenesis ; so indeed, to a certain extent, 

 thought Hunter. lie says, " In a vast number 

 of instances I have observed, that in the sub- 

 stance of the extravasation there were a great 

 number of spots of red blood, so that it looked 

 mottled. The same appearance was very ob- 

 servable on the surface of separation between 

 the old substance and the new, a good deal 

 like petechial spots. Was this blood extra- 

 vasated along with the coagulating lymph ? 

 In this case I should rather have supposed it 

 would have been more diffused. I have there- 

 fore suspected parts have the power of making 

 vessels, and red blood, independent of the 

 circulation."* 



If the inflammation be not strictly confined 

 to that state in which the albumino-fibrinous 

 exhalation is accomplished, but proceeds to the 

 next stage, the exhalation entirely changes 

 character ; pus is produced, a granulating sur- 

 face is developed, and union is accomplished 

 by the intervention of another tissue, and by a 

 slower process than that which we have already 

 described. This is the process which is always 

 observed in mucous membranes, scarcely ever 

 in serous; for in the former, the albumino-fibri- 

 nous matter never becomes organised, and can 

 therefore never be the medium of a permanent 

 union. In these membranes, if adhesion occur, 

 the inflammation must proceed to the succeed- 

 ing stage. Adhesion of mucous membranes, 

 however, does not often occur it is not com- 

 patible with the performance of their functions. 



Soon after the secretion of pus is established 

 granulations are developed, and a state favour- 

 able to adhesion is produced. The develop- 

 ment of granulations occurs in the following 

 manner : upon the surface, about to suppurate, 

 is exuded a layer of" coagulable lymph ;" this 

 lymph becomes penetrated by bloodvessels, 

 nerves, and absorbents, which give birth to 

 granulations. These granulations are developed 

 much earlier in some tissues than in others 

 in a stump, for instance, we see them first 

 upon the cellular tissue, then upon the mus- 

 cular, then the fibrous, and lastly upon the 

 osseous tissue : they appear to form as much 



Phil. Trans. 1818. pp. 172 and 185. 



* Loc. cit. pp. 388-9. 



