Dr. Buchanan on ther fibrin contained in the Animal Fluids. 135 



tho same attractive power, to dimiDish in size, and some of the con- 

 stituent corpuscles contracting more than others, their appearance is 

 variously altered and disguised. 



Tho process of coagulation, then, seems to be a very simple one, 

 consisting in the aggregation of the fibrinous globules and granules 

 diffused through the liquid, bj a force perhaps little different from 

 cohesive attraction. The observations recorded below, lead to the 

 same conclusion as to tlie nature of the process in other instances. 

 In all probability, the reason why the fibrinous globules do not coagu- 

 late within tho vessels and cavities of the body is, that they are kept 

 in equilibrium by the attraction of the contiguous tissues, which being 

 themselves made up of similar corpuscles, probably possess a similar 

 attractive power; but when the coagulable liquids are withdrawn 

 from the body, the antagonist power is destroyed, and the fibrinous 

 globules, under the influence of mutual attraction, are aggregated 

 into a mass. 



If the coagulum first perceived in the blister liquid be removed 

 immediately, free globules will still be observed in the liquid, and by 

 and by a fresh coagulum will form ; and thus several successive 

 coagulations may take place, before the liquid is seen altogether 

 deprived of its globules. 



5. Formation of Jilaments, and reticular tissue in substance of coagu- 

 lum. — After complete coagulation, the primary vesicles are no longer 

 observed, their cavities being obliterated, and the membranous 

 parietes converted into short solid filaments, inextricably interwoven 

 with each other. On the first concretion of the fibrinous mass, it is 

 voluminous, extending over the whole space occupied by the consti- 

 tuent vesicles and their interstices. It soon, however, contracts to 

 a smaller size, and the rapidity of the contraction is much accelerated 

 by mechanical agitation, as by drawing the coagulum out of the liquid. 

 After contraction, it has lost its transparency, and has the form of an 

 opaque white membrane or thicker mass. In a thin shred of this 

 mass placed under tho microscope, the vesicles of which it at first 

 consisted, are found to have disappeared, leaving a homogeneous 

 structure, of which from its density the constituent filaments are with 

 difficulty perceived. Sometimes again distinct vesicles are seen here 

 and there imbedded in tho coagulated mass. 



Tho mode of formation of tho reticular tissues, or those which have a 

 basis of cellular membrane, does not appear to me to be, as it has been 

 described by Schwann, by the division of vesicles elongated into fila- 

 ments. No such process of division is ever seen in the fibrinous 

 vesicles, while every mass of fibrin, from the moment of its formation, 

 seems to affect the reticular form. Instead of this reticular form 

 depending upon the arrangement of the parts of single vesicles, it 

 depends on the arrangement of the vesicles in relation to each other, 

 which, whether they retain their vesicular shape, or what more gener- 



