238 MARTIN BARRY ON FIBRE. 



In mammalia, including man, this filament is frequently annular ; 

 sometimes the ring is divided at a certain part, and sometimes one 

 extremity overlaps the other. This is still more the case in birds, 

 amphibia, and fishes, in which the filament is of such length as 

 to constitute a coil. This filament is formed of the discs contained 

 within the blood-corpuscle. In mammals, the discs entering into its 

 formation are so few as to form a single ring ; and hence the biconcave 

 form of the corpuscle in this class, and the frequently annular form of the 

 filament it produces. In the other vertebrata, the discs contained 

 within the blood-corpuscles are too numerous for a single ring ; and 

 they consequently form a coil. At the outer part of this coil, the fila- 

 ment, already stated to be flat, often presents its edge ; whence there 

 arises a greater thickness of the corpuscle, and an appearance of being 

 cut off abruptly at this part ; while in the centre there is generally 

 found the unappropriated portion of a nucleus ; and hence the central 

 eminence, surrounded by a depression, in those corpuscles which, from 

 the above-mentioned cause, have the edge thickened. The nucleus of 

 the blood- corpuscle in some instances resembles a ball of twine, being 

 actually composed, at its outer part, of a coiled filament. In such of 

 the invertebrata as the author has examined, the blood- corpuscle is like- 

 wise seen passing into a coil. 



The filament, thus formed within the blood- corpuscle, has a remark- 

 able structure ; for it is not only flat, but deeply grooved on both sur- 

 faces, and consequently thinner in the middle than at the edges, which 

 are rounded ; so that the filament, when seen edgewise, appears at first 

 sight to consist of segments. The line separating the apparent seg- 

 ments from one another is, however, not directly transverse, but ob- 

 lique. 



Portions of the clot in blood sometimes consist of filaments having a 

 structure identical with that of the filament formed within the blood- 

 corpuscle. The ring formed in the blood- corpuscle of man, and the 

 coil formed in that of birds and reptiles, have been seen by the author 

 unwinding themselves into the straight and often parallel filaments of 

 the clot ; changes which may be also seen occurriifg in blood placed 

 under the microscope before its coagulation ; and similar coils may be 

 perceived scattered over the field of view, the coils here also appearing 

 to be altered blood- corpuscles, in the act of unwinding themselves ; fila- 

 ments, having the same structure as the foregoing, are to be met with 

 apparently in every tissue of the body. The author enumerates a 

 great variety of organs in which he has observed the same kind of fila- 

 ments. 



