On fibre

The author observes, that, in the mature blood-corpuscle, there is often seen a flat filament, already formed within the corpuscle. 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 frequent annular form of the filament it produces. In the other Vertebrata, the discs contained within the blood-corpuscle are too numerous for a single ring ; and they consequently form a coil. At the outer part of this coil, the filament, 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 likewise seen passing into a coil. The filament, thus formed within the blood-corpuscle, has a remarkable structure ; for it is not only flat, but deeply grooved on both surfaces, 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 segments from one another is, however, not directly transverse, but oblique.