Page:Proceedings of the Royal Society of London Vol 4.djvu/262

Rh threads, which in many places have the appearance of a necklace, but subsequently lose the traces of division, and become cylinders. Schwann had conjectured that the globules just referred to — as ha- ving been observed by V alentin — are cells, and that these cells coa- lesce to form a secondary cell, that is, the muscle-cylinder. The author confirms the observations of Valentin and the conjectures of Schwann, with the addition, that the globules coalescing to form the muscle-cylinder are blood-corpuscles which have become cells. The fibrils appear to be subsequently formed within the cylinder, which thus becomes the muscular fasciculus. The medullary portion of the cylinder appears to be composed of the pellucid objects, one of which is contained within each altered blood-corpuscle. Some of these pellucid objects, however, continue to occupy a peripheral situation.

The author thinks it is not probable that muscular fibre and the chorion are the only tissues formed by the corpuscles of the blood ; he is disposed rather to inquire, how many are the tissues which they do not form ? Nerves, for instance, are known to arise very much in the same manner as muscle-cylinders ; and epithelium-cells sometimes present appearances which have almost suggested to the author the idea that the)'- were altered corpuscles of the blood.

Schwann had prevously shown that " for all the elementary parts of organisms there is a common principle of developement," — the elementary parts of tissues having a like origin in cells, however different the functions of those tissues. The facts made known in the present memoir not only afford evidence of the justness of the views of Schwann, but they farther show that objects, such as the corpuscles of the blood, having all the same appearance, enter im- mediately into the formation of tissues which physiologically are extremely different. Some of these corpuscles arrange themselves into muscle, and others become metamorphosed into constituent parts of the chorion. But the author thinks it is not more difficult to conceive corpuscles having the same colour, form, and general appearance, undergoing transformations for very different purposes, than to admit the fact made known by two of his preceding me- moirs,- — namely, that the nucleus of a cell, having a central situa- tion in the group which constitutes the germ, is developed into the whole embryo, while the nuclei of cells occupying less central situa- tions in the group, form no more than a minute portion of the am- nion. It is known that in the bee-hive a grub is taken — for a spe- cial purpose — from among those born as workers, which it perfectly resembles until nourished with peculiar food, when its developement takes a diflferent course from that of every other individual in the hive.

The Society then adjourned over the Whitsun Recess, to meet again on the 18th instant.