Page:Microscopicial researchers - Theodor Schwann - English Translation - 1947.pdf/140

114 dition in which they immediately attract attention in the investigation of that tissue in the fœtus. We shall in the next place consider the earlier, and then the subsequent stages of their development. In addition to the corpuscles before mentioned, others may be seen in very young areolar tissue, which are not elongated into fibres, but are more or less round. They are granulous and contain a nucleus with nucleoli, and as they present all the stages of transition up to those cells which are prolonged into fibres, we must regard them as being the undeveloped fibre-cells. Various forms of them are delineated in pl. III, fig. 6. I will not assert that all round cells in fœtal areolar tissue are young fibre-cells; for we shall presently become acquainted with some which are not. It is only after the commencement of the process of acumination that the young fibre-cells can be distinguished from these; in the earliest state, when they are as yet quite round, almost all cells are alike. It is difficult to determine positively whether or not these cells are formed around a previously existing nucleus; probably, however, such is the case, as there are no cells to be seen without nuclei, although there are many nuclei observed without investing cells.

The following, then, are the results of our investigation into the progress of development of areolar tissue, in so far as we have as yet pursued it. In the first place, small round cells are formed (probably around a previously existing nucleus), in the structureless jelly-like cytoblastema of the tissue. The cells, furnished with the characteristic nucleus, become acuminated in two opposite directions, and these acuminations elongate into fibres, that sometimes give off branches, and at length split into fasciculi of extremely minute fibres, which, in the early stage, cannot be distinctly perceived to be insulated. As development proceeds, the splitting of the two principal fibres, issuing from the body of the cell into a bundle of more minute fibres, continually advances nearer towards the cell, so that, at a later period, a fasciculus of fibres issues immediately from the body of the cell (see pl. III, fig. 7.) At a subsequent period, this process of splitting reaches as far as the nucleus, and at length goes quite through the body of the cell, and the nucleus then lies merely upon a fasciculus of fibres. At the same time the fibres in the progress of de-