Elder cells thus seem (within certain limits) to cause the increase. and regulate the qualities, of younger ones. Younger cells are, on the other hand, more or less active agents in effecting the destruction of the elder ones : less so in endogenous Growths, where the elder may increase materially in size (as their contained brood multiplies), and acquire thickened walls ; more so in exogenous Growths, where such enlargement of cells is not witnessed, and where the production of young is coeval with the disintegration of old ones.
Such are the modes of production and in crease of cells, considered in their general relations to themselves and to the mass they form. We must now view cells as individual existences, and inquire into the process by which they are each developed ; and our knowledge of this process is as yet limited and unsettled. The spherical cell appears to be produced on three distinct plans. (a) Gra nular matter, precipitated from the fluid blastema, accumulates sufficiently to form a minute solid body (cytoblast or nucleus), from and around which the cell-wall forms.
(b.) The cell is a molecular hollow body from the first, and, as it grows, produces within itself, or in its wall, a secondary body, the nucleus,— the cytoblast of a future cell.
(c.) The cell is, from the first monient of its existence, complete in all its parts, consisting of a cell-wall, a nucleus, and fluid contents ; its development consists in the progressive and justly-proportioned increase of all these elements. The caudate cell is held to arise (as already hinted) from the prolongation of opposite points of the wall of a spherical cell ; but there is no proof that cells may not exhibit this shape from the first moment they are possessed of form at all. Lastly, the ele mentary fibre is held to be formed in three different modes. (a.) A spherical cell having undergone elongation so as to become cau date, loses by still increased elongation and flattening, the • characters of a hollow cell altogether ; a nucleated fibre is the result. (b.) Elongation and linear juxtaposition of nuclei effect the formation of fibre. (c.) Or, it is held, fibres form as such from the first moment shape is assumed ; no cell, or nucleus-stage having pre-existed. All these points are yet sub judice.
The plan of enlargement and mode of arrangement of the ultimate elements of Growths seem to exercise a very distinct in fluence on the structural character of the mass as visible to the naked eye. The locular
aspect of their divided surfaces, for instance, w e fully believe to be dependent on such influence. In the case of Growths enlarging on the endogenous plan, it is obvious that the juxtaposition of successive round cells within a containing or parent cell must cause this to retain its spherical outline, until it has en larged sufficiently to become visible with the naked eye ; and further, that if several of these enlarged cells be placed round a common centre and beside each other, the general form of the area they cover must be spherical. And so we find that it is precisely in enehon droma and in colloid cancer, distinctly en dogenous formations, that sphericity is most decided. The thickening and fibrous depo sition, which take place both in the walls of enlarged cells and in the intercell substance, contribute further to the deceptive appear ance of encysted structure. In masses which enlarge on the exogenous plan, the spherical character in the loculi is much less apparent. In scirrhus, and in many specimens of ence phaloid, it is not to be clearly descried ; the pre dominance of straightly-fibrous arrangement of the stroma, produced by the presence of real fibrous tissue, of fusiforin corpuscles, &c., accounts for this. But even in Growths of this class, the original rounded form of the elementary constituents tends to irnpress upon their larger divisions, as these do upon the entire mass, the spherical shape. Accidental circumstances, of course, are liable to affect this ; but the internal locular arrangement of fibrous tumours shows that those circum stances may be only partially effectual.
The 'ocular character (under the title of " encysted ") has been put forward as an evidence of "malignity" on the part of the structure exhibiting it. Experience proves the notion to be untenable. Sphericity of the loculi is most obvious in enchondroma, one of the most intrinsically innocent Growths known ; such sphericity is, on the other hand, totally, or almost totally, wanting in scirrhus and many specimens of encephaloid. Again, the least deleterious form of cancer — col loid, exhibits it in an especial manner ; and, though modified, it is evident in those pecu liarly benignant structures (considered in their essence) fibrous tumours.