The Parietes Of The Vesicle, whatever may be the nature of the contents, are uniform with the sheath of the nucleus. They resist the influence of acetic acid, or else the latter occasions thickening of the membrane, and a sharper contour of the vesicle. An examination of the contents is essentially facilitated by the following occurrence: In the above summarily mentioned fluids, there probably is always, freely suspended, a reddish glistening fluid or viscid substance, both in little globules, and in larger masses, moulded into various forms, and, where the current is impeded, divided into smaller portions. This substance is rapidly dissolved by acetic acid. It forms the contents of nuclei, and also of cells, - very commonly of cells the recipients of the brood-nuclei of the thyroid gland vesicle, the brood-nuclei of young cysts, - sometimes the contents of pus-cells, and of young cells generally. Here, again, it is, together with the very delicate cell-wall, soluble in acetic acid. In like form we often observe, especially in the contents of cysts, a colorless, viscid substance, equally soluble in acetic acid, and probably identical with the ordinary colorless cell-contents.

These two substances are, to all appearance, unimportant modifications of the same material. Colorless elementary granules and nuclei, after evaporation of their surrounding watery medium, when placed under the influence of liquor potassse, swell, and assume a reddish tint; we might, therefore, fancy that a difference in density determined the modification, the reddish gleam being simply due to a diminution of density.

The colorless (denser) contents are coagulated by the addition of acetic acid, becoming still denser, bereft of transparency, opalescent.

Akin to this change is that of conversion into a colloid substance.

Occasionally a fatty transition is suffered.

Let us now proceed to pass in review those phases of the cyst, as a structureless vesicle, which we have set down as anomalies of its development.

(a.) In the first place, numerous cysts, like the brood-nuclei and cells they frequently contain, break up, in their primitive state, as structureless vesicles. This is occasionally preceded by a dehiscence and emptying of the vesicle. In other cases, the contents of the cyst are first converted into fat, a transformation of the cyst to a growth resembling the granule-cell.

(b.) Cysts developed within a fluid [the fluid contents of a cyst], for lack of attachments, and of certain textural elements accruing to the structureless membrane from without, do not overstep the primitive condition. They succumb to the processes of involution already described, or enter upon changes hereafter to be explained.

(c.) A remarkable arrest in the cyst's growth attaches to the endogenous development of secondary and tertiary vesicles, resulting in those laminated cyst-growths destined to undergo early incrustation. The lamination may be restricted to a system of many-sheathed or encased vesicles, developed out of either central or extra-centrical, parietal nuclei. Or else several distinct laminated systems occur within a common peripheral one, several nuclei, simultaneously or independently developed within a secondary or tertiary vesicle, having expanded into vesicles, and these, again, generated their own proper central or extra-centrical nuclei. This explains the frequent deviations from the spherical or oval forms. The size of these growths varies greatly. We may have nuclei in which a nucleus-corpuscle is inflated to a vesicle simply bordering upon the contour of the nucleus, or, again, of 1/5th of a millimetre in diameter.

(d.) Another arrest of the development of a cyst, fraught with its eventual destruction, consists in the conversion of its contents into colloid. The cyst becomes reduced to a sheathless colloid mass, becomes fissured or furrowed, and so broken up into fragments. In laminated vesicles, this transformation may affect all the vesicles uniformly or unequally, often a single, and that generally the central one, which, in this case, generates no further nucleus, so that all ulterior lamination ceases.

The consolidation to colloid affects the contents, not alone of the cyst, but also of its basis, the nucleus, and the elementary granule of nucleolus. This we observe alike where cysts are involved in the said conversion, and also under circumstances where no cyst-development takes place beyond a slight extra-normal inflation of the nucleus. Such transformed elementary granules and nuclei occur in medullary cancers.

(e.) Next akin to colloid conversion is the incrustation of the cyst, and of its bases (the nucleus and elementary granule) with phosphate and carbonate of lime. It affects both simple and laminated cysts. These incrusted growths vary from the bigness of a nucleolus and a nucleus, to 1/5th, or even 1/2 of a millimetre in diameter. They are, however, most commonly of about 1/25th to 1/20th of a millimetre. They are identical in form with the simple and laminated cysts, namely, spherical, oval, smooth or nodulated, lobulated, spindle-shaped, or cylindrical, occasionally hourglass-shaped, trefoil-shaped, facetted.

On compression, they frequently split up into regular flaky or wedgelike sphere sections, a circumstance connected, no doubt, with the capabilities of colloid substances to split asunder according to determinate radial systems. At other times they break up into smaller roundish stellse, or into wedge-shaped fragments.

In laminated cysts the incrustation is wont to commence with the innermost layers, where the colloid consolidation of the cyst's contents begins. From hence it proceeds to the external layers. Many incrustations are seen in which the outer layer is as yet free, the incrustation, as seen from above, appearing to surround it as with a light fringe. In vesicles with several collateral filial vesicles, the latter become in-crusted - beginning in like manner with the inner layer - whilst the parent cyst and its layers remain free for some time longer.

It occurs originally either in molecular or in crystalline form, the completed incrustations displaying, now a stellate, now a crystalline, stratiform aggregation.

To sum up, it would appear that it is not the cell out of which the cyst becomes developed, but the nucleus, and that this latter again is evolved, through endogenous growth, out of the nucleolus or elementary granule.

Lastly, that the structureless cyst-wall is not, as we once supposed, an independent textural development.