(1) The fine elementary granules constitute by far the great mass of the contents. They are dissolved by alkalies, but alcohol and ether do not effect their solution, and they are little dissolved by acetic acid ; so that they would thus seem to consist of an albuminous substance, or of a so-called protein-com pound. They are immeasurably minute, and in this respect resemble the pulverulent molecules which cause the white colour of the chyle.* Their quantity in the gland vesicles is so large that they render viscous their fluid contents. It is only on the appli cation of water, that they aggregate them selves into masses or flocculi: previously to this they pervade the viscid fluid with the greatest uniformity. We will select for them the name of pulverulent molecules.
2. The fatty granules are usually met with in considerable quantity, and sometimes they are very numerous. As may readily be ima gined, they are of very different diameters, and range gradually from the smallest granules, through larger ones, to small drops of fat. The yellow colour of the cortical substance is due to this constituent.
3. The nuclear structures appear un:ted into a granular mass. They have an average size of 3 to 4-1000ths of a line, a form which is usually roundish and less frequently oval, and they belong to the variety of the so-called " granular" nuclei ; i. e. to those which are formed of a granular mass, and are not vesi cular. The substance of these nuclei is in soluble in dilute acids, but is completely dis solved by the application of potash. Ecker has made the interesting observation, that in the embryo the granular nuclei are no longer to be met with, but that their nuclei are ra ther vesicles ; that is, that they possess a wall, which encloses a more or less fluid mass, in which are contained one or two small punc tiform nucleoli. The same condition also obtains in the nuclei of other embryonal tissues.
4. Part of these nuclei are experiencing a transition to cell development, so as to form a constituent of perfect cells. The metamor phosis to the cell-form begins by a part of the finely granular mass arranging itself around a nucleus. Little clusters are thus formed, each of which contains a nucleus. The outer surface of such a mass then becomes hardened, so that the most super ficial molecules form a wall or shell, the cell-membrane ; thus the cluster becomes a cell. So that from the fine pulverulent molecules proceed both the cell and the cell-membrane. In conformity with this state ment, a microscopic examination of the ex pressed contents of the gland-vesicles reveals nuclei, surrounded by irregular flocculi of fine granular substance (b, fig. 542.), and other
nuclei, around which this latter substance has formed itself into a well-defined, round, or oval mass of 6 to 0-1000ths of a line in dia meter (c, fig. 542.). Finally, other masses may be seen, on which an enclosing mem brane plainly exists.
The cell development just described holds .good of the supra-renal capsules of all Ver tebrate. It is thus of very wide distribution. These cells are designated by the name of globules of circumposition (unthulhingskugeln). The so-called granule-cells, or inflammatory globules, belong to the same class ; as also do the globules of fission which originate from the breaking up of the yolk. And I have also observed that the polyhedral pigment cells of the choroid coat of the eye are formed in the same way. Finally (and of immediate interest in this place), I have found that the cells of many other glands are similarly formed ; namely, the cells of the tubular gastric glands, the glands of Lieberkuhn and of the large intestine, the glands of Brunner, and probably also those which occur in the uri nary tubules of the kidney. It may also be conjectured that the cells of other glands will be found to originate in the same way.
By a gradual enlargement these cells of the cortical substance are metamorphosed into gland-vesicles (e, fig. 542.); so that while in the large gland-vesicles cells and nuclei occur in numbers, the smaller ones contain only a solitary nucleus. These smallest gland-vesicics are no way distinguishable from the larger cells; they also are cells, and the glandular con tents are exactly those of the cell, and the membrana propria is identical with the cell membrane. The contrast between these vesicles and cells — a contrast upon which Ecker has laid particular stress — is of little importance. According to this observer, the membrana propria of the vesicle is unchanged by solution of potash, while, on the contrary, the membrane of the cell is dissolved by it. But by a repetition of the experiment one may be assured that it is only a dilute solution which leaves the membrana propria unaffected, and that by a more concentrated solution it is dissolved just as much as the cell-membrane. The diffirence is thus only quantitative, and is in exact conformity with the gradually increasing hardness of the mem brane.