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if this opinion be the correct one, we should have to deal with a process which, whilst advancing from lamella to lamella, each time moved a little farther on. Only the cornea is not composed of perfect lamellae, but of layers, which certainly are on the whole placed one against the other in a lamellar form, but yet are connected with one another; they do not lie any how, more or less firmly or loosely upon one another, but there exist direct connections between them. It is therefore rather a large coherent mass, which is interrupted in certain directions by cellular elements, just as is the case in the very different tissues which we have already specially considered. A vertical section discloses spindle-shaped cells which anastomose with one another, but at the same time also possess lateral processes; and in consequence of their being regularly imbedded in the basis-substance, this lamellar, foliated or plate-like arrangement of the whole tissue is produced. When viewed upon the surface, in horizontal section, they shew themselves in the form of many-rayed, stellate but very flat cells, which may be compared to bone-corpuscles.

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Fig. 101. Horizontal section of the cornea, parallel to the surface and shewing the stellate,flat corpuscles, with their anastomosing processes. From His, loc. cit., fig. II.

PARENCHYMATOUS KERATITIS.

305

If now in this case of ours we follow the process with a higher power, we discover, what may easily be shewn to be the case in every form of keratitis, that the change is essentially seated in the corpuscles or cells of the cornea, and that in proportion as we approach the clouded spot either from without or within, the little narrow cells continually become larger and more cloudy. At last we find them presenting almost the appearance of sacculated canals or tubes. Whilst this enlargement of the elements, this acute hypertrophy, if you will, is going on, the contents of the cells are at the same time becoming more cloudy, and it is this cloudiness of the contents which in its turn occasions the opacity of the whole coat, for the proper basis-substance appears to be

Fig. 102.

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altogether unaffected. This cloudiness of the contents is in part occasioned by particles which are of a fatty nature, so that the process seems to have begun to assume

Fig. 102. Parenchymatous keratitis (cf. Fig. 99), seen with a higher power. At A the cornea-corpuscles in a nearly normal condition, at 11 enlarged, at C and I) still more enlarged, and at the same time clouded. 350 diameters.

the character of a degenerative disease. I should have had no hesitation in believing that a destruction of the cornea had here really set in, but Herr v. Graefe assures me that, from what he has seen, such conditions may, when the disease runs a favourable course, terminate in resolution. And there is really nothing at all in the matter at variance with this possibility; for, since the cells still exist and the only thing required is that their changed contents be got rid of, a complete restitution may no doubt take place.

Now just this doctrine of a simply nutritive restitutional power is of very great importance practically. In such a case as this, where nothing has taken place excepting that the cells, without ceasing to display their activity, have accumulated in their cavities a larger quantity of material than usual, everything is prepared for the process which we call reabsorption; the cells can transform a certain quantity of the material and convert it into soluble substances, and the material in this form may disappear in the very same way in which it came. The structure in the main remains the same all the while; nothing foreign has thrust itself in between the parts; the tissue presents throughout its original constituents.

From the phenomena of this nutritive irritation direct transitions to incipient formative changes are often seen. If namely, we follow up the higher degrees of irritation which take place in a part, we find that the cellular elements, shortly after they have experienced the nutritive enlargement, exhibit further changes which begin in the interior of the nuclei, generally in such a manner that the nucleoli become unusually large, in many cases somewhat oblong, and sometimes staff-shaped. Then as the next stage we usually see that the nucleoli become constricted in the middle, and assume the form of a finger-biscuit (Bisquit), and a little later two nucleoli are found. This division of the nucleoli is an indication of the impending constriction, and afterwards the real division, of the nucleus takes place, as we have already seen in colourless bloodand pus-corpuscles (Figs. 11, A, b; 56, 63). Here we manifestly have to deal with something essentially different from what we had before. In the simple hypertrophy consequent upon nutritive irritation, the nucleus may remain quite intact; here, on the other hand, we frequently see that the contents display a relatively slight amount of change, the utmost being that the cells become larger, whence we infer that a quantity of new material has been taken up into them.

FORMATIVE IRRITATION. DIVISION OF NUCLEOLI. 307

division of the nucleus itself, and the next stage is, that about such a divided nucleolus the finger-biscuit-like

Fig. 103.
A

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In many cases the changes are limited to this series of transformations, of which the division of the nucleus must be regarded as the conclusion. This may be repeated, so that three, four or more nuclei arise (Fig. 15, b, c, d). Thus it comes to pass that we sometimes find cells—not merely in pathological conditions, but also not unfrequently where the development is altogether normal—which contain twenty to thirty nuclei or more. Recently in the marrow of bones, especially in young children, cells have been observed, where

Fig. 103. Cells from a melanotic tumour of the parotid gland extirpated in 1851 by Herr Textor. A. Free cells with division of the nucleon and nuclei. B. Network of connective tissue-corpuscles with division of their nuclei. 300 diameters.

the entire structure is full of nuclei, which often attain the size of the whole original cell. Such formations occur in

Fig. 104.

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many tumours in such large quantities, that in England a particular species is thereby distinguished, and on the proposal of Paget a myeloid tumour (medullary swelling) has been received into the classification. This formation is not however confined to the medulla of the bones but occasionally occurs in nearly all situations.

Muscle, upon irritation, exhibits precisely similar forms. Whilst transversely striated muscles are generally provided with nuclei at certain intervals, though in no great abundance, we find, on examining a muscle in the neighbourhood of an irritated part, as for example, a wound, a corroded or ulcerated surface, that a multiplication of the nuclei is going on in it; we see nuclei with two nucleoli; then come constricted, and then divided, nuclei (Comp. Figs. 23, b, c; M, B, C), and so it goes on, until we find in different places whole groups of nuclei lying side by side, in which the divisions have taken place to a large extent, or else whole rows of them, one behind the other. In the most marked cases of this sort the number of nuclei increases to such a degree, that at first sight we can scarcely believe we are looking at muscles; and that fragments of the primitive fasciculi offer the greatest resemblance to those plaques a plusieurs noyaux

Fig. 104. Cells from the marrow of bones, a. Small cells with single and divided nuclei. 6, b. Large, many-nucleated cells. 350 diameters. From Kolliker, *Mikr. Anat.' I, p. 364, fig. 113.

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