A distinction is at once apparent between the solid substance constituting the margin of the Rodent disease and the material of an equally firm Scirrhus. The latter possesses eminently the character of contractility, draws towards itself all adjoining extensile structures, and produces thereby a pitting and cupping even of its own cut or exposed surface: the Rodent substance, on the contrary, is entirely devoid of this quality. As it advances along a lip or an eyelid, it does not alter the contour or the position of the yet undestroyed segment. It will perforate the face at the junction of the cheek, upper lip, and ala of the nose, without causing any deviation of the outline of either of them. Or if half of a lip or an eye-lid have been removed, the remaining portion, bordered by the solid deposit and the ulcer, hangs in its natural position. The ulcerated cavity thus measures precisely the extent of the destruction of the natural parts. No contraction of the soft tissues takes place except as a result of cicatrization, between which process and the inelastic state of the Rodent disease there is a very great contrast, which is most remarkable in the lessening of the disfiguring cavity during healing after an operation. Between Epithelial Cancers of the skin and the Rodent Cancers there is little, if any, difference in respect to the contractility of their solid growth, the former disease possessing very little of this quality in whatever part of the surface it occurs.

The microscopic characters of the solid infiltrating substance, which constitutes the disease, are not precisely those of any natural texture; yet they do not ordinarily so much deviate from the appearances of cutaneous epithelium and of granulations, as to be entitled to the epithet, malignant. In some respects, however, the descriptions of the microscopic characters of Rodent disease, which are to be read in published works, differ from those which I have observed. I have found parts of the diseased substance, presenting a minute textural composition, precisely answering to that of the epithelial form of Cancer. A portion of the solid substance taken from the interior of the frontal bone showed just such appearances as the ordinary Cancer of the lower lip; epithelial cells, brood cells like the section of an onion, many fragments of cells and nuclei, very distinct, round, dark, granular cells, and oil. An equal resemblance to epithelial Cancer was noticed by my colleague, Mr. Hulke, in the microscopic examination of fragments which I removed with the globe of the eye in one of the cases, detailed in the Appendix. As it sometimes shows itself in skin, the disease is made up of such innocent microscopic corpuscles that it has been likened to a chronic ulcer of the leg, and to a perforating ulcer of the stomach. But, even if it were satisfactory to decide the innocency of a disease by its microscopic, apart from its clinical characters, that

decision is no longer conclusive, in the case of Rodent disease. It is never spontaneously curable, and not always microscopically innocent.

The foregoing paragraph contains the results of my own observations of this disease, but since writing it I have met with a remark by M. Lebert which, in conjunction with my own observations, suggests a new consideration. It appears not improbable that the nature of the morbid process may differ at different parts of the disease. His remarks are in the following paragraph.

'Although a rodent ulcer is the most common termination of cancroid of the face, it nevertheless most frequently begins with a little pimple, like a wart, the structure of which exactly resembles that of the lip. Its epidermal surface is soon shed and ulceration established, and then, especially in the malar and suborbital regions, can be very well perceived the papillary structure of these vegetations, which precede a deeper ulceration. And here we have to call attention to a very remarkable fact, for which we should have some difficulty in accounting; it is the structure of these papillæ in the inferior palpebral region. The epithelium which formed their circumference, or greater part, was elongated and narrow, and much resembled fibro-plastic fusiform elements. In the malar region we have found more resemblance to cancroid of the lower lip, whilst on the nose we

have scarcely ever met with these fungous excrescences formed by the papillæ. The base of these ulcers was smooth and compact, and their surface presented no elements but those of suppuration mingled with a little epidermis.'*

This remarkable observation of M. Lebert corresponds with that made by myself, that the portion of a Rodent disease occupying the interior of the frontal bone presented distinct microscopic characteristics of epithelial Cancer, which, though not always absent, are not usual in the more superficial parts. Taken together, they appear to show that the disease deviates from health in different degrees at its several parts. At its commencement in the first pimple, the minute structure is identical with that of the epithelial Cancer of the lower lip. Portions of the advancing growth retain that character, whilst the larger part loses it. Yet, as this part also, in its ceaseless growth and ulceration, arrives at certain situations or in convenient textures, the microscopic appearances of the epithelial Cancer are resumed. The influence of natural texture is probably represented in the production of the entire morbid result; and this inference seems borne out by some of the phenomena of ordinary Cancer; as where, for a time, in an open scirrhus, cicatrization advances over masses of morbid cells; or, where, in the early extension of Cancer

* Lebert, Traité Pratique, 1851, p. 658.

along the skin, non-nucleated cells are found filling the meshes of the cutaneous fibrous texture, though afterwards the microscopic elements would be like those of the advancing primary tumour.

Rodent Cancer is perhaps not quite the tardiest of the Cancers in destroying life, but it is always a disease of long duration. Its entire course usually occupies not less than five years, and it may extend beyond twenty years. The duration, in some degree, varies with its place. It lasts long on the face, where no vital organ is within its reach; but in the forehead, temple, and neck, there is danger of earlier death, on account of the proximity of the brain and the vessels. The moderate exhaustion which this disease sometimes occasions is well shown in one of the cases of M. Lebert. A poor woman at Bex, in the Canton de Vaud, had a cancroid ulcer,' which, in ten years, had excavated the nose and cheeks both widely and deeply, but had not, in that time, altered her general health, or caused emaciation, or prevented her reaching the age of 99 years. When the ulcerated surface is very large, the long-continued suppuration is apt to be exhausting, and when such an ulcer is situated over some considerable portion of the skull, it may be expected that so enormous an issue would produce some injurious influence on the brain. I have watched for symptoms of this kind from the presence of a vast ulcer discharging some

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