reason also erroneously held to be an ulcer. This is particularly liable to occur during the emaciation of the last part of life, and in the subsequent drying of the open surface; in consequence of which there is sometimes no solid base to be discovered in the examination after death.

The thickness of the solid margin and base varies, both with the conditions which favour or resist its increase, and with the rate of the succeeding ulceration. In the diploe of a bone growth exceeds destruction, and the tumour becomes a broad and thick plate of the characteristic morbid substance. The brain likewise favours the accumulation more than the ulceration of the deposit, which consequently reaches in that organ a thickness of a quarter of an inch. There is also a difference in the quantity of solid material in the early and the later years of the disease. In recent cases the margin is comparatively thin; but after a long duration, and in the decline of the general strength of the patient, the morbid edge becomes half an inch thick, and is but little firm. Again, the secondary ulcerative process in some parts follows the growth slowly, and the hard margin of the cavity attains a thickness of more than a quarter of an inch elsewhere ulceration is rapid, and nearly or completely overtakes the growth. In the latter case the appearance resembles that of an ordinary sore before the formation of granulations; its edge

becomes quite soft, and it may begin to cicatrize; but after a time solid growth arises in it anew, or advances upon it from adjoining parts of the margin, and eventually disease is re-established everywhere. The sweeping of erysipelas over the sore occasionally affords an illustration of this statement. During the activity of that disease the solid edge of the ulcer is wholly absorbed, but it is always eventually reproduced.

When ulceration thus breaks out afresh after a partial cicatrization, the situation in which it sometimes occurs is peculiar. It does not always recommence at the edge of the sore, where granulations and scar adjoin, but at the line where the scar is continuous with the skin. The result is to sever the last formed cicatrix from the skin by a new line or trench of ulceration. Though somewhat resembling a healing wound and scar dragged open by the contraction of the granulations, the appearance suggests rather that the process of ulceration is specifically associated with the remnant of solid deposit in the texture of the skin. It is an ulceration conspicuously independent of the existing ulcer, and it appears to be a repetition of the first excoriation of the original pimple.

Neither the advance of the solid growth, nor the ulceration succeeding it, occurs at a uniform rate. On the contrary the progress of the growth is very

unequal, and in the skin its edge accordingly presents a serrated appearance, from the alternately greater and less destruction of the integuments. The ragged outline produced by these ridges and intervening notches is well expressed in the title, Rodent. The notches, which correspond to the more rapid extension of the disease, are sometimes an inch further from its original centre than are adjoining portions of still undestroyed integument; and on the cheek, one part of the destructive process may be three inches in advance of that next it.

The growth of the solid disease is not limited to the integuments around the ulcerated cavity; it advances in depth as well as in superficial area, involving all the structures it encounters. It infilters the glandular textures and the bony, it spreads by the mucous and the fibrous tissues, and after perforating the skull, it will still grow into the very substance of the brain. In the succeeding ulceration these structures are likewise removed, and the excavation becomes deep as well as wide. There is here again a considerable inequality in the rate at which different textures are destroyed. No tissue yields so quickly as the skin, and the great superficial extent of the disease is thus often its chief characteristic. The eyelids sometimes are slowly destroyed by the creeping of the disease over them, long before any but catarrhal and traumatic changes occur in the exposed eyeballs. Bone

is somewhat easily invaded by the growth, in which it either becomes necrosed or is absorbed or crumbles away. Cartilages long resist the encroachment of the disease. The relative progress through different textures can be measured by the contrasts of its rate in different directions. During the extension of it in skin from a central pimple over the entire forehead, upper eyelids, and nose, the frontal bone was perforated, but no part of the tarsal or nasal cartilages became affected. In a somewhat similar case, the frontal bone was perforated, and the substance of the brain was destroyed to the depth of more than an inch, whilst the skin was being removed over an area equal to a woman's open hand. An excavation in another case reached the mastoid process in one direction, and nearly as far as the corner of the mouth in the other, without penetrating the bones of the cranium. It had during the same period almost entirely removed the pinna of the ear and the parotid gland, and had occasioned a complete paralysis of the facial muscles of the same side. Again, whilst the central parts of the surface were being destroyed between the eyebrow and the lip, and half the cheek on the right side, the entire substance of the subjacent superior maxillary bone, with the teeth and palate, was removed, and only the soft palate remained, supported by a slender bridge of the hinder portion of the palate bones. Meanwhile the

cartilages of the left side of the nose were but partly destroyed. The septa of the facial air cavities soon yield, being thin and involved in the double destruction of their mucous coverings. I have had no opportunity of noticing the comparative resistance of the bony and the cartilaginous septa.

The diseased substance is almost invariably concentrated into one mass. However far it may spread

in the tissues, and whatever gap may have been produced by intervening ulceration, there has been a continuity of its growth from the original pimple to the furthest margin of the disease. On one occasion, however, I observed an outlying nodule beneath the skin, separated from the growing margin of the original disease by a quarter of an inch of apparently healthy integument. Mr. Paget also once saw a similar isolated nodule of this disease.* The occurrence resembles that which is by no means uncommon in Cancer, in which seemingly isolated nodules of the disease spring up in the vicinity of the original tumour. Though distinct from that tumour, so far as we can perceive by grosser modes of examination, they are yet virtually continuous with it, having in all probability originated from the detachment and conveyance of minute fragments of the original tumour, or from its easier growth along some single intervening structure.

* Holmes' System of Surgery, vol. i. p. 211.