1847]

Wilson on Diseases of the Skin.

209

ON DISEASES OF THE SKIN. By Erasmus Wilson, F.R.S., Consulting Surgeon to the St. Pancras Infirmary, Lecturer on Anatomy and Physiology in the Middlesex Hospital, &c. Second Edition, with coloured Plates, 8vo, pp. 482. London: Churchill, 1847.

THREE years have scarcely elapsed since we had occasion to speak of this work in terms of commendation, and we are rejoiced to find that the opinion which we then gave of its merits has been participated in by the profession, for whom it was written. The first edition has now been many months out of print, and the present volume, with copious additions, and eight beautifully executed illustrations, is intended to supply its place. The rapid sale of the first edition has shown that the subject is one of much interest to the profession, and it proves also that the author has accomplished his task ably and satisfactorily. In truth, "THE DISEASES OF THE SKIN," by Mr. Erasmus Wilson, may now be regarded as the standard work in that department of medical literature. The plates by which this edition is accompanied leave nothing to be desired, so far as excellence of delineation and perfect accuracy of illustration are concerned. They are drawn and coloured after nature, and are engraved on steel by Adlard, with a view to giving full effect to the peculiar tints of colour of these diseases. As an explanation of the nature and objects of the plates, we cannot do better than quote the author's words, and express our conviction that they completely fulfil his intentions.

"The present edition has the advantage over its predecessor of being illustrated with coloured delineations drawn from nature, and engraved on steel. The plates are eight in number, each representing a group of diseases. For example, if the reader wish to place before his eyes the group of congestive diseases' of the derma, he may turn to Plate 1, where he will find displayed, Urticaria, Roseola, and Erythema; Erysipelas being omitted, partly because its illustration is less necessary than that of other cutaneous diseases, and partly on account of the large extent of surface its delineation would require. If the reader would contrast the congestive group' of cutaneous discases with others, he will find in Plate 2, the asthenic effusive group,' namely, Pemphigus and Rupia; in Plate 3, the sthenic effusive group, namely, Herpes and Eczema ; in Plate 4, the pustular group,' Impetigo and Ecthyma; in Plate 5, the 'papular group,' Lichen, Strophulus, and Prurigo; in Plate 6, the squamous group,' Lepra, Psoriasis, and Pityriasis; Plate 7 illustrates the peculiar morbid alteration of the skin termed Lupus non exedens; and Plate 8, certain diseases of the hair-follicles and hairs, namely, Acne, Sycosis, Favus, and Trichosis furfuracea. "Another feature in the Plates which accompany this volume, and one at which I have especially aimed, is that of bringing together as many of the varieties of a given disease as possible. My reasons are twofold-firstly, that the leading characters of these varieties may be the more easily comprehended and contrasted; and, secondly, that the reader may be placed in possession of the largest amount of illustration admitting of being compressed into a limited space. For example, in the upper division of Plate 1 will be found four varieties of Urticaria, four varieties of Roseola, and, in the lower, six varieties of Erythema; making in the single plate fourteen specimens of cutaneous disease, the separate figures not being in any way stinted in dimensions, but being, in reality, of the

NEW SERIES, NO. IX.-V.

P

size of life. With the most ample space at my command, I could have done little more than this. I might have repeated forms, but the matter to be impressed on the mind could not have been rendered more clear or more precise. Plate 2 represents, in the upper division, two varieties of Pemphigus; and, in the lower, three varieties of Rupia. The upper division of Plate 3 exhibits four varieties of Herpes, and the lower, the same number of varieties of Eczema. In Plate 4, the number of varieties of Impetigo, in the upper division, is four; and in the lower division, the varieties of Ecthyma are three. In Plate 5, there are, in the upper division, six varieties of Lichen; and in the lower, four varieties of Strophulus, and one of Prurigo. Plate 6 contains, in the upper division, three varieties of Lepra; and in the lower, three varieties of Psoriasis, and one of Pityriasis. Plate 7 is devoted to the single subject of Lupus non exedens; while in Plate 8 are four varieties of Acne, one of Sycosis, two of Favus, and one of Trichosis. So that, in the limited compass of eight octavo plates, no less than sixty-one subjects are represented." P. x.

In the present edition, Mr. Wilson has added very considerably to our stock of knowledge on the structure of the skin, the foundation upon which all our notions of pathology and all our practical applications must be based. Conceiving," he observes, "that no real improvement could be made in the practical department of the subject in any other way than through the advancement of the scientific portion of these diseases, I have continued to bestow much attention and labour on the examination of the cutaneous tissues." In furtherance of this purpose, the author has introduced into the preliminary chapter on the Anatomy and Physiology of the Skin, his original researches on the structure of the epiderma, the hair, and several of the morbid tissues. The following is Mr. Wilson's description of the structure of a hair.

"In structure a hair is composed of three different tissues, namely, of a loose cellulated tissue which occupies its centre, and constitutes the medulla or pith; a fibrous tissue which incloses the preceding and forms the chief bulk of human hair; and a thin layer of superimposed scales which envelopes the fibrous structure, and forms the smooth, external surface of the hair.

"The medulla is absent in the minute or downy hairs, and is not unfrequently absent or small in quantity in fine hairs, from whatever region they are selected. In the coarser hairs of the head and of the body, on the other hand, it is always present, and it is especially remarkable in grey hair. It varies in breadth from a mere line to a cylindrical body of one-third the diameter of the hair, and is composed of large nucleated cells of a globular or oval figure filled with granules and packed together, apparently without order. When newly formed, these cells with their granules are distended with fluid, but in the shaft of the hair the cells frequently contain air, which from its highly refractive powers, gives the medulla a dark appearance when examined with the microscope. Varieties in structure of the hair are very unusual: I have, however, once observed the presence of two medulla; the displacement of the medulla nearer to one side of the periphery of the hair than to the other in the short and thick hairs of the body is

not so uncommon.

"The middle or fibrous layer of the hair is composed of oval-shaped cells closely packed together, and arranged in a linear order. These cells are identical in structure with the cells of the deep stratum of the epiderma, that is to say, they are composed of granules congregated around a central granule which constitutes the nucleus of the cell. When examined with the microscope it is not in all cases easy to discover the cells, but their component granules are always obvious, and from the plan of disposition of the cells, and their oblong shape, the granules have a linear arrangement, and assume the appearance of

1847]

Structural Anatomy of Hair.

211

fibres. The hair-fibres offer some variety of appearance according to the focus in which they are viewed. For exa:ople, with a superficial focus the peripheral granules are alone seen, and the hair appears to be entirely composed of granules arranged in single rows. With a deeper focus the rows of granules appear to be associated in pairs, each pair having between them an unconnected row of dark and apparently nuclear granules. In this view the fibres resemble, very closely, a chain composed of open links. While with a still deeper focus, the centre of the cell, with its nucleus and granular periphery, is brought into view. In different hairs, these three appearances are seen with various degrees of distinctness.

"The colour of hair appears to reside partly in the granules, and partly in an intergranular pigmentary substance which occupies the interstices of the granules and of the fibres. The most deeply coloured granules are those which constitute the nuclei of the cells, and in the lighter hairs these alone give colour to the fibrous structure. In the darker hairs more or less of the peripheral granules are also coloured, and pigment may be observed in greater or less abundance in the interfibrous spaces. With respect to the granules the pigment appears to occupy their periphery, sometimes surrounding them completely, and sometimes occupying a portion only of their surface. In the peripheral granules of the cells the outer segment is the more frequent seat of the pigment, while many are entirely destitute of that production. This total absence of colour in many of the granules composing even the blackest hair, gives to the fibrous structure, when examined with the microscope, an interruptedly streaked appearance, and the irregular intermixture of pigment granules with colourless granules, bestows upon the tissue between the streaks a dotted character. In red hair, the granules have a delicate golden yellow tint, while the pigmentary matter is amber coloured. In the white hair of Albinoes and of the aged, the pigment is entirely wanting.

"The external layer of a hair is a thin and transparent envelope, measuring in the hairs of the head about of an inch in diameter. It is composed of flattened scales similar to those of the epiderma, and the scales forming the surface of the layer overlap each other from the root to the point of the hair. The overlapping border of the scale is notched and convex, and forms a slight projection beyond the level of the surface. Seen with the microscope, the prominent edges of the scales have the appearance of undulating and jagged lines, which cross at right angles the shaft of the hair. The prominence of the edges of the superficial scales of a hair is the cause of the sensation of roughness which we experience in drawing a hair between the fingers from the point towards the root, a sensation which is not perceived when the direction of the hair is reversed. It explains also, the circumstance of hairs occasionally working their way into wounds, beneath the nails, and into the gums. In the hairs of the axilla the external layer is generally more or less split up into fibres, which give it a shaggy appearance. Sometimes this appearance occurs only on one side of the hair, or more on one side than the other, while at others it is equally conspicuous around the entire shaft. It forms a remarkable distinctive character of the hairs of this region, and is due, as I believe, not to original formation, but to their saturation with the perspiratory fluid." P. 25.

Again, in reference to the follicle of the hair, and the mode of implantation of the latter within the skin, he observes :

"The follicle of the hair is a tubular canal excavated in the substance of the derma and lined by a thick layer of epiderma. It consequently presents the same three structures that enter into the composition of the skin, namely, an epidermal lining or sheath, a vascular layer, and the common fibrous tissue of the corium. Of the latter it is unnecessary to say more than that it offers the same characters around the hair as upon the surface of the derma, and that it

* P

sends a delicate sheath downwards upon the root of the hair when the latter extends into the subcutaneous areolar tissue. The vascular layer corresponds with the papillary layer of the derma, and supports a fine net-work of capillary vessels, which supply nutrition to the epidermal sheath and hair. The epidermal layer is composed of strata of superimposed cells, identical in structure with those of the epiderma. It is nearly as thick, and often thicker than the hair which it incloses, and lies in close contact with the latter, and, at its lower part it terminates in a slightly expanded and cellular mass, the pulp of the hair.

"The hair-follicle terminates inferiorly in a slightly dilated cœcal pouch, which is filled for about the extent of ro of an inch, with a mass of minute granules and cells. This mass of granules and cells is the pulp of the hair, and the cells are progressively converted into the substance of the hair. The cells produced at the middle of the fundus of the cœcal pouch necessarily proceed upwards in a direct line and are the first converted into fibres, hence the pointed character of a hair torn up from its root. The cells from the sides of the pouch proceed, with a gentle curve upwards and inwards, and merge into the substance of the root of the hair, and those from the upper part of the pulp assume an almost vertical position, and constitute, on the one hand, the outer layer of the hair, and on the other, the epiderma of the follicle. So that, at its upper part, the hairpulp may be said to divide into two parts, a central and isolated part which constitutes the shaft of the hair, and a tubular sheath which remains in connexion with the vascular part of the follicle on the one hand, and is in apposition with the surface of the hair on the other. The structure of the pulp and the mode of growth of the hair remind us forcibly of the formation and growth of the teeth, and furnish an additional reason for regarding the latter as dermal appendages. They explain also the well-known fact that, if the epiderma be withdrawn from the derma when loosened by decomposition, the hairs may frequently be removed inclosed in their epidermal sheaths, which obviously extend uninjured around the bulb, and isolate the hair from the vascular part of the skin. I have found the vibrissæ nasi the best fitted for illustrating this point, and I may remark that the proof of such an organization completely sets at rest the question of the vascularity of the bulb." P. 27.

Among the subjects contained in this edition which have been retouched by the author, we observe the following in reference to the pathological nature of the papular diseases.

"In the preceding edition of this work, I stated my belief that the precise element of the dermal system affected in the papular diseases was the papillæ of the skin. More recent and careful examinations have proved to me that this is not the case, but that the real seat of morbid change is the vascular boundary of the various excretory tubules of the skin: for example, the sudoriferous and sebiferous ducts and hair-follicles. This fact being determined, we have an explanation of various of the phenomena which accompany the eruption: for example, the frequent perforation of the pimples by a hair, the formation of a thin scale upon the summit of the papula, the occasional appearance of a minute aperture in this situation, and the oozing of a transparent and colourless fluid from the same point. We can also better understand the provoking itching which is a symptom of the eruption, the obstruction which is offered to the escape of secretions, and the obstinacy of these disorders. The papulæ of prurigo are perfectly identical with the papulæ of lichen, the difference between them being, that the latter are generally acute in their course, while the former are always chronic. But there is an appearance of the skin in prurigo that must be familiar to all who are conversant with cutaneous diseases; an unevenness of surface, produced by numberless slight but broad elevations, separated from each other by the linear markings of the skin. Now these are the elevations which have been described by all dermatologists, not excluding myself, under the name

1847]

Pathology of Lichen and Prurigo.

213

of the broad and flat papula of prurigo. Soft and smooth papulæ, somewhat larger and less acuminated than those of lichen, and seldom appearing red or inflamed, except from violent friction. Hence an inattentive observer may overlook the papulæ altogether.' Rayer speaks of them as being soft to the touch, and broader than those of lichen, from which they also differ in preserving the natural colour of the skin.' "They occasionally project in so slight a degree, that they appear to be situated rather in the substance than on the surface of the skin.' Now there is an evident obscurity about these descriptions, a contradiction in fact, which must have involved many in perplexity with regard to the real meaning of the authors. Papulæ, precisely defined, broad, soft, smooth and large, and yet, not distinguishable in colour from the adjacent skin, easily overlooked, and suggesting to the practised eye some uncertainty as to whether they were in or upon the skin. I will endeavour to explain the mystery.

"Prurigo, I believe to be, in its origin, a disease of the nervous system, and specially, of the cutaneous nerves. As a consequence of the altered innervation of the skin, the dermal tissues become changed in structure-namely, condensed and thickened. The most careless examination is sufficient to establish these two points; the skin feels hard, it moves like a piece of thick leather; the area included between the lines of motion are large; its natural suppleness is gone; its very colour is changed; it looks yellowish and dirty. But it is smooth; there are no such projections as we should call pimples, or if there be, they are few and scattered. Arrived at this point, there remains but one conclusion for the student. There are no papulæ, therefore the disorder cannot be prurigo. And yet the disease is so characteristically prurigo, that, setting aside the symptom of pruritus, the dermatologist is able to decide at once upon its name.

"What then, are the signs by which prurigo is so immediately distinguished? They are, the thickening and condensation of the skin, and the consequences of this condition. Upon close examination, the angular area included by the linear markings of the skin, are seen to be elevated above their natural level, the elevation being occasioned by the thickening of the derma. That this is the case is evident from the position of the pores-namely, in the furrows which constitute the linear markings, and at the point of divergence of several of these. The elevations, therefore, are simply the effect of a swollen state of the derma, the area being magnified by hypertrophy, and the linear markings being magnified in depth by the same cause. These swollen area are the so-called papulæ, the broad and flat and smooth papulæ. It is not, then, to be wondered at, that they should be with difficulty discerned, that they should be overlooked,' seeing, as I have shown, that they are not papulæ at all.

"But we do meet with papulæ in prurigo, although not a necessary feature of that disease. These papulæ are not the area of the linear markings of the skin; they occupy the grooves of the linear markings. They are, in fact, the pores raised into pimples, and are identical with the pimples of lichen. It is these latter which generally suffer abrasion of their tips from scratching, and then become surmounted by a small dark-coloured scab." P. 239.

The Chapter on the tuberculous affections of the skin, including the two forms of lupus, namely, non-exedens and exedens, is entirely new. Mr. Wilson is of opinion that the diseases severally denominated" Vitiligo" and "Leuce" are in reality one and the same morbid affection, and that they correspond in every particular with lupus non-exedens. The treatment from which he has obtained the best results in the cutaneous variety of lupus, is a prolonged course of the liquor hydriodatis hydrargyri et arsenici, at the same time modifying the local disease by the occasional application of acetum cantharidis.

Mr. Wilson's classification, which is essentially physiological and practical, we gave in full in our review of the first edition of this work. In