Numerous experiments have been made to propagate the disease by inoculation; they have in general failed, but the skin has become red or slightly inflamed, or only pustular. Remak is stated to have inoculated successfully, after removing the cuticle and attaching the favus crust by means of strips of plaster for thirty-six or more hours. There can be no question that favus is contagious, but it is not so clear under what circumstances the contagion is received. Early life is one of the elements favourable to its development, and neglect of ordinary cleanliness is commonly assigned to be another, but this is not invariable. It is during its growth, when the crusts are first formed, that favus appears most contagious, as at this period the sporules are abundant. After a time. the crust loses its distinctive character in this respect, and the hair becomes destitute of spores. At a still later stage the scalp, supposing the hair to be cut close and recovery is proceeding, bears no small resemblance to chronic eczema, as far as external appearances are concerned.

Favus is not confined to the head, but may occupy the extremities or trunk. Although it may attack the nails, it seldom includes the hands or feet.

Favus has no necessary connexion with struma, although it cannot be denied that it is frequently found in phthisical subjects. Perhaps there may be something in the cutaneous secretion in these cases, that favors the growth of the sporules. Again, patients who have already suffered from this disease are, more than others, liable to be attacked. Whether this be due to the complaint not being wholly cured, the germ of it still remaining, I do not decide; but the fact remains, that in a severe case after apparent recovery, the patient is

very subject to experience a relapse. The loss of hair will depend upon the state of the hair follicles: when the latter are obliterated, which takes place after successive attacks, no regeneration of hair ensues; the patches remain smooth and the skin inelastic, but in the less severe forms of this disease no permanent baldness follows.

There are good grounds for the belief that favus is becoming every year more rare. At the Skin Hospital it is now seldom seen. For some excellent examples of it in this country I am indebted to the courtesy of Dr. Hillier, under whose care at the Hospital for Sick Children in London, several cases have been admitted. In Paris at St. Louis, the disease is common enough, both among the in- and out-patients. It is, however, only in the lowest classes, among the children of the very poor and wretched, that it occurs at all.

The actual seat of favus is still unsettled. According to some observers the disease commences in the hair follicle, and various are the changes which it is supposed to undergo before it reaches the surface in the form of a cup-shaped crust. By others, among whom may be mentioned Gruby and Bennett, the mycelium is received between the layers of the epidermis, a furfuraceous desquamation of the cuticle precedes the crusts, and it is from the walls of the latter that the sporules are formed. What lends weight to this theory, and to me renders its acceptance the more trustworthy, is the fact that the attached surface of the crust is coated with a layer of epidermic scales, which separate the granular mass from the cutis, and consequently from the hair follicle. The latter I believe to be affected secondarily; and when the hair is finally destroyed, the change is caused by

the pressure acting on the follicle, rather than by any primary defect in the condition of the follicle itself. Some authors, as Rayer, speak of favus as if the disease were originally pustular. This is an error. Pustules may coexist with favus, but they are quite independent of it.

Favus is often stated to emit an offensive odour, which has been compared to the urine of cats. This may happen in a very advanced stage, when the patient has suffered the complaint to run its course, to the complete exclusion of all cleanliness, but it is not a constant result; and I have seen favus involving the greater part of the trunk, face, and extremities, unattended by any disagreeable smell. When it occurs unchecked, the disease is generally complicated with vermin, which find refuge in the fissures of the crusts; and is further aggravated by pain, which the patient seeks to alleviate by violently scratching the part.

The common remedy in France is epilation, as practised Treatment. at St. Louis. This mode of treatment is generally entrusted to an experienced attendant, who is furnished with a pair of forceps, having broad and closely fitting edges. Simple as the operation may appear to be, it requires some degree of skill to perform it properly. The hairs should be extracted in the direction in which they grow, and as this complaint renders them brittle, they will be very apt to break off at their roots. The extent to which the treatment should be carried at a single sitting will depend partly on the feeling of the patient, and still more on the dexterity of the operator, but as a rule the procedure is more painful at first than afterwards. The time that it may altogether occupy before the diseased hairs are thus eradicated will be commensurate with the

extent to which the complaint has spread. The new hairs which form are distinguishable from the old by their being less brittle, and not so wanting in lustre, although still small. It is scarcely necessary to add, that before epilation can be undertaken, the surface of the scalp must be thoroughly cleansed, and the hair itself cut quite short. If after some days no signs of crusts appear, nor any remnant of the cryptogame be detected in the hair, the patient may be pronounced convalescent, but it will be as well not to lose sight of him, for the spores will sometimes lie dormant for a while. A return of the disease is shown by a slight redness, and a furfuraceous condition of the scalp. In the intervals between the extraction of the hairs, the surface should be anointed with a liniment composed of sulphur or mercury. Other plans of treatment are also in vogue abroad. Thus, after the head has been cleared of all crusts, it is washed with soap and water. This step is repeated as often as is necessary, until the scalp is thoroughly clean. The surface is then covered with an ointment, composed of one or two drachms of the bicarbonate of potash to an ounce of lard, which is applied every alternate evening for three or four weeks, according to the severity of the case. In England epilation is seldom had recourse to. After the usual preparatory process in the way of cleansing, tar or the ung. picis liquidæ, or a preparation of sulphur is used. In most instances this seems to answer every purpose. Neligan, who has had considerable experience of this disease in Ireland, prefers the iodide of lead ointment, in the proportion of half a drachm to an ounce of cerate; and states that it has succeeded so well in his hands that he has had no occasion to try any other remedy.

SCABIES, or the itch, to use a more common expression, Scabies. is a complaint variously classed by different writers, according to the preponderating character of some particular symptom, whether this consist of vesicles, papules, or pustules. Whatever sign it may present, and there is scarcely any disease of the skin which scabies may not simulate, it owes its origin and significance to an insect-the 'acarus' or 'sarcoptes hominis.'

Although known from a very remote period, as early as the time of Avenzoar in the twelfth century, it is only within the present age that the acarus has formed the subject of much accurate research. In this country Mr. Erasmus Wilson, and abroad the labours of Gras, Hebra, Gudden, and Bourguinon have left little that is wanting in completeness in whatever relates to its organization, development, and habits. For the anatomy of the creature I have to record the results of my own microscopical investigations; but, less fortunate than Bourguinon, I have not hitherto succeeded in tracing the various changes occurring in the ova, from the first appearance of the ovum to the maturity of the contained insect. For this part of my subject I am indebted to the valuable monograph of this latter writer.

The acarus has been compared, and not inaptly, to a Anatomical tortoise. It is, however, more globular than oval, and

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characters.