What is anaesthesia?

Anaesthesia is a diminution, comparative or complete, of cutaneous sensibility. It is usually localized, and is met with in the course of certain nervous affections. It is also encountered in leprosy, morph[oe]a and like diseases.

Pruritus.

What do you understand by pruritus?

Pruritus is a functional disease of the skin, the sole symptom of which is itching, there being no structural change.

Describe the symptoms of pruritus.

The sole and essential symptom is itchiness, usually more or less paroxysmal, and worse at night. There are no primary structural lesions, but in severe and persistent cases the parts become so irritated by continued scratching that secondary lesions, such as papules and slight thickening and infiltration, may result. It is much more common in advanced life--_pruritus senilis_. In such cases, as well as in those cases in younger and middle-aged individuals in which the itchiness develops at the approach of cold weather and disappears upon the coming of the warm season (_pruritus hiemalis_), the pruritus is usually more or less generalized, although not infrequently in the latter the legs are specially involved.

In some individuals an attack of pruritus, of variable intensity, lasting from five to thirty minutes, comes on immediately after a bath (_bath-pruritus_). It is usually confined to the legs from the hips down.

Is pruritus always more or less generalized?

No; not infrequently the itching is limited to the genital region (_pruritus scroti_, _pruritus v.u.l.v.ae_) or to the a.n.u.s (_pruritus ani_).

To what may pruritus often be ascribed?

To digestive and intestinal derangements, hepatic disorders, the uric acid diathesis, gestation, diabetes mellitus, and a depraved state of the nervous system.

Pruritus v.u.l.v.ae is at times due to irritating discharges, and pruritus ani occasionally to hemorrhoids and seat-worms.

Is there any difficulty in the diagnosis of pruritus?

No. The subjective symptom of itching without the presence of structural lesions is diagnostic. In those severe and persistent cases in which excoriations and papules have resulted from the scratching, the history of the case, together with its course, must be considered. Care should be taken not to confound it with pediculosis. In this latter the excoriations usually have a somewhat peculiar distribution, being most abundant on those parts of the body with which the clothing lies closely in contact. (See Pediculosis corporis.)

In pruritus of the genitocrural region the possibility of pediculi being the cause must be kept in mind; an examination of the parts for the parasite or for ova (attached to the hairs) would prevent error. (See Pediculosis pubis.)

What prognosis would you give in pruritus?

In the majority of cases the condition responds to proper treatment, but in others it proves rebellious. The prognosis depends, in fact, upon the removability of the cause. Temporary relief may always be given by external applications.

How would you treat pruritus?

With systemic remedies directed toward a removal or modification of the etiological factors, and, for the temporary relief of the itching, suitable antipruritic applications. In obscure cases, quinia, salophen, lithia salts, calcium chloride, belladonna, nux vomica, a.r.s.enic, pilocarpine, and general galvanization may be variously tried. Alkalies prove useful in many cases.

Exceptionally, the relief furnished by external treatment is more or less permanent.

Name the important antipruritic applications.

Alkaline baths; lotions of carbolic acid ([dram]j-[dram]iij to Oj), of resorcin ([dram]j-[dram]iv to Oj), of liquor carbonis detergens ([Oz]j-[Oz]iv to Oj), and liquor picis alkalinus ([dram]j-[dram]iv to Oj), used cautiously. One or several ounces of alcohol and one or two drachms of glycerin in each pint of these lotions will often be of advantage, as the following:--

[Rx] Ac. carbolici, ....................... [dram]j-[dram]iij Gylcerinae, ........................... f[dram]ij Alcoholis, ........................... f[oz]ij Aquae, ......... q.s. ad .............. Oj. M.

Various dusting-powders, alone or in conjunction with the lotions.

And in some cases, especially those in which the skin is unnaturally dry, ointments may be used, such as equal parts of lard, lanolin, and petrolatum, to the ounce of which may be added from five to thirty grains of carbolic acid, three to twenty grains of thymol, ten to thirty minims of chloroform, or two to ten grains of menthol.

What external applications are to be used in the local varieties of pruritus?

In _pruritus ani_ and _pruritus v.u.l.v.ae_, in addition to the various applications above, a cocaine ointment, one to ten grains to the ounce, a strong solution of the same (gr. v-xx to [Oz]j), and an ointment containing ten to thirty minims of the oil of peppermint to the ounce; sponging with hot water, often affords temporary relief.

In pruritus v.u.l.v.ae, moreover, astringent applications and injections of zinc sulphate, alum, tannic or acetic acid, in the strength commonly employed for v.a.g.i.n.al injections, are at times curative.

In bath-pruritus weak glycerine lotions, and an ointment containing a few grains of thymol and menthol to the ounce sometimes give moderate relief. Turkish baths are sometimes free from subsequent pruritus.

CLa.s.s VIII.--PARASITIC AFFECTIONS.

Tinea Favosa.

(_Synonym:_ Favus.)

What is tinea favosa?

Tinea favosa, or favus, is a contagious vegetable-parasitic disease of the skin, characterized by pin-head to pea-sized, friable, umbilicated, cup-shaped yellow crusts, each usually perforated by a hair.

Upon what parts and at what age is favus observed?

It is usually met with upon the scalp, but it may occur upon any part of the integument. Occasionally the nails are invaded. It is seen at all ages, but is much more common in children.

Describe the symptoms of favus of the scalp.

The disease begins as a superficial inflammation or hyperaemic spot, more or less circ.u.mscribed, slightly scaly, and which is soon followed by the formation of yellowish points about the hair follicles, surrounding the hair shaft. These yellowish points or crusts increase in size, become usually as large as small peas, are cup-shaped, with the convex side pressing down upon the papillary layer, and the concave side raised several lines above the level of the skin; they are umbilicated, friable, sulphur-colored, and usually each cup or disc is perforated by a hair. Upon removal or detachment, the underlying surface is found to be somewhat excavated, reddened, atrophied and sometimes suppurating. As the disease progresses the crusting becomes more or less confluent, forming irregular ma.s.ses of thick, yellowish, mortar-like crusts or acc.u.mulations, having a peculiar, characteristic odor--that of mice, or stale, damp straw. The hairs are involved early in the disease, become brittle, l.u.s.treless, break off and fall out. In some instances, especially near the border of the crusts, are seen pustules or suppurating points. _Atrophy_ and more or less actual _scarring_ are sooner or later noted.

Itching, variable as to degree, is usually present.

What is the course of favus of the scalp?