Pityriaais vereicolor was long a puzzle, because it has certainly something of a squamous character, but in a very subordinate degree. Its chief mark is a yellowish-brown discoloration, in small circular patches, which sometimes spread all over the body. There is no vesication, no crust ; the small scales of the epidermis fall in larger quantity than in health, producing some degree of roughness; and the eruption is sometimes attended with much itching. It is now shown to be connected with the growth of a fungus. The varieties called rubra and nigra probably belong to the same category : they are described as being very rare, and none have come under my own observation.
§ 8. Tubercle of the not a very common malady, it is necessary to point out how it may be distinguished from other cutaneous affections to which it bears some resem blance. It is most frequently seen on the face, and is sometimes limited to the nose or the ear, producing a most disagreeable alteration of the features. The disease consists of smooth, rounded eminences, which are accompanied by a general puffiness of the adjacent skin, and marked by livid or bronze discoloration. The name is an unfortunate one, because it is usually applied to one particular development of the strumous diathesis, with which tubercles of the skin have nothing in common. Usually aggre gated over a limited surface, the eruption does not present any regular groups, except in those rare forms which have received the names of frambcesia and molluecum, from fancied resemblances which they present. In very severe cases it may implicate large tracts of skin, and then the name " Elephantiasis of the Greeks" is applied to it : " Elephantiasis of the Arabians" is a wholly different disease: French authors employ this name even in mild cases. It is always accompanied by disorder of the assimilating functions, and common belief assigns as its frequent cause the improper use of stimulants.
In speaking of acne it was mentioned that at one stage of its progress, when no suppuration was going on, and the skin presented a red and rugged appearance, it was liable to be confounded with tubercle. Such a mistake is very liable to be made by one who knows skin diseases only as described in books, because both are equally found in persons of dissipated habits. Very little experience serves to distinguish the smaller size and brighter color of the hardened points in acne from the rounded knobs and livid color of tuber cles : the disagreeable expression produced by the tumid features of the latter are very different from the bloated aspect of the drunkard whose nose and cheeks are inflamed by an eruption of acne. In addition to this, the history,
if rightly inquired into, details the existence of previous suppuration in the one and its absence in the other.
Tubercle of the skin is one of those cutaneous affections which have a counterpart among the syphilitic eruptions : its diagnosis, however, is, as we shall find, not difficult.
§ 9. Syphilitic Eruptions.—This class of eruptions has no legi timate place among cutaneous disorders ; they are the mere ex ponents of a specific disease ; but it is necessary in a work on diagnosis to point out their resemblance to some of those which have been already enumerated, and to show how they may be distinguished from them.
Their most marked feature is the copper-colored tint of the surrounding skin ; but this is only another instance in which. persons who trust to one sign, however uniform, are sure to be occasionally mistaken. Not only do eruptions, which are cer tainly not syphilitic, sometimes present a discoloration in healing which can be called by no other name, but true syphilitic erup,. tions are occasionally free from it. It is only by studying the whole history of the affection that a correct opinion can be formed. The first question is whether the characters of the eruptions cor respond exactly to those belonging to any of the classes of disease already enumerated, bee,ause an individual may have had primary syphilis, and the system may still not have become infected. If it present any peculiarities, and especially if marked by the coppery tint, the next point is to inquire into the possibility of syphilitic contagion; and this can only be done, especially with females, by indirect interrogation : it is still more important to ascertain whether there have been any symptoms of syphilitic poison, such as sore throat or periosteal inflammation: the cir cumstance of the hair fallbag ofg or the existence of iritis, tends to the same conclusion.
In regard to the eruption itself, we notice that the copper color is not limited to parts which are already healed, except perhaps in urticaria ; and the disorder does not exactly correspond to any of the definitions already given : it approaches nearer to one than another, and may simulate any of them except the vesicular, which, if it ever exist, is extremely rare.