MELANOMA.
Melanie cell-pigment, as described in a pre vious page (p. 116), may be deposited in the substance of various Adventitious Formations, —of Deposits (e. g. Tubercle), of Growths (e. g. Cancer), and of Pseudo-Tissues (e. g. Os siform structure). Growths, more or less deeply tinged by its presence, have been distinguished as a special class of products under the title of Melanotic Tumours or INIelanomata. Whe ther they have any real claim to such distinc tion will be best argued, when we have, in as few words as possible, glanced at the struc tural characters of Tumours of black colour.
These tumours are, in some instances, sar comatous, in others composed mainly of en larged vessels, in others cystornatous, in others fibrous,— the pigment being deposited be tween or within the convoluted fibres or ves sels of the mass. But no growth contains melanic pigment so frequently as cancer. Studded in points through the cancerous masses, accumulated in lumps or equably in filtrated through their substance, the cell pigment gives them a peculiar dark colour. This discolouration is by far the most common in the encephaloid species, and occurs most frequently in cancer of the eye, skin, and liver, but is not peculiar to any locality.* Misled by the frequency of this discoloura tion of cancerous tumours, various writers have endeavoured to rank " Melanosis" generally as a ,cancerous disease. Lorinser, Laennec, Dupuytren, Alibert, Meckel, vonWalther, and Cruveilhier, for instance, take this view of its nature ; and more recently Miiller has de scribed " carcinoma melanodes" as one of his six species of cancer, holding as distinct and individualized a place in the class Ence phaloid or Scirrhus. The following reasons lead us to dissent altogether from these doc trines. (1.) That melanic pigment should in itself constitute cancer is an impossibility ; it never even forms a stroma, as the cells con tinue permanently free. (2.) The stroma of many melanic tumours (as of those above referred to, fibrous, &c.) is perfectly. distinct in its physical and chemical characters from all cancerous stromata. (3.) The microsco pical characters of the pigment-cells and gra nules are the sarne in tumours of cancerous nature and in non-cancerous growths. (4.) Melanie tumours, when free from acknow ledged cancerous elements, cause no special, local, or general symptoms. (5.) When me
lanic tumours give rise to the symptoms of cancerous disease, their solid stroma is found ' to be composed in whole or in part of ence phaloid, scirrhus, or colloid. (6.) Neither the local nor general symptoms of cancers are modified by the presence of cell-pigment within them. (7.) " Melanotic tumours" are rarely solitary, it is urged by Cruveilhier; but this simply depends on the fact of ence phaloid cancer being the growth most fre quently impregnated with black pigment.
The stromata above referred to are the only kinds which we have ourselves seen or known of as elements of black coloured tumours in the human subject. But in the horse a species of melanic mass of different constitution is frequently met with ; and may, for aught we know to the contrary, occur (if so, probably only in rare instances,) in the human subject.
l'hese masses are of lobulated form, per fectly and deeply black in colour, sometimes attain great bulk, and feel remarkably elastic and spongy. Of the numerous specimens of the kind in University College Museum, an attempt has beeu made to inject one with a white material ; a few spots of white colour in the substance of the tumour alone give evi dence of' the attempt ; no trace of vascular arrangement is perceptible. A portion of the mass having been allowed to macerate in chlorine water for four days, the colour was rendered sufficiently faint for observation of the stroma. It consisted of delicate fibrils (gelatinizing with acetic acid) arranged parallel to each other, without the least appearance of meshes. The pigment-granules, which were not contained within cells, (at least, no cells were visible), lay upon the surface of the fibres in some' places, so as on first sight to give an appearance of cross lines ; in others they lay between the fibres, The conviction arises that this tumour may have been a hxmatoma; absolute proof is, we admit, yet wanting: if we are right, it would follow that the only doubtful kind of black tumour we have seen, possesses in reality, like all others, a strorna of ascertained nature, with black pigment added. And the observation lends indirect support to the view (still unesta blished) of those who presume black pigment to be, under all circumstances, formed from the colouring matter of the blood.