2. Where, on the other hand, the heterologous formation is developed and increases from an interstitial point, or even from an originally circumscribed infiltration, so that at its circumference it rather displaces than involves or embraces the elements of the affected organ, and so that its periphery becomes more or less sharply defined, it forms an individual independent heterologous mass, termed a tumor.

The distinctive characters of the two are, however, by no means strongly marked. Akin to the above division is another, almost essential to the medical practitioner, however little tenable in a scientific point of view, namely, into benign and malignant new growths (benign and malignant tumors). The connection between the two classifications consists in this, that, with certain exceptions, homoeoplasioe appear to and actually do answer to the character of benign, whilst a grade of malignancy may be predicated of a new growth proportionate to the degree of its heterogeneous nature. In this classification it is essential to determine,

1. What constitutes a benign, what a malignant new growth? 2. What are the distinctive marks of the one and the other?

In the first place, we would signify by malignant new growths, those the origin and continuance of which either are essentially bound up with, or else eventually lead to, a definite constitutional dyscrasis, a general disease giving rise to a peculiar impairment of nutrition, and a multiplication of specific new growths. No new formation is, therefore, in itself malignant, but becomes so either through a specific, pre-existent, and predetermining, or through a consecutive, general dyscrasial affection. This is perhaps the proper explanation of a malignant new growth. It does not preclude that occasional purely local relation of a malignant formation upon which the cure of the latter, spontaneous or artificial, often depends. It will be seen that whatever else is adduced as an attribute of malignant tumors ceases to be distinctive.

(a.) It is very difficult to recognize a constitutional disease as a definite one reflected in a new growth, and to discriminate between this and a cachexia engendered by the luxuriation and ichorous vent of a new growth essentially local, and pronounced benign. Besides, the constitutional affection may as yet be altogether wanting. Even where several growths coexist of the same character, or rapidly succeed each other, they need not necessarily be based upon any general dyscrasis. They may be simply so many mere local occurrences.

Certain other characteristics are indispensable for a diagnosis, and, at the same time, difficult to establish: for example, that -

(b.) Benign growths are curable by extirpation, whilst the malignant recur at the same spot, or at other spots, or even at both.

In opposition to this, it is to be urged, that many benignant new growths recur after extirpation, where the disposition to them remains, whilst, under certain conditions, many a malignant new growth does not recur, but enters upon a spontaneous process of retrogression, and becomes extinct.

(c.) Malignant new growths have a marked tendency to draw within their formative range - to convert to their own similitude - contiguous and neighboring textures.

It is to be observed, on the other hand, first, that the most malignant growths thrive and flourish as independent tumors upon a new-formed vascular apparatus of their own, without otherwise molesting the surrounding textures than by forcing them from their positions; secondly, that where the original normal textures merge in the heterologous growth, this is brought about in the malignant, precisely as it is in the benignant ones - namely, by a conversion in the sense before adverted to; that is, through reduction, disintegration, and resorption of the normal textural elements.

(d.) When malignant growths have attained their highest point of development, they break up and enter upon a process of softening, which implicates or involves surrounding and included textures, and thus serves to exhaust the organism.

In connection with this process, the following subjects for consideration suggest themselves: namely,

1st. This so-called stage of metamorphosis - this breaking up very frequently fails to occur, even in the most malignant new growths.

2d. That apart from the general difficulty of establishing the epoch of the highest development of a new formation, the act of breaking up should seem a fortunate event as regards the growth itself, which, by virtue of the elementary transformations thereby engendered, becomes deprived of its importance, and in many instances is excreted from the body.

3d. That this metamorphosis for the most part simply implies inflammation terminating in ichorous degeneration, and death of the new growth. 4th. That this destructive process frequently attacks the surrounding textures merely in the character of suppuration, and that, as such, it may, whether based upon a benignant or upon a malignant new formation, either exhaust the organism, or, on the contrary, lead to a cure, - to the expulsion of the heterologous product.

5th. That where a fresh development of heterologous substance is excited and kept up in neighboring parts by inflammation connected with sustained ichorous secretion, the maKgnancy of the growth may be at least strongly suspected.

(e.) Malignant new growths are said to abound in albumen and casein; benignant new growths, in fibrin and gluten.

Were such a distinction of new formations not rendered nugatory by the convertibility of those organic substances, it would become in a great measure deprived of its value by the number and weight of the exceptions, - for example, those of fibrinous tubercle, of fibrous cancer, the composition of which is marked by a considerable amount of gluten, etc. (f.) Homoeoplastic formations are, for the most part, benignant, heteroplastic growths malignant.

Supposing such a distinction admitted, its utility would still be doubtful, seeing that in a given case the decision frequently depends upon the method followed in the examination, and upon individual opinion; and again, that in many new formations, homaeoplasia and heteroplasia coexist in various gradations. For the more marked repetitions of normal textures, namely, areolar, cartilaginous, osseous new growths, the character of benignancy might indeed be predicated; whilst, on the other hand, certain forms of malignant fibrous cancer bear so close a resemblance to the benignant fibroid new growth as to set discrimination at nought.