Heterologous growths not distinguishable from sarcomata by definite generic marks, and, like these, to be dealt with only as species, but contrasting with sarcomata in the single feature, common to them all, of malignancy. Carcinomata originate and subsist not rarely as local evils. Far more commonly, however, they are associated with a dyscrasis, which, in point of fact, often precedes and engenders the cancer. Hence the multiple appearance of carcinoma as the sequel to a single one, as the sequel to the extirpation of a voluminous and hitherto solitary one. Hence, in other cases, the original appearance of cancer in several organs simultaneously, or in rapid succession.

Conformably herewith, carcinomata can rarely with adequate reason be attributed to external local causes, whilst it is very common for them to luxuriate in internal organs beyond the reach of palpable influence from without.

The crasis which gives rise to the production of cancer, consists mainly in a preponderance of albumen, a defibrination (hypinosis), for the particulars of which we must refer to the doctrine of crasis. Concurrently with this we have, more especially in the medullary crasis, an excess of fat in the circulating fluid, which determines a complication of cancer to be discussed in a more appropriate place; and, again, that remarkable relation of exclusiveness towards ordinary, fibrinous tubercle.

This crasis is essentially the same for all cancers, only exquisitely developed in the medullary form. This may be inferred, at least, from the frequent concurrence of various cancer species, in primitive or consecutive combination, either in the same locality, or in different organs. It may also be inferred from the circumstance that, after extirpation, the one is replaced by the other under the same contingencies, and that, conforming with an augmentation of the crasis, the medullary cancer is generally the consecutive one, more especially where the substitution takes place rapidly.

The highest grades of cancer-crasis originate through infection, that is, through the reception into the lymphatics, or more especially into the bloodvessels, of cancer-cells, or of cancer-blastema, of a lax, soft, semi-fluid character. The blastema is carried thither by imbibition, partly in the mere act of nutrition, partly, with or without the cancer-cells, through the lymphatics or veins laid open by ulceration of the tumor, or lastly, by the cancer penetrating into the canals of bloodvessels. Infection thus brought about, occasions locally, or it may be remotely, both in large bloodvessels and in the capillaries, coagulations of blood. In the former case, these are cylindrical, branched, plug-like, or clavate coagula, adhering to the internal bloodvessel membrane, or to the endocardium (vegetations). They reveal their cancerous nature by their external medullary characters, as well as by their vigorous growth. In the capillaries the coagulation assumes the form of the cancerous depot - so called metastasis (capillary phlebitis).

Cancer-formation assumes both a chronic and an acute course, the former being the more ordinary mode of occurrence for primitive cancer; whilst secondary cancer production is brought about with more and more rapidity in proportion as the cancers multiply. Ulceration and extirpation of carcinoma are especially apt to determine its very acute secondary formation. Still there are instances of highly acute, primitive, general cancer production. Moreover, the individual species of cancer manifest marked differences in this respect, both the first development and the ulterior growth, for example, of fibrous cancer, being slow, whilst in the case of medullary cancer they are incomparably more rapid.

In primitive cancers, the blastema is, in the great majority, insensibly produced. In acute cancer-formation it is thrown out under the symptoms of hyperaemia, and occasionally of inflammation. In the latter case, it often covers serous membranes with a stratiform cancer exudate, or infiltrates and hepatizes the lungs with cancerous tubercles. From what has been said, our opinion may be inferred respecting the seat of cancer, in opposition to that of Carswell and Cruveilheir, who refer its origin to the capillary system. But, although in the ordinary process of cancer-formation we look upon the blastema as an exudate in its broadest sense, we by no means question the origin of cancer from coagulation within the bloodvessels after the type of depot-formation in general (see Metastasis). It is indeed to this mode of development that we would ascribe the rapid cancer-formation engendered, in brutes, by the injection of cancer-blastema.

We are further disposed - although from isolated facts only - to believe in cancer-formation, through a conversion of certain physiological elements into those of cancer. In the liver, namely, we occasionally light upon a process, limited to circumscribed patches, of pallescence and alteration of the parenchyma, with some augmentation of its volume. Upon further examination, the portion of liver so affected is found to consist indubitably of hepatic cells, more or less bereft of their biliary and coloring matter, and of an intermediate, whitish, albuminous blas-tema, - as though the hepatic cell had become transformed into the cell of medullary carcinoma.

Cancers present sometimes well-defined, easily removable, spherical, irregularly knobbed, lobulated, branched tumors, which may lose their circumscribed character, only during their progress, by insinuating themselves betwixt the elements of textures hitherto merely displaced. Or they may appear, from the first, as infiltrated heterologous masses, involving the textures without definite limits. When an established cancerous mass stretches forth from one organ to seize upon a second, the latter is forcibly drawn in the direction of the first. Membranous formations, in particular, become attached to it with umbilical flattening, waste away, and become perforated by the heterologous mass. This is especially the case with fibro-carcinoma.