The idea which is most frequently obtained in regard to the matured foci of carcinoma, which have not been changed by retrograde metamor phoses (fatty degeneration, retraction) and which have received a typical signification, is partly due to the examination of the cut surface with the naked eye, and 'partly to the microscopic appearance of such cut surface. The naked eye appearance of a carcinoma of the breast is that of a grayish surface interwoven with paler, net-like meshes. No distinct capsule is perceptible at the periphery; we cannot separate the new growth from the adjoining normal tissue, as in the case of fibroid and sarcoma, but the tissue extends into the new growth (with more or less sharp bound aries), so that it is dovetailed into the tissue more in the form of rounded nodules and ganglions, or which, as diffuse infiltration, has scarcely caused a projection, but may indeed have caused a contraction. In the softer forms the neoplasm is white, reticulated, yellowish towards the centre of the nodule (by fatty degeneration, carcinoma reticulare, J. Muller) or en tirely yellow, and somewhat firmer and more grayish at the periphery. In the harder forms a firm, whitish, fibrous tissue is found in the centre, the periphery of the slightly uneven surface is yellowish-red (becoming darker on exposure to the air), homogeneous, fatty. If we draw the edge of a knife obliquely across the cut surface, a whitish, cloudy, and perhaps finely granular pap-like substance collects on the knife, the so-called "cancer juice." Microscopic examination of this cancer juice shows that it consists of large roundish and angular cells (cancer-cells), which are distinguished by large nuclei, and especially glistening nucleated bodies; occasionally also we find many fatty degenerated cells and granular fat detritus.
When we examine this carefully expressed cancer juice with a low power and without crushing it too much, we are soon convinced that the cells are placed together in large balls and branched cylinders, the con tours of which are tolerably distinct, without our being able to recognize a membrane. Sometimes structures are found, which present, with a very low power, very distinctly the forms of acinous and tubular glands, with out our being able to find cavities in them. If we now make fine sections of the parts from which the cancer juice was expressed and treat them according to modern methods, for observation with low and high powers, we •ifl get something similar to what is seen in Fig. 45. In a more or less firm frame-work of connective tissue are found tolerably large cells (from four to six times as large as white blood-corpuscles); these have partly fallen out; by shaking and teasing the preparation, they can be entirely removed, so that only the connective tissue frame-work or stroma (of the older authors) remains. This tissue was called "alveolar," and is considered as well as the cells contained therein as characteristic of carcinoma. The decisive signification of this alveolar structure for car cinoma has been only very recently shaken. We have learned that many sarcomas, myxomas, and lymphomas also have a similar and sometimes precisely the same " alveolar structure." But as the alveolar and plexi form sarcomas and myxomas, as well as lympho sarcomas are of the greatest rarity in the mamma, the structure described retains without doubt its characteristic signification for mammary carcinoma. For the older anatomists and histologists there was so little doubt that the neo plasms arose from a kind, even though peculiar, of coagulating exudation, that all parts of the neoplasm appeared as pathologically newly-formed. The chief endeavor next was not only to explain the origin of the strangely formed cells, but also of the connective tissue frame-work.
Rokitansky took the view that the connective tissue grow out in a knobby and dendritic manner and the cancer cells were included in it; and this process, derived chiefly from papilloma and villiform cancer, should lead to the formation of the carcinoma structure. It was soon shown, how ever, that such interstitial papillary growths were also present on cyst walls and in the hollow spaces of previously formed glandular spaces, but that the development of the cancer frame-work depended not on the neo plasm, but principally on the fact that the cell exuberances infiltrated the existing connective tissue of the gland, grew through it, and consequently the stroma of the carcinoma is nothing else than the old connective tissue of the organ, pressed asunder, in which and from which the carcinoma originates. This view is much advanced by the progress of developmental history, which teaches that the new cells are not separated from the amorphous blastema as crystals from a solution (Schwann), but that they only arise by budding and division of other cells. Now arises the ques tion: from what cells are the cancer-cells developed ? The more exact examinations of carcinoma, especially the examination of its boundaries, by which we hope to gain information regarding the development of the first pathological forms, show that there are almost always two kinds of cells to be found in carcinoma: 1, the larger, more epithelial-like form in the alveoli; and 2, smaller ones of the size of white blood corpuscles, more or less compressed and infiltrated between the fibres of the stroma (Fig. 45). That the first arise from one another by budding and division is easily seen by the recognized series of forms, which arise in this way. In the smaller infiltrated cells, no division forms are seen; whether they are developed by budding of the connective tissue cells, or whether they are white blood corpuscles, which have migrated from the vessels, remains uncertain; in favor of the last hypothesis is the circumstance that they are frequently seen heaped in masses around the small veins. As regards the origin of the epithelioid cancer cella it has long been doubtful whether they also sprang from connective-tissue cells (stabile, movable connective tissue bodies, endothelia) as do the small cells infiltrated in the stroma (V irchow), or whether they are offsprings of the glandular epithelial cells (Thiersch). Proof by direct observation will probably scarcely be fur nished; we must always recur to the combination of certain stages of the development, as well as to analogous embryonal growths, and here it is conceivable that absolute certainty will not be reached.' I have already accepted Virchow's opinion, and only granted the participation of the epithelial cells for those exceptional cases which I specially designated as epithelial carcinoma of the mamma. It is hard to understand why there is such an enormous difference in the size and 'form of the cells, which arise in the same place and from the same material; further, why at one time the cells, which have become large, collect in cylinders and bulbs, at another the cells which remain small are infiltrated in the con nective tissue. Newer observations have, it is true, taught that similar processes occur in alveolar and plexiform sarcomas; still, such a great difference in the proportion of their form and size scarcely ever takes place, with the single exception of giant-cell development, which is an especial attribute of many sarcomas and also of miliary tubercle.