cells more granular than they should be, and some few whose nuclei are obscured by the little bright oily particles which FIG. 6. FIG. 6. Various cell-forms from a carcinomatous tumour. in others so fill the cells as to render its parts wholly undistinguishable. Having thus briefly described the typical stroma and cells of ordinary carcinoma, it is perhaps hardly necessary to state that these are not found in all the perfection of their most typical arrangement in every section of a carcinomatous tumour. Reference has been already made to the fact that the main distinction between hard and soft carcinoma lies in the proportion of the fibrous to the cellular elements. In the softer growths it is sometimes difficult to make out any fibrous stroma at all without careful pencilling, so delicate are the bands and so wide the meshes (see Plate V, fig. 4). In well-marked scirrhus, on the other hand (as shown in fig. 7), the alveolar arrangement is particularly conspicuous (see also Plate I, fig. 1). But in both of these cases it often happens that, from some defect in the mode of preparation or obscurity caused by excessive staining with carmine, the precise forms of the individual cells are by no means so easy to define as they are shown in these woodcuts. What one frequently sees is merely a number of dark clusters of cells, of which perchance the nuclei may be tolerably clear, imbedded in a pale, homogeneous, or fibrillated medium; but here much help is obtained by looking round the margin of the FIG. 7.—Typical mature carcinoma, from a scirrhous breast. Probably by the action of the chromic acid solution employed to harden the specimen, the cells have shrunk away from the alveolar wall to some extent. Magnified 220 times. section-for even if this be not sufficiently thin (and the edge of the roughest razor-section is generally fine enough for the purpose), the loose cells which float out abundantly into the glycerine in which the section floats are readily discernible, and display perfectly the shapes which are obscured in the denser portions of the specimen. Again, in some parts of such a tumour, field after field of the microscope will exhibit only a flat surface of fibrous texture in varying stages of development, and then, perhaps, a few irregular groups of cells will herald the approach of a confused mass of richly cellular structure, which may again as suddenly give place to considerable tracts of connective tissue, or remains of mammary gland, if it be a scirrhus of the breast which is under observation. Moreover, if the section be taken from the extreme margin of the scirrhous nodule some such appearance as is shown in fig. 8 is seen FIG. 8.-Developing carcinoma, from the extreme margin of a scirrhous nodule. The fibrous tissue to the left of the sketch is seen to be dotted with minute granular corpuscles, which are also collected in groups. To the right are the young, oval, nucleated cells of the tumour, arranged in elongated alveoli. Magnified 220 times. namely, a distribution through the fibrous tissue of small spherical corpuscles very like leucocytes (the "indifferent granulation material" of Virchow), at first in twos and threes, but soon in larger clusters, until these seem to change into the groups of larger oval nucleated cells, which are not very different from those of mature carcinoma. I say seem to change" advisedly, for it is very difficult to trace accurately these tissue transformations, and many eminent observers ascribe the origin of the cells of scirrhus to the glandular epithelium, whilst others are equally confident of their development from proliferating connective-tissue elements. It must be remembered, also, that recent observations upon the nature of leucocytes or wandering white blood-corpuscles render it possible that these furnish the starting-points for the cells of carcinoma as for those of many other new growths. It is scarcely necessary to discuss here the argument from this last hypothesis which might forcibly suggest itself to those who hold cancer to be a "blood disease." Just as we are beginning to be doubtful about the wisdom of dismissing the terms 66 exudation" and deposit," in favour of terms expressing more definitely the idea of local cell-proliferation, so it may be that the recent remarkable experiments of Professor Cohnheim and his followers may bring us again to accept the theory of a "blood disease" as the essential cause of the formation of malignant tumours; but it may be at least suggested that even if the first cells of a cancerous tumour be emigrants from the capillaries, the condition which determines their special development when once outside the vessel must depend solely upon some local change or aptitude or force in the tissues amongst which they are extravasated, for the same emigration of white blood-corpuscles is seen to be the first step in many widely different processes, as in inflammation and in the repair of wounds. In the present unsettled condition of pathological research, when the discovery of to-day is too apt to be classed with the mistakes of yesterday, we may be fairly excused some reluctance in accepting too unreservedly deductions from experiments made by different observers with conflicting results. Under these circumstances, it is prudent to confine ourselves to a statement of what is actually seen in an ordinary specimen of developing carcinoma, and not to trouble ourselves for the present about the true interpretation of these phenomena. To sum up this hasty review of the microscopic structure of carcinoma, its several stages of development, maturity, and decay may be illustrated by the accompanying diagram (fig. 9). First, we have an accumulation of small bodies resembling granulation corpuscles, which may be leucocytes or (more probably) the product of connective-tissue proliferation (a). These gradually form small clusters, and the next appearance is a series of groups of larger oval and nucleated cells (b). These, in their turn, give place to well-marked meshes in the fibrous material, filled with irregular densely-packed cells (c), a. FIG. 9.—Diagram representing the several stages of carcinoma. Granular corpuscles collecting into groups (connective-tissue proliferation ?). b. Young oval nucleated cells clustered together. c. Typical mature structure. d. Gradual withering by fatty degeneration of cell elements and shrinking of alveoli. the typical structure of carcinoma, and no sooner are these formed than symptoms of decay appear, the cells become gradually obscured by oily accumulation within them, burst, and the oil runs into larger drops; lastly, the connectivetissue corpuscles in the stroma may themselves degenerate; and then (d), we have merely a granular fibroid stroma enclosing spaces filled with oil particles, and in which the arrangement of the remains of the alveoli alone suggest to the observer the carcinoma which has flourished and withered. I have said that this form of malignant disease is specially typified in ordinary scirrhus of the breast, but the appearances |