PATHOLOGY 365 as may be observed in the tadpole s tail (Unterauchungen fiber die Entiuickeluny dcr Blutgcfdsse, Berlin, 1856, p. 30); and the circum stances are so little ana logous iu the two cases that this statement may be readily credited. How the new vessels join on to the old is not easily made out, whether in the placenta or in granula tions. As the granulations get older, the vessels acquire a considerable longitud inal coat of spindle-cells. The individual granula- FIO. 6. Young granulation-tissue, where the ves- tion-points on the surface sels are spaces bounded by rows of flattened become fused into a more cells - ( After Billroth.) uniform fleshy stratum, the lower layers contract as the cells approximate to fibrous tissue, and skin begins to form on the surface. If a healed surface be examined long after, in micro scopic sections through the skin and subjacent tissue, the parallel vessels will still be observed running at intervals towards the surface, only more obliquely than in the granulation-tissue, They are invested by a certain quantity of fibrous tissue arranged parallel to their course, while all the rest of the space between two of them is occupied by horizontal lines of fibrous tissue, with spindle- shaped cells lying regularly among the bundles. This change has been, first of spherical granulation - cells into spindle-shaped cells, with development of intercellular or perinuclear substance (fig. 7), and then fibrillation of the latter. It is worthy of note that a development into clastic fibres goes on in the .scar for months or even years after healing is complete. Hairs, hair - follicles, and se baceous glands are not repro duced are sweat _ hand, fat develops readily in the usual situations, s. Suppuration in Repair. Meanwhile there has been a remark able concomitant of the growth and adaptation of the reparative material, namely, a flow of pus or matter from the surface. Matter or pus varies in its physical characters somewhat ; it may be creamy and yellowish-white (pus laudabile) or greenish-white, or it may be thin and watery or more viscid. It has an alkaline reaction and a faintly sweetish odour. Standing in a vessel, it separates into two parts, a supernatant fluid or serosity, clear, and of a yellowish tint, and a sediment of pus-cells. The serum coagu lates when boiled, and it may even happen that a fibrinous clot forms in pus after death, just as in drawn blood. The serum of pus contains from 1 to 4 per cent, of albumen, and very much the same salts as blood -serum. The cells of pus are spherical elements of some what uniform size, of the greyish colour of protoplasm, granular on the surface, and disclosing the presence of two, three, or four nuclei when treated with acetic acid (fig. 8). They are capable of amoeboid movements, and they may be seen to take into their substance such particles as charcoal with which the wound may be dressed. Physiological Analogy of Pus. Pus is a very remarkable adjunct of the reparative process to go no farther FIG. 8. Pus-corpuscles, n, fresh; into the inflammatory processes for b . ""fler acetic acid the nuclei the present. The pus-cells are evi dently a condition or product of the granulation -cells on the extremities and sides of the vascular out growths, and they are detached from these situations, carrying with them a certain amount of fluid. Is there anything analogous to this in other formative processes of the body ? The following analogy is very close in some at least of the circumstances. The ts, and interior of a cyst removed by operation from the neck region is st-for- found to lie covered with vascular tufts, which have precisely the itions. character of granulations as regards the blood-vessels. Each vas cular tuft is covered by a cap of cells like a granulation, and the same investment of cells can be followed as a cylindrical column down the vessel into the depth of the cyst-wall. These cells are somewhat peculiar. They are cubical or polyhedric elements, with a ed in the skin of scars, nor Fl - 7 Vessels of granulation-tissue, their , i i ,-. ,, .-, walls invested by longitudinal spmdle- sweat-glands. On the other cclls . the lnter ^ al occupied by round cells or transverse spindle-cells. 0, visible ; c, blood-disks, to coin- pare in size. nucleus and a broad zone of protoplasm (fig. 9, ). On the summit and sides of a vascular tuft they are found becoming detached and dis integrated, the nucleus being cleft into fragments, which afterwards coalesce, while the cell-substance ilow^ off in the form of spherical or oval or pear-shaped vesicles of a reddish tint (tig. 9, b}. The cyst is a blood-cyst, its contents, a clear i brownish fluid with many red blood- disks floating in it, having been produced by the disintegration of the cells covering the vascular tufts. The cells are hrematoblasts; their cell-substance is disengaged in drops which afterwards become red blood-disks, and their nucleus, FIG. 0. n, perfect hfomatoblasts ; b, after being cleft into several fra"-- disintegrated hsematoblasts, the ments of unequal size is remade ^XS^lSSgR ? and survives as a cell of the size of mains of the ha-matoblasts, resem- a pus-cell, and containing several id ing pus-corpuscles in the cleavage nuclei like a pus-cell (fig. 9, c). This or dispersion of the nuclear particles, is a curious instance of blood-making from connective-tissue cells late in life, and it is not so much inexplicable in its characters as it is rare in its occurrence. The formation of pus on the granu lations of repair is one of the commonest of incidents, but it is open to elucidation even by a rare analogy. In the one case a blood-like fluid is formed, and in the other pus ; the fluid part of pus corresponds to the plasma together icith the red blood-disks in the cyst, and the cellular part of pus, the pus-corpuscle, corresponds to the surviving but broken-up nucleus of the hsematoblast. The granulation-cell is comparable to the perivascular cell of this blood- making process, and in passing into the condition of a pus-cell with several small nuclei it disengages merely a fluid plasma and no red blood-disks. The cells of the injured part having returned to an embryonic state, their first activity is a revival of early embryonic activity ; if they do not make blood, they yield that which may be regarded as its substitute, namely, pus. This analogy will appear all the closer from a consideration of another cyst. In this new growth, which occurred under the skin of the back, and was removed, like the former, by operation, the wall is lined by a certain thickness of tissue which is practically the same as the granulation-tissue of repair ; there are the same parallel vessels ending in loops, the same cells, and the same deliquescence of the surface. The fluid in the cyst is indeed the result of this liquefaction a somewhat turbid brownish fluid. In a small recess of the cyst there is a formation of a considerable layer of epidermis- like scales on the surface. One important point of difference is that the deeper layers of cells show no tendency to become spindle- shaped, to take a transverse order in the intervals between the parallel vessels, and so to become fibrous tissue. On the contrary, one finds in the depths of the tissue the steins of vessels surrounded by zones of young cells, perivascular sources of the new growth by which the loss of substance around the terminal loops of the vessels is constantly made good. On these terminal loops the process is not one of pus-formation, nor is it altogether one of blood-formation as in the former cyst ; but it is an intermediate process which helps us still further to understand the significance of the pus in repair. The new formation is comparable to that of the blood-cyst in the obvious perivascular grouping of its cells, and it is comparable to the granulations of repair in the forms of its cells ; and it thus supplies the link between the blood -yielding tufts of the former and the pus -yielding vascular points of the latter. What, then, is the nature of the deliquescence in the interior of this cyst ? It is partly blood ; and there may be seen also the large cells from whose proto- v plasm the blood-disks have been derived. There are also seen the remarkable cells with nucleus cleft into three or four, so like the cells of pus (fig. 10, b) ; the latter are the surviving nucleus of the hrematoblast, the peculiar form of which is best explained by watching the more perfect process of blood -formation on the wall of the FIG. 10. ff, large Wood- blood -cyst. Fewer of the cells in the second - Vle1 cyst undergo this transformation ; fewer of them ever attain the perfect form of hfrmato- blasts so as to be able to undergo it. For the most part they pursue a devious development, and it is in this that they resemble granulation-cells. The differ ence is only one of degree ; the type or law of the process is the hrematoblastic type, which may be more or less perfectly attained. We are accordingly confirmed in the impression that pus-cells are the surviving nuclei of embryonic cells whose perfect law is blood- making, and that the fluid which accompanies them is the cell-pro toplasm which has failed to disengage itself in the form of individual buds that easily pass into red blood-disks, but has become a veritable albuminous fluid. Pus, then, may be said to be blood absolutely I @@- O e
the wall of a cyst ; ?>, their nuclei sur viving after the de tachment of c, the red blood-disks.
