series of cases explain the author's propositions. The symptoms manifested during life depend on the ischemia of the part provided by the obturated artery, combined with collateral fluxion; they must therefore vary with the locality, the size, and nature of the embolus. The paleness, coldness, and loss of turgor may be so intense as to justify Cruveilhier's term "cadaverisation." Amongst the functional disturbances of the extremities, the neuralgia stands foremost; hyperæsthesia, paræsthesia, anaesthesia, and paralysis, are likewise met with. Plugging of the cerebral arteries may produce the well-known symptoms of tying of the carotids. Soon the ischaemic symptoms become mixed with those produced by the collateral circulation, frequently leading to hyperemia and its consequences-sometimes even to inflammation. In most instances, however, these secondary changes appear to belong to the retrogressive metamorphosis, or are of the necrotic nature. Thus we meet with softening of the brain (already compared by Rostan with senile gangrene), instances of which we have also in the cases of Rühle, Kirkes, and others.

c. Generally obturating coagula are combined only with necrotic processes. The coagulation in all the arteries of a certain district points to impediments of the circulation, and particularly of the capillary circulation. The impossibility of the entrance of blood into the capillaries acts like a ligature on the arteries; coagulation in the direction towards the heart is the necessary consequence. Thus the hæmorrhagic infarctus may cause coagulation in the arteries of the district, and at the same time necrosis of the part itself, by depriving it of its nutriment. Concerning the connexion of gangrene with the obturation of arteries, Virchow sums up his observations in the following

manner:

"Obturation of arteries may produce, but does not always produce, gangrene; gangrene may occasion obturation of arteries, but does not always occasion it; gangrene and obturation may be, but are not necessarily, joint effects of the same cause." (p. 450.)

Obturation of the Mesenteric Artery by an Immigrated Plug+ (pp. 456-58).—Of particular interest in this case is the hyperemia, and even fibrinous exudation in the parts supplied by the obturated artery. Virchow appears inclined to attribute this circumstance to the impaired nutrition of the vessels, which, according to this view, would be more easily distended, and even ruptured by collateral influx of blood.

Phlogosis and Thrombosis in the Vascular System (pp. 458-636). -In the essay on acute arteritis, the author was led, as we have seen, to the inference that the processes within the cavity of the vessels depend on thrombosis or coagulation, while the primary phenomena of inflammation are confined to the walls. Inflammatory, Virchow calls those active pathological processes which proceed from irritation, therefore the irritative disturbances of nutrition. Such pathological

* Ischemia, a term formerly employed by Peter Frank, is applied by Virchow to states of local arterial anæmia, in which the blood is prevented from flowing into those parts for which it is destined. (p. 304.)

↑ Verhandl. der Würzburg Gesellsch., Band iv. p. 341.

processes he describes: a, in the sheaths of the vessels (periarteriitis and periphlebitis), leading to suppuration, to callosities, &c. ; b, in the middle layers (mesarteriitis, mesophlebitis); c, in the internal membrane (endarteriitis and endophlebitis). Regarding this internal membrane, it will be remembered that the author, in his earlier publications, considered its alterations by irritation as of secondary and passive nature. At present, he still looks upon it as a kind of barrier against the changes of the middle coat in the acute forms of inflammation, yet he attributes to it also in these forms certain parenchymatous alterations; but much more important are the alterations in the chronic inflammation. He agrees with those pathologists (Bizot, Rayer, Tiedemann, Engel, Dittrich, and others), who derive those gelatinous and so-called semi-cartilaginous layers of the membranes of arteries from a chronic inflammatory process, as well as also those calcareous and fatty deposits, and the superficial ulcerations.

"It is of an as inflammatory nature," he says, "as the endocarditis, with which it is frequently in direct connexion, and as the so-called malum senile articulorum, the arthritis sicca s. villosa of some later authors; or as Burns proposed, the arthritis deformans. It may very well be named endarteriitis deformans s. nodosa."

The author, however, urges the necessity of distinguishing from the inflammatory atheromatous process simple fatty degeneration, which may take place as well in the heart as in all the membranes of the vascular system, and is so well described by Paget, and later by Moosherr, with respect to the capillaries of the brain. The atheromatous processes have their origin in the parenchymatous inflammation of the internal membrane. They commence in general with a slight swelling of the lining membrane (most distinct on the valves of the heart, the aorta and pulmonary artery), either in patches or in a more diffuse manner; the affected parts contain more fluid substance, by which the whole tissue may have a gelatinous appearance (the gelatinous or albuminous exudations of Bizot, Engel, Lebert, and others). Virchow is of opinion that this increase of substance is partly due to imbibition from the blood (analogy with tissues unprovided with vessels), but he proves, besides water, albumen, &c., the presence of another substance similar in reaction and microscopic aspect to fluid mucus, with many small round cells, often in the process of subdivision, and some larger ones spindle-shaped. The change consists, therefore, not merely in imbibition, but a morbidly increased metamorphosis with new formation, a species of hyperplasia. At the same time the fibres of the original tissue are frequently seen thickened, the cells enlarged with filiform ramifications, &c. Besides the gelatinous swellings, we meet often with harder "semicartilaginous" spots, which may be the product of a further alteration of the former (Lobstein's arteriosclerosis). The sclerotic patches usually undergo the atheromatous process; while the gelatinous swellings pass likewise through the medium of fatty metamorphosis, but terminate in softening and superficial ulcerations (fettige Usur); the latter is most distinctly seen in the pulmonary artery, the formation of the atheroma in the aorta. • Ueber der Pathol. Verhalten der Kleinen Hirngefässe. Würzburg, 1854.

The calcification, which sometimes takes place in the semicartilaginous patches, is regarded as real ossification, on account of the analogous transformation of the cellular elements. Regarding the etiology, Virchow does not follow Bichat and Rokitansky in ascribing any importance to the arteriality of the blood, but attributes the principal influence to mechanical moments (Rayer, Dittrich), without, however, altogether denying the existence of a dyscratic predisposing condition. The occurrence also of a chronic endophlebitis is another weight against the view that the arterial quality of the blood is the cause of the alterations in the lining membrane of the arteries; the endophlebitis is, however, of rarer occurrence, and terminates less frequently in atheroma than in ossification.

In endocarditis, too, the mechanical moments are of great influence, as Hope has already explained. On the endocardium, as on the lining membranes of the arteries, the phenomena of merely retrogressive metamorphosis are not to be mistaken for those dependent on inflammation. The latter are analogous to those met with in the arteries and veins; here again we meet at first with the small gelatinous thickenings, principally towards the free edge of the valves; later only these are changed into more tense or semicartilaginous masses, which in a still later period may undergo the fatty (atheromatous) metamorphosis or ossification. The endocarditis, however, runs a more acute course, on account perhaps of the larger number of vessels, and the looser cellular tissue beneath the endocardium; through this medium there is here a greater tendency to the formation of warty excrescences, which may give rise to the deposition of fibrinous coagula from the blood, the origin of which is of course altogether different.

Concerning the composition of the thrombus, it differs from a simple blood coagulum by its distinctly stratiform construction, by its larger per centage of fibrin, by containing a greater number of colourless blood globules. With regard to the circumstances under which a thrombus is formed, we find that retardation of the circulation is the condition which is common to all varieties of thrombosis; but how, in the retarded or stagnating blood, the change in the "fibrinogenous substance" is effected, without which the coagulation does not take place, is a further question which had not yet been answered to the author's satisfaction. Malherbe's theory of the superfibrination of the blood, Vogel's hypothesis of the inopexia (i.e., increased coagulability of the fibrin), Paget's view regarding the influence of urea, Engel's, Millington's, and Lee's concerning the action of pus admixed to the blood, all these suppositions appear not sufficient to explain the fact of the coagulation within the vessels. Referring to one of his former "On the Origin of Fibrin, &c.," Virchow repeats that the influence of oxygen is necessary to effect the coagulation of the "fibrinogenous substance;" this oxygen, when not admitted through lesions of continuity, must be developed within the blood itself, and he is inclined to find the source for this in the spontaneous decomposition of the blood-globules in the stagnating blood."

essays

With respect to the relation between phlogosis and thrombosis in the vascular system, there is no doubt that they are mutually inter

dependent; but primary thrombosis is much more frequent than primary phlogosis. Phlogosis induces thrombosis principally in cases of endocarditis, when the roughened or ulcerated surface causes deposition of fibrin on the walls; and further, in suppurating inflammation or necrosis of the membranes.

In concluding this chapter Virchow treats on some of the principal varieties of thrombosis. 1. The marantic* thrombosis (the spontaneous, rheumatic, or metastatic phlebitis of some other authors) is the most frequent form, and may be induced by many debilitating diseases; in consequence of the diminished power of the heart the circulation becomes retarded in the most distant points, especially the veins of the extremities, the pelvis, and the cerebral sinus. The commencement of the nucleus of the thrombus is, in general, situated behind the valves, exactly in the angle in which these are attached to the veins. 2. Thrombosis through compression (ligature, dislocation of bones, &c.) 3. Thrombosis through dilatation (varices, aneurisms, teleangiectasiæ, &c.) 4. The traumatic thrombosis; a, thrombosis from venæsection; b, from amputation. 5. Thrombosis of new-born children, analogous in some respects to that from amputation, and the forms of foetal thrombosis. 6. Puerperal thrombosis. A moderate degree of placentar thrombosis is a physiological process, only by too great extension (incomplete contraction of the uterus) it becomes pathological, approaching in its origin the venæsection-thrombosis; but the marantic form, that from dilatation and compression, may coexist. 7. Secondary thrombosis, through inflammation of the coats of vessels. The inflammation most frequently leading to thrombosis is the suppurative variety, during which, through the ruptured internal membrane, pus may enter into the cavity of the vessel; the thrombosis, however, is, in general, formed before the perforation of the internal membrane; it thus prevents at first the admixture of pus with the blood, but by degrees it breaks off, or deliquesces, or may undergo an ichorous metamorphosis, and may propagate the contamination to the blood itself. All these varieties of thrombosis, as also the other subjects treated of, are elucidated by a large number of well-described and well-adapted cases, which form an important element in the whole volume-a circumstance through which its value is greatly increased.

Embolia and Infection (pp. 636 ss.)—The discussion of the doctrine of pyæmia leads to the examination of the question, whether the principal symptoms are to be considered as produced by the mechanical (globules) or by the chemical action (absorption of the serum) of the pus? The theory of the irritating or obstructing nature of the pus-globules appears perfectly inadequate to explain, by itself, the phenomena ascribed to pyæmia; these must be divided into two series, the one depending on mechanical, the other on chemical influences, or, in other words, into the phenomena of embolia and infection; both are frequently combined, but more frequently separated. The theory of the mechanical metastasis of pus has lost much of its plausibility, since we know that the metastatic abscess is not formed by a mere metastasis of pus, but is originated by a lobular suppurating inflamμapaσμós=μápavots, the witheredness, tabefaction, atrophy, etc.

mation. Through this fact the purulent diathesis has become another form of inflammatory diathesis, characterized, however, by a tendency to suppuration. This inflammatory-purulent diathesis can, in many instances, not be explained by the admixture of pus globulesi.e., the mechanical element- as the phenomena of small-pox, of syphilis, and glanders clearly show; but these conditions point to chemical actions. The author here proposes three questions: the first, regarding the diagnosis of the presence of pus in the blood, has been treated of already in the section on leukæmia; the second, concerning the artificial production of the so-called purulent diathesis, induced him to try the injection of various fluids into the veins of dogs : a, admixture of putrid fluids (the products of simple putrefaction of animal substances, as water from putrescent fibrin), did not produce evident metastasis, and caused death sometimes without abscesses (Castelnau and Ducrest); but the author considers this subject as yet as insufficiently examined; b, the injection of pus led to the following results-1. Normal, fresh, not specific, pus does not produce, when carefully injected, perceptible anatomical alterations, especially no metastasis-an inference which agrees with those of Dupuytren and A. Boyer. 2. The same operation performed with unfiltered, or very coherent pus, principally when a large quantity is injected in a short time, is followed by the formation of many centres of inflammation and suppuration. 3. When the injected pus is putrid, or specific, these secondary centres have the same character. 4. Injections into the arteries have the same effect as those into the veins. 5. A great part of the consecutive anatomical lesions is to be ascribed to thrombosis which may be caused by the ingestion of accidentally admixed blood coagula, and is not the necessary consequence of the injection of pus. The answer to the third question, namely, "Is the injection of real pus into the blood to be considered as the cause of the pyæmic phenomena in man?" is based on the result of the previous researches and on the analysis of some additional cases.

"The existence of pus in the blood," Virchow says, "cannot, as I have endeavoured to explain, be proved with certainty. The absorption of pus in substance we were obliged to refute, the aspiration of pus has been limited to few instances; the perforation of abscesses into veins has been designated as a rare occurrence. Finally, we have been able to demonstrate that suppurative phlebitis, as a rule, is the product of thrombosis, and that venous pus is the detritus of fibrin and blood-globules." (p. 665.)

On the other side it cannot be denied, after a careful examination of many cases of pyæmia, that they are caused by an alteration in the blood; it further cannot be doubted, that foreign substances may enter the blood from the primary centres of disease; it also appears probable that the principal part of this absorption is not performed by the veins situated in the diseased or wounded spot itself, as they are in general filled with a thrombus, but by the nearest of those ramifying in the neighbourhood in which the circulation continues, as also by the lymphatics. By this assertion, Virchow, of course, does not exclude the possibility of the absorption of fluid substances contained and formed in the thrombus itself. Regarding the chemical nature of the