size of a pigeon's egg, or more, then resembling a true encysted tumour. In its last changes, if not discharged by the fistula remaining after the operation, it withers and remains undisturbed among the tissues where it lies, or terminates by being with its cyst completely absorbed." (pp. 21, 22.)

The author took the necessary precautions to prevent the escape of the ligature, so that the fact of absorption was in many instances demonstrated. The plates contain several illustrations of each of these various effects of the catgut ligature. In thirty-three of eighty cases the catgut had completely disappeared, and in several others it was found so much softened that little doubt could be entertained of its progressive absorption.

More experiments were made with silk than with any other material, both in the manufactured and crude state, untwisting the threads of commerce and applying them not thicker than a human hair. The only difference in the results was, that manufactured silk left on an artery lost its artificial colour, while the unprepared maintained the white or yellowish colour natural to it.

When compared with catgut, silk ligatures produced much more irritation, and excited suppuration more frequently, although in many cases simple adhesive inflammation alone was produced. Like the catgut, they are first covered with plastic lymph, then connected with the cord remaining between the two extremities of the artery, or they lie bare between the layers of the common cellular tissue, or become encysted. If not thrown off, the silk may remain inert during life; yet in some cases the author says he has succeeded in demonstrating that after a long time it becomes softened, and may be absorbed. In one hundred and twenty experiments the ligature was discovered in one hundred and one cases, in nineteen (a sixth) it disappeared; in some of them it may have escaped observation, but as in most of those discovered the silk had undergone a gradual change, and great care was taken in the examination, the possibility of the absorption of silk cannot be denied.

No difference was found between slender ligatures of linen or hempen thread. They were not at all more irritating than silk. Of sixty cases, in three or four only did an abscess form, in all the others adhesion followed; and when they were applied merely as a loose knot, frequently, after the course of some months, they were found lying innocuous upon the uninjured and pervious artery. After an interval of two years, like catgut and silk, they are found either in a state of perfect integrity, or macerated, or completely removed. Fifty were found, ten had disappeared, and most of those found were in the stage of metamorphosis.

Forty experiments were made with black horse-hair, single and double, and the observations have been prolonged to three years. The only difference between the hair ligatures and the others is, that they preserve their physical properties unaltered, and still remain in the body innocuous. Of the forty ligatures thirty-eight were found. Of the two which disappeared, one was applied upon a sheep, and could not be found after seven months; whilst others of silk and thread, upon other arteries of the same animal, were found. The other was upon the carotid of a dog. It is much more probable that the ligatures escape unobserved than that they are absorbed, and thus regarded, they tend to confirm the correctness of

the former observations. Human hair has been tied upon the arteries of rabbits, and, like horse-hair, has always been found unaltered. During fifteen years the author has applied ligatures upon the principal arteries after amputation, wounds, or in cases of aneurism, and disease, in upwards of one hundred cases, and the comparative results in men and animals, with regard to the alterations in the ligature and its effects, show that suppuration is much more common in the human subject; that the ligatures, if left, almost always escape, sooner or later, either from the original wound or a secondary opening; but that in some cases of amputation, followed by union by first intention, when both ends of the ligature had been cut close off, they had remained in the limb and never appeared. Hennen, Veitch, and Lawrence have observed the same fact. Certain cases recorded by Porta and other authors tend to prove that when the ligature remains in the human body it undergoes the same series of changes as in the lower animals. The chapter is concluded by a table, which we give entire, as the results are practical and important:

This table is alone sufficient to show the care and industry of Dr. Porta; out we must pass without further comment to the succeeding chapter of his work, on the methods of ligature and torsion, and of the pathological conditions induced by them in arteries.

II. There are four methods of employing the ligature in the continuity of the trunk of an artery: 1, tying it round and leaving the ligature; 2, removing the ligature immediately after applying it; 3, interposing a foreign body beneath the ligature; 4, applying the ligatures and dividing the artery between them.

The common method of circular ligature is first treated, and a number of experiments are related, which were instituted for the purpose of determining the consecutive changes at different periods. Without the plates we could not convey any correct or clear idea of these changes in individual cases, and we must therefore be content, as before, with an analysis of the conclusions of the author, upon the result of one hundred and forty experiments:

"The circular ligature applied upon an artery determines the following mechanical alterations: division of the proper coats, strangulation of the cellular coat, and their approximation internally at each side of the ligature with the formation of a clot. In this condition the artery, in consequence of the operation, is subject to two kinds of inflammation, the adhesive and the suppurative. The experiments just related demonstrate the first kind, or obliteration by adhesion.

"The process of coalition of the tied artery has four periods: the first, external arteritis and organization of the oliva cellulare; [this implies a quantity of coagulable lymph exuded, covering the ligature, and taking the shape of an olive ;] the second, closure of the vessel; the third, isolation of the closed extremities, and detachment of the ligature from the intermediate cord; the fourth, assimilation of all these parts......

"The rapidity of the organization of lymph is extraordinary, beyond belief. At the close of the second to the third day the oliva is changed into a gelatinous tissue; and generally in less than a week the new cellular sheath is perfectly formed, and presents a most beautiful and beneficial provision of nature for the obliteration of the artery, and protection against the blood which threatens its future destruction." (pp. 53, 54.)

We pass over a minute account, more curious than important, of the other stages of the process, but extract a passage on the formation of the internal plug, or clot:

"The trombo, or internal coagulum, is among the first phenomena of the ligature of an artery, and arises, as it is known, from the stoppage of the blood between the ligature and the first lateral vessels. This purely physical phenomenon is general in tied arteries, but not so constant as to be observed in all cases. Of one hundred and forty experiments with the circular ligature the clot was not formed in twenty-nine, sometimes on neither side, and more frequently only on the side next the heart, or vice versa, and this without neighbouring lateral vessels: several times the clot has not formed, and the artery has remained permanently empty, notwithstanding an interval of some millimeters from these vessels. When the clot forms it may take place in a few hours, or in the first day; or the blood may not be completely coagulated on the third or fourth day. The larger a vessel is, the nearer the heart, subordinate to the action of this organ, and rich in lateral branches, the longer is the clot in forming, it is weaker, or is altogether wanting. It is also erroneous to suppose that the clot is always formed in proportion to the capacity of the tied trunk, and to the distance of the first lateral branches; not

unfrequently the clot is excessive, and passes beyond small and large lateral emissaries one or two millimeters in diameter; while in other cases it remains short, or slender and thread-like, and only fills a part of the channel. When largest, it scarcely forms a plug, or completely fills the closed end of the artery, exactly uniting its walls.........Once formed the clot remains a long time unabsorbed, prolongs the process of assimilation, and it appears that it sometimes becomes permanent, traces being discovered several years after an operation; but when the artery goes through its last changes, the coagulum becomes white, hard, firm, almost calcareous, attenuated, forms part of the ligamentous walls of the vessel, and then entirely disappears." (pp. 56, 57.)

Travers and Jones believed that a division of the proper coats of the artery was necessary to the success of the operation, but our author states that it is not indispensable. In many of his experiments, particularly with catgut, he found that he had not divided these coats; yet the channel of the artery was closed, and the result the same as in case of division. The obliteration then occurs in two modes: either by coalition and simultaneous assimilation of all three coats at the spot tied; or by a slow and insensible contraction, which, after the obstruction of the clot, without destruction of the walls, renders the arterial tube impervious, and converts it in time into a ligamentous cord. But more frequently the ligature which does not at first mechanically divide the arterial tube, does so afterwards by the inflammatory process.

Besides obliteration by coalition, an artery may be closed also by suppuration. This is uncommon, however, in the lower animals, and is generally attributed to violence in the operation, motion, the introduction of foreign bodies, &c. Most commonly a little pus is formed in the centre of the lymph effused around the ligature, and this pus is reabsorbed. Complete suppuration without lymph is much more rare. When it occurs the tied ends of the artery lie in the middle of an abscess, separated from each other, with their coats soft and yellowish, and the opening of the canal closed only by the clot, which is the sole protection against hemorrhage for one or two weeks. As the suppurative process ceases, granulations spring up from the cellular coat and cellular tissue around the ends of the artery, and by their contraction the coats of the artery are brought together, and the opening is permanently closed. The artery, when thus cicatrized by the second intention, afterwards presents the same conditions as if it had united by primary coalition. A number of cases from the author's experience, and that of others, are given to show that the same changes occur in the human subject. But

"The two kinds of inflammation above described have an inverse ratio of frequency in man and in brutes. It is very rare, and only from extraordinary circumstances, that a complete suppuration with total separation of the ends of the tied artery occurs in brutes; and it is rare that a perfect coalition is effected in our arteries. And as this is the most simple, ready, and prompt mode of closing vessels, we see how much more fortunate animals are than man in this respect.

Operating in whatever manner, we can never expect in surgery the fortunate results from the ligature of arteries that are obtained in the lower animals; but, judging from analogy and from known data, I believe that when ligature of arteries shall be performed in man with greater delicacy than has been hitherto employed, selecting the most homogeneous material and the most simple method, respecting the cellular matrix of the vessel, cutting off the ends of the ligature, reuniting the wound, avoiding proximity to the aneurism, and enjoining the most perfect quiet

to the patient, we shall obtain adhesion more frequently; and when, notwithstanding our care, suppuration comes on, it will be circumscribed, and not always prevent a plastic exudation which can close the mouths of the artery, and prevent those fearful accidents which, very rare in brutes, have so often put the life of man in danger." (p. 74.)

We now pass to a consideration of the other methods of tying arteries : 1, temporary ligature; 2, mediate ligature; and, 3, double ligature, with

division of the vessel.

1. The method of ablation may be defined thus: the removal of a circular ligature immediately after its application upon an artery, and closure of the wound. In order to determine if this method was sufficient to excite inflammation of the coats of the artery, and thereby obliterate its canal, the author made a number of experiments, which he records. They were fifty in number, and made upon the principal arteries of various animals, dividing in every case the proper coats of the vessel with the ligature, and removing it at various periods from a minute to some hours. Division of the proper coats, and strangulation of the cellular, is produced, and the latter becomes inflamed for some lines in extent, and causes a lymphatic exudation, becoming restored to its normal state about the third or fourth week; very rarely the inflammation is greater, and the same coat is thickened, hardened, and contracted, and, remaining so, compresses the other coats, and diminishes the caliber of the vessel; suppuration is rarely produced.

Immediately after the removal of the ligature the tube is free to the current of blood, and is permanently pervious, uninfluenced by the division of the proper coats of the artery; while, on the other hand, these coats do not appear to be influenced in the changes they undergo by the sanguineous current incessantly passing along. It is only when the cellular coat is thickened, as before described, that the caliber of the vessel is sensibly diminished. Still, in some rare cases, a clot forms which obliterates the vessel, or arteritis follows, and external exudation of lymph produces the same result. Of the fifty cases, in six or seven a clot formed, and in five or six, lymph, or false membrane, which occupied totally or partially the canal of the artery.

Mr. Travers had preceded the author in these experiments. He left the ligature from two to twenty-four hours; and in eleven experiments upon the carotids of horses and asses he almost always obtained obstruction of the vessel by sanguineous or albuminous coagulum. His papers in the fourth and sixth volumes of the Medico-Chirurgical Transactions are well worth attentive perusal. Dr. Porta, in addition to the fifty trials above noticed, made twenty-four others, removing the ligatures at two, six, and twelve hours. In one or two cases obliteration followed, but in the majority it did not occur; the clot and coagulum were wanting, and the caliber of the vessel was not diminished. Travers, Copeland, Roberts, and Crampton have adopted this method in some cases of aneurism in the human subject. In one case a popliteal aneurism remained pervious after ligature for twenty-six hours, another after six hours; one of aneurism at the elbow was cured by ligature of the brachial removed after forty hours, and another after popliteal aneurism of the femoral removed after twenty-four hours.