ally a dull second sound. I have never heard a diastolic murmur. In some instances systolic murmur is audible in the reclining, when inaudible in the erect posture. Dr. Corrigan supposes this explicable by the removal of hydrostatic pressure in the former position, and the consequent greater freedom of the current in and out of the sac; but systolic murmur may be totally absent in every possible posture.

The size of the sac may be apparently increased by the extravasation of blood behind the peritoneum: this may occur on several successive occasions, and for some time before death (case of Hallington.)

There may be a total absence of all positive physical signs, -neither impulse, murmur nor percussion-dulness: the subjective symptoms are then very likely to deceive.

II. Pain following the course of nerves implicated by pressure-passing along the edge of the ileum down the thigh to the testicles, &c.—and in character raw, sore, pricking, cordlike, plunging, hot and burning or cold, accompanied with spasmodic difficulty in passing urine, and with tonic contraction of the flexor muscles and inability to straighten the limb, the whole accompanied with peculiar gnawing vertebral pain, existed in a case where the sac sprang from the bifurcation of the aorta, encroaching a little on the left common iliac. But obviously the neuralgic sufferings must vary with the exact site of the sac. Theoretically, anasarca of the lower limbs, or of one of them, must occur, according as the inferior cava or either iliac vein is pressed on; but in practice either effect is most rare. Wasting of the testicles I have seen from obliteration of the spermatic artery. Pressure on the descending or transverse colon may obstruct the bowels, and cause flatulence and great labour in defecation; yet there may be no hemorrhoids (Hallington.) The urine may be rendered albuminous by renal congestion induced by pressure on the emulgent vein; otherwise it is perfectly natural, as far as the aneurism is concerned. The respiration, if the sac is low down, is of natural frequency and character; when high, it interferes with phrenic action, throws the onus on the ribs, and accelerates the act somewhat.

III. Death may occur by rupture of the sac behind or into the peritonæum, into the pleura, lung, colon, renal, pelvis, mediastinum, &c., or without rupture by jaundice, gangrene, exhaustion, &c. In some instances these sacs have acquired enormous bulk: one preserved in the Fort Pitt Museum is said

to have contained ten pounds' weight of coagula. Hence the inference that the gradual growth of the disease is not incompatible with life.

IV. The difficulties sometimes arising in the distinction of mere aortic pulsation from aneurism have already been considered. Facal accumulation is distinguished generally by the oval outline of the fulness; by its doughy inelastic feel; by the existence of several spots of dull and clear resonance under percussion, close to each other, and within the area of the swelling, from the intermixture of gas with solidified fæces; sometimes from the position of the mass; and generally, from the history of the case. The pains of aneurism may be imperfectly imitated by those of peritoneal distention from the enlargement of the bowel; but it is rare indeed that a mass of fæces receives such arterial impulse from behind as to simulate that of aneurism. In the obscurity of their early symptoms, in the eventual pain, and in the gradual exhaustion they produce, there is considerable similarity between lumbar and psoas abscesses and aneurism; but the swelling of these abscesses passes in an elongated form from above downwards, and does not exhibit an irregularly globular one like aneurism: they give neither impulse nor murmur. Tenderness exists in the lumbar spine, and there may be loss of motor power in the lower extremities; but the actual pain is materially less, as a rule, than in the aortic disease. Tubercles should be sought for in the lungs their presence would be directly in favour of lumbar abscess (of tubercular origin;) against aneurism. Hydronephrosis and pyelitic distention are accompanied with renal symptoms, changes in the urine, tumour with the character of renal enlargement,a tumour of tuberous nodular outline, non-impulsive, murmurless, and extending further into the flank and into the back than aneurism. The urine may be albuminous in all three affections.

V. The treatment is the same as of intra-thoracic aneurisms in general. Were the disease diagnosticated at an early period, might any good be effected by pressure either on, above or below the sac?-a cautious trial of one or other form of pressure might with propriety be made.

Group d.-Dissecting Aneurisms.-The morbid anatomy of dissecting aneurism of the aorta, in its three essential varieties, is clearly demonstrable from existing records: its clinical history has yet to be worked out. And, indeed, from the nature of

things it seems singularly unlikely that any general account, applicable even to the majority of such cases, can be given,— seeing that the symptoms must in great part depend upon the extent and precise portion of the aorta affected.

The symptoms in recorded cases may clearly be referred to three heads, which the observer should always aim at severally distinguishing; namely, (1.) symptoms of shock to the system at large; (2.) of dynamic disturbance of the artery; and (3.) of mechanical interference with function. (1.) The symptoms of shock are, primarily, sudden faintness or actual syncope, and, on recovery of consciousness, nausea, vomiting, and pain in the thorax or abdomen: secondarily, febrile action (by no means necessarily very marked,) thirst, furred tongue, abdominal tympanitis. (2.) The dynamic disturbances of the artery are signified by more or less severe pain in its course, and throbbing action, irregular in force and rhythm. (3.) The symptoms of mechanical origin are produced by the accumulation of the blood, filtrated between the coats of the aorta, against the orifices of arterial branches, whereby these are completely, or almost completely, blocked up. The nature of these symptoms will, of course, depend on the distribution of the blocked-up vessels. Thus, in a remarkable case, observed by Dr. Todd (Med. Chir. Trans., vol. xxvii.,) where the innominate and the renal arteries were mainly obstructed, very singular cerebral symptoms and suppression of urine marked the event.

The obstruction to the current, offered by the prominent and ragged lining membrane in the site of its ruptures, gives rise to blowing systolic murmur, which, if seated near the heart, may be mistaken for that of constrictive disease of the aortic orifice. If a main bronchus were pressed on, there would be sudden deficiency of breathing, with clear percussion-sound.

Were the practitioner fortunate enough (guided by the sudden supervention of symptoms of the three classes now distinguished, and of a strong arterial murmur in a person known to have previously been free from this physical sign,) to divine the occurrence of acute separation of the coats of the aorta, it does not appear, that, in the present state of knowledge, the treatment would be materially improved by his sagacity. Did he fail to diagnose the occurrence, his aim would be to recover the patient-from the first shock of the accident, control excited arterial action, and relieve symptoms as they arose. And it does not appear that art could do more than this, were the anatomical nature of the affection understood from the first.

APPENDIX.

Vide pp. 38 and 39.

The observation of a considerable number of female children, between the ages of four and ten, who had never worn stays, leads me to the conclusion that, independently of any extraneous influence, there is proportionally more infra-clavicular movement in the female than in the male. But indubitably the main source of the excess of infra-clavicular movement in the adult female is due to the use of apparatuses interfering with inferior costal and phrenic action. The male dog breathes exactly like the human male, almost wholly with the abdomen, the chest rising inferiorly after the abdomen; the action in the female dog is very closely the

same.

Vide P. 43.

Although convergence of the upper ribs during inspiration cannot be established clinically, I do not mean to contest its reality. On the contrary, I have found, by performing artificial respiration after the removal of the integuments, on the dead subject, that the upper ribs do actually converge during that movement. The amount of approximation, even in persons with wide intercostal spaces, appears to me not to exceed one-sixteenth or one-twelfth of an inch at the outer edge of the costal cartilages.

Vide p. 48.

Mr. Henry Thompson, of University College, has recently suggested a very simple addition to the tape-measure described in the text, whereby the absolute and relative expansions of the two sides of the chest may be ascertained during one and the same respira. tion. The more ordinary plan requires two, and as no two respirations are probably precisely equal, Mr. Thompson's instrument (which may be had of Coxeter, Grafton Street,) obviates a source of fallacy.