To this class belong the following: a. The contraction and subsequent atrophy which affect the arteries of organs that are becoming atrophied through accidental or intentional (operative) injuries inflicted on portions of the body which have been previously arrested in their growth.

b. An obliteration which is very similar to the atrophy of the foetal passages, as for instance, that of the Ductus arteriosus. Such an obliteration of an artery is occasioned by the establishment of a collateral circulation, which is especially induced by a congenital narrowness (obstruction) of the artery in question. The vessel becomes narrower in proportion to the progressive development of this collateral circulation, and is entirely closed when the latter is completed. To this class undoubtedly belong many cases of obliteration of the different arteries, the causes of which have not been sufficiently explained, and most certainly those cases of obliteration of the aorta at its arch beyond the part where the Ramus brachiocephalicus is given off, corresponding to the depression of the Ductus Botalli.

These cases, which embrace the majority of the observations made on obliteration of the aorta, have hitherto been unexplained, both in reference to the malformations on which they depend and the process giving rise to final obliteration. They have been repeatedly collected and arranged (Barth, Craigie).

From the interest which attaches to these obliterations of the aorta we are induced to add the following remarks, which are derived from the observations above referred to, as well as from my own experience.

1. An inconsiderable portion of the arch of the aorta, generally at the part already referred to, becomes sooner or later obliterated. The aorta, that is to say its descending portion, is generally abnormally narrow before the establishment of complete obliteration.

2. The aorta before this point, and the branches given off from its arch exhibit considerable dilatation, which extends from these branches over all their ramifications and anastomoses.

3. The heart is in a state of general dilatation, although the left ventricle is the special and original seat of the affection, which also extends to the trunk of the pulmonary artery and its branches.

A careful consideration of all the circumstances leaves little doubt that the following theory is correct.

1. This anomaly is based upon a deficient formation, consisting in the permanence of the aorta in that early foetal condition in which it constitutes a trunk which merely supplies branches to the head and upper extremities, whilst the pulmonary artery bends round towards the descending aorta in the form of the future Ductus arteriosus, and supplies branches to the rest of the body. The ascending aorta, after giving off its three branches, merges as a thinner vessel into the pulmonary artery. If the branch of the pulmonary artery which bends down to the descending aorta, and represents the Ductus arteriosus, be closed, - which, singularly enough, happens in all cases, - the descending aorta cut off from the pulmonary artery, approaches the ascending aorta so closely as to leave only a very narrow connecting link between them, viz., the thin vessel already described, merging into the pulmonary artery which represents the descending aorta.

2. This portion of the vessel, from its narrowness, presents the conditions requisite for its obliteration and atrophy. It becomes narrower, with increasing years, in relation to the ascending aorta and to the quantity of blood passing through that vessel, while, at the same time, not only the ascending aorta, but the branches given off from it are proportionally dilated. This dilatation soon extends over all the ramifications and their anastomoses, as, for instance, those of the internal mammary and the first intercostal with the remaining intercostal and the epigastric arteries. In proportion as the collateral circulation draws the blood more freely from the left side of the heart and from the isthmus between the arch and the descending aorta, the former becomes narrower, and is at length rendered useless, completely closed, and finally atrophied.

The heart is, in all these cases, more or less distinctly affected with active dilatation. This dilatation obviously depends at first on the narrow isthmus between the ascending and descending branches of the aorta, and, after the latter has become atrophied, on the inefficiency of the collateral circulation.

This contraction and closure of the aorta has been observed from the fourteenth to the ninety-second year. It occurs far more frequently in men than in women. There are fifteen or sixteen such cases on record.1

1 These cases, as already remarked, were collected by Barth (Presse Médicale, 1837), and by Craigie (Edinburgh Med. and Surg. Jour., Oct. 1841). Craigie enumerates ten cases,' among which, according to Hasse's statement (Path. Anatomie, Bd. i. p. 91), one of the cases collected by Barth must be wanting. I unfortunately have not Barth's memoir by me at the present moment. He collected nine cases, which include Otto's case (which Hasse must have missed in Barth's collection, as he specially enumerates it, although it is not given in Craigie's list), Römer's case (Oest. Jahrb., Bd. xx. St. 2), and the case observed by Craigie, and described in the above-named memoir. These, together, make twelve cases, to which four others have been recently added - one case observed by M. Aug. Mercer in the year 1838 (which Craigie has overlooked), a case observed by Muriel in 1842, one described by Hamernjk in 1843, and one case, also occurring in 1843, which is preserved in our Pathological Museum.

We think that a more detailed notice of the last-named cases may contribute to the completion and elucidation of Barth's and Craigie's series.

The thirteenth case, observed by M. Aug Mercer (Bulletin de la Société Anatomique de Paris, xiv. année, p. 158):