"The two diseases, aneurism of the aorta and inadequacy of the valves, may, however, be combined. Aneurism of the ascending aorta may, by extending to the mouth of this vessel, dilate it so that the valves are unable to meet, and there is then a combination of the two diseases; there is aneurism and there is permanent patency of the aortic opening. The first cases that came under my observations presenting the signs of inadequacy of the aortic valves were cases in which the valves were rendered useless in this way, namely, by the mouth of the aorta sharing in the aneurismal dilatation. These cases led me into an error; for, meeting the signs of permanent patency of the aortic orifice in conjunction with aneurism, I erroneously attributed to the aneurism the signs which arose from the permanent patency. Aneurism of the aorta of itself does not produce the signs arising from permanent patency of the mouth of the aorta. It can only produce them in the way already described, by involving in the dilatation the mouth of the aorta; and hence, when in conjunction with an aneurismal tumor of the arteria innominata or aorta, there are found visible pulsation, _bruit de soufflet_, and _frémissement_ in the ascending aorta, and the trunks arising from it, we may be certain that, in addition to the aneurism, there is a defect in the aortic valves, or that the aneurism has extended downward, involving the mouth of the aorta. On the other hand, if these signs be absent, the valves are sound and the mouth of the aorta is not included in the disease. The propriety of performing Mr. Wardrop's or indeed the common operation for aneurism about the neck might depend on the information {205} thus obtained of the state of the aortic valves. To perform either in a case where the aneurismal dilatation was so extensive as to involve the mouth of the aorta, or where the aortic valves were diseased, would only bring the surgical treatment of the disease into unmerited discredit." Another very distinct contribution of Corrigan to the medicine of his time was his insistence on the distinction that exists between typhoid and typhus fever. This is one of the most interesting features of his little book on the _Nature and Treatment of Fever_. With our present knowledge, it seems hard to understand that these two fevers should have been so long confounded, but as a matter of fact it was not until the middle of the nineteenth century that the distinction between them was recognized even by the most acute observers. In this matter the French and Americans anticipated most of the rest of the world, though Corrigan's teaching in the matter had been correct for many years before others in the British Isles came to the true position.