Such are the principal natural influences which individually or in different combinations threaten or assail the sound heart and blood vessels after the age of 40. I have given but a broad, hasty sketch of them entirely from my own recent observations, and I know that I have omitted some which in your opinion might deserve mention, but which possess no special interest in relation to this period of life--for example, the agents of acute infections of the endocardium, and also new growths, pregnancy and parturition. Let me now sum up the results, and say that whatever changes the cardio-vascular system may present in middle and advanced life, beyond those which we have found to be natural to it at those particular periods, are pathological--the result of physical stress, nervous influences, extrinsic poisons, disturbances of metabolism, syphilis, acute disease, or chronic disease; or are associated with chronic nephritis, emphysema or different combinations of the preceding causes, with various occupations or positions in life, or with other influences of less importance. It is necessary, however, to qualify this statement in two respects. In the first place, the heart and vessels may have been so damaged already, that is, in early life, that they fall victims to influences which, whether in kind or in degree, would have been insufficient to produce idiopathic disease of these organs. This brings me to the subject of old-standing valvular disease (mostly rheumatic in origin), chronic strain, and adherent pericardium in middle-aged and old subjects. A considerable proportion of our cases are of this type, and they have to be mentioned here for the sake of giving completeness to the plan of arrangement, but they are outside the range of our immediate subject. In the second place, hearts and arteries at 40 that appear to the naked eye free from damage may be molecularly weak, and unable to offer effective resistance even to influences of an every-day character. I have now arrived at the last, and certainly one of the most interesting, of the causes of disease of the heart and arteries in middle and advanced life. There are some persons whose hearts and arteries cannot carry them through the wear and tear of what may be called ordinary life for more than 40 or 50 years. The vital energy of the tissues of these organs is exhausted prematurely; they are already old at 45; degeneration of the muscle and other cells sets in early, reminding us of the essential myopathic paralysis of children. This type of case is described as "family heart," for it also runs in families--three, four, five, or more members of which, as in a number of instances that I have observed, may have all died suddenly of cardiac disease--some of them at an early age. Similarly, it is not by any means unusual to find quite young subjects, say of 30, with vessels already much enlarged; and I may add, equally young subjects with their lungs