With regard to the effects on the heart of exercise, when it is taken to preserve or improve the health, or even in the case of those who carry it beyond this point, though still within the bounds of amateur sport, it is not easy to make a decided statement. The reports are conflicting, some authorities appearing to have seen a great many evil results from athletic sports, effecting the heart, while others are of the opinion that their injurious influences have been much overrated. To begin with, not all who enter athletic sports have their hearts examined, and even when they do, it is very seldom that a physician is thoroughly satisfied with the examination he has made. But let us suppose our athlete has a sound heart. Let him be well fed with the proper kind of food, and be supplied with the proper kind of air; let his sleep be enough in quantity, and taken at the right time, his habits such as are conducive to health, especially as regards the use of tobacco and alcohol. These things being so, what is the effect of exercise on the heart? As the heart affects, and is affected by the whole body, it cannot be taken strictly by itself, nor would such a plan be wise. The first effect of exercise on the heart is to increase the number of its pulsations, and the force of each individual one. As a consequence, the flow of blood through the body is increased, including the heart itself, and the waste of the system is washed out more completely and a large supply of fresh material is borne to all parts. While the exercise is within any reasonable bounds, the heart beats increase some twenty or thirty a minute over what they are when the person is at rest; in spite of this increase in number, the character of the beats is regular and even. When the labor is excessive the heart will become tired, the pulsations very rapid, but feeble, and unless exertion is brought to an end mischief will follow. Disease of the blood vessel is, however, of rare occurrence in early life, and any young man who is so affected should never for one instant think of subjecting himself to violent athletic sports. By a common and silent consent, the objection to active exercise passes over the ordinary ill received, and fixes itself almost entirely on one organ, the heart, and there, on almost one malady alone, hypertrophy, the overgrowth of the muscular substance. That this disease can arise from physical exercise there can be no doubt. That it does frequently thus arise in healthy persons, I do not believe. In a long experience I have seen scarcely one case of organic disease of the heart which can be traced to amateur athletic sport, pure and simple, that is, if the man was healthy originally. The increased work in which the hypertrophy arises is probably in part the result of the increased frequency and force with which, in consequence of the respirating needs, the heart acts. But it is in part the result of the compression of the capillaries of the muscles by the contracting fibres, and also the result of the compression of the arterial trunks by the rigid muscles. The total resistance to the action of the heart is thereby considerably increased. From carefully compiled statistics of the English University crews, not only are the men not injured, but actually improved in health, if we may judge from the fact that their years are increased. But length of days is not everything. Ruined health from a diseased heart may make a man sigh for death. Here, again, the figures are most favorable, for a smaller percentage of these men died from heart disease than is found among average men.

We have seen that oxygen for the most part is taken in through the lungs, and the act which they perform taking it in is called respiration. At the back of the mouth are two passages leading downward, the one in front going to the lungs. The act of breathing requires that this trachea, as it is called, should be kept open all the time, so there are placed in its walls rings of cartilage which are incomplete in some part of their circumference. The epiglottis, fastened to the back part of the tongue keeps food from falling into the windpipe when we are eating. After the windpipe has gone down into the chest it divides into two parts, and goes to the right and left sides. Each of these enters the lung on its own side, and then splits up into a number of smaller branches. The smallest bronchial tubes at last end in little sacs which are air cells. The walls between them are very thin, and in these walls are the capillary vessels into which the artery bringing the blood from the right side of the heart breaks up. So the blood flowing through them is exposed to the air on both sides. In early life the lungs have a rose color; but as a person grows older, a quantity of black looking matter is found scattered through them, and sometimes forming streaks in the surface. This is shown to be corbon, and has been inhaled from time to time. Inhaling certain kinds of dust will give pulmonary consumption.