1. In relation to its use as a definite remedial measure in a few pathologic conditions.

2. In relation to the development of the individual in structure and function.

3. In relation to general somatic vigor. Somatic vigor is the essence of that power of resistance which the organism shows to the invasion of disease. It is well known that the power of resistance varies much in the individual from time to time; pathogenic bacteria will at one time be destroyed promptly, while at another they will gain a foothold and multiply.

Disease must be avoided by the prevention of inoculation; but, what is of equal importance, it must be averted by the maintenance of such bodily vigor that the maximum of resistance will be offered by the organism itself. Special Considerations - the physician has three questions to answer about muscular exercise :

1 . What specific exercises will be effective in given pathologic states? Under this head I discuss nothing here. It is my province to examine the general effects of exercise together with the detailed effects of specific exercises and sports.

2. What character and quantity of exercise are needed for the growing organism, to ensure balanced development? Physicians must pass upon the claims of various systems of gymnastics that are offered for adoption by schools, as well as upon the necessity for, and the character of, work outside of school. It is hoped that the data given will be sufficient for full and intelligent answers to these questions.

3. What exercises are best adapted under various conditions, such as age, sex, and the like, to render most active the general somatic life of the individual? This question I hope to answer with some degree of definiteness.

I am aware that some of the more important conclusions here set forth are not in accord with the accepted doctrines of many teachers of physical training; yet these views will be seen to have their justification both in clinical experience and in biologic science. While I shall in the main confine my work to conclusions and their practical application, certain preliminary considerations need to be stated, to form a rational basis for the practical directions that follow.

Those conditions under which the body was given its present size, shape, and structure are in general the conditions adapted to maintaining the fullest functional activity. During the unnumbered years of evolutionary time, muscular exercise in labor, war, or the chase has been one of the major elements of human experience. Upon neuromuscular ability the race has depended for survival, even when its ancestors were in a condition of development yet more elementary than that of savage life.

A biologist, having brought to him a human body and being asked for a statement of its functions from an examination of the structure, would say that both in form and function the organism must have been adapted to a life of considerable muscular exertion; that this appeared, first, from the proportions of the muscular system; that the lungs as well as the heart indicated far more capacity than would be needed for a life exclusively or even largely sedentary; and, finally, that the nervous system was designed predominantly.

The initiation or control of muscular movements.

The health of such an organism depends upon the balanced cooperation of all its parts. These parts have become adjusted to a certain general balance in the activities of the nutritive, neural, and muscular tissues.

No argument is necessary to the evolutionist to show that the necessity for muscular exercise has been constant and predominant throughout the whole history of the life of the species; that it has been so constant and so large a factor in adjustment to the total environment as to have had a chief share in determining the character of the organism itself; and that those conditions which have been decisive in determining the form and functions of the organism are the conditions in which it functionates the best.

The argument for muscular exercise from the standpoint of evolution is thus the strongest that can be presented. The environment of the organism cannot be changed in other respects with impunity. Man has become adapted to breathing air of a certain approximate constitution, and he is at his best in this environment.

He has become measurably able to carry his environment with him with reference, for instance, to temperature, and somewhat with reference to light; but the general fact remains that perfect adaptation to environment is most definitely related to health.