such cases, in which medication by exercise needs much tact, and a profound study of each exercise performed. Here we shall only formulate this law:

The muscular work being equal, the sensation of fatigue is the more intense, the more active the intervention of the cerebral faculties demanded by the exercise.

Consequently, in dealing with very nervous persons, it will be necessary to employ exercises which do not need a sustained attention, those of which the movements are easy, and as much as possible, automatic; walking, for instance.

CHAPTER II.

BREATHLESSNESS.

A Hard Run-Exercises which cause Loss of Breath; Trotting and Galloping; Going Upstairs-Law of BreathlessnessRespiratory Need; Conditions under which it Increases and Diminishes-Carbonic Acid; its Production Increases with Muscular Activity; it Diminishes during Repose-The Sleep of the Marmot-Explanation of the Law of BreathlessnessWhy we lose Breath in Running-Why the Horse Gallops with its Lungs-Why Exercises of the Legs cause more Loss of Breath than those of the Arms--The Coefficient of Breathlessness-The Horse which exceeds its Paces-Breathlessness is an Auto-Intoxication by Carbonic Acid-Analogy with Asphyxia--Impossibility of Fighting against Breathlessness.

HAVE you ever found yourself within sight of the station and been afraid of missing the train? You have a quarter of a mile to traverse, and you see from your watch that you have only two minutes. You will have to run, and for years you have been accustomed to the measured pace of the man who walks when he has plenty of time and takes a cab when he has not. But you want to catch that train, and plucking up courage you set off as hard as you can run.

Your legs are strong and it does not hurt them when you run. However, after a few seconds, a peculiar distress seizes you. Your breathing is embarrassed, a weight seems to press you down, and a bar to be fixed on your chest. Your respiratory movements become jerky and irregular. With each step distress increases and becomes more general. Your temples throb violently, an insupportable heat rises to your brain, an iron band is tied round your forehead. Then there is a singing in your ears, your sight is disturbed, and you

have but a confused idea of the objects you pass, and of the people who turn to stare at your pale and dishevelled figure.

You reach your goal. As the train whistles you sink exhausted on the cushions of your compartment. There, in spite of the satisfaction of having caught your train, and the solace of being seated, your distress continues. Still for some minutes you are out of breath, and the hurried movements of your chest make you resemble a man seized with a violent attack of asthma. This is what we call "being winded."

We are seldom astonished by things which we see every day, and it seems natural to every one that a man should be out of breath when he has been running. But if we think about the matter, there is something surprising in the phenomenon of breathlessness while running when we run the legs do the work and the lungs become fatigued.

I.

No methodical exposition and rational explanation of breathlessness have hitherto been given. This form of fatigue has not as yet been the subject of any monograph; it is not described in any great dictionary of medicine nor in any physiological text-book.

There is however, no phenomenon more common and more frequently observed than breathlessness; there is none more interesting from the point of view of the hygienic and therapeutical results of muscular exercise.

Breathlessness is a feeling of distress which is produced during violent exercise or intense muscular work, and it is characterised by an exaggeration of the respiratory need, and by profound disturbance in the functions of the respiratory organs. This state is merely a peculiar form of dyspnoea and presents the general phenomena due to deficient aeration of the blood. But it differs from the respiratory troubles which we notice in morbid conditions by certain special signs which we shall point out, and above all in the conditions in which it is produced and in the mechanism of its production.

If we try to determine in what conditions breathlessness is produced during work, we are struck first by the fact that certain exercises, certain movements, seem to have the privilege of influencing more promptly than others, the respiratory functions.

In certain muscular actions fatigue takes the form of breathlessness, and respiratory distress forces the individual to stop working long before the muscles are fatigued. A man running, or rapidly going up-stairs, is forced to stop, not to rest his legs, but to take breath.

In other exercises, on the other hand, the muscles are fatigued and refuse to go on working long before breathlessness occurs. Going along a hanging ladder by the hands only, dumb-bell exercise, holding out weights at arms' length, are movements which quickly fatigue the limbs without causing any marked disturbance in the respiratory functions. When we are obliged to stop these exercises it is not because we are short of breath, but because our muscular force is expended.

In animals it has been noticed that certain paces, certain forms of work, more particularly produce breathlessness, while others rather produce fatigue of the limbs.

Trainers say, "A horse trots with its legs and gallops with its lungs." This phrase expresses well, with its humorous figure, the importance of pace in the production of breathlessness. Why is a horse more out of breath after a gallop than after a trot? Our first idea is to attribute the more prompt breathlessness to greater swiftness. But we must not confound pace with speed. The pace of galloping is not incompatible with very little speed. We can slow down the gallop of a horse till it falls behind another horse which is trotting. There are animals so awkward that their gallop is as slow as a walk. Now, however slow a gallop may be, it will more quickly make a horse out of breath than an equally rapid

trot.

Breathlessness is not then produced under the same conditions as local muscular fatigue, and certain exercises seem to have the privilege of influencing respiration.

When we try to find the explanation of this fact, we

naturally ask at the outset whether the exercises which cause loss of breath have not a direct influence on the organs which execute the respiratory movements, whether they do not require, for example, that the muscles of the chest and back should be involved, the contraction of these muscles interfering with the action of the ribs. But this hypothesis is discredited at the first glance, for the exercises which in man cause most breathlessness are not those which demand work from the upper limbs, and consequently the direct concurrence of the thoracic muscles. Running, leaping, going up a steep ascent, are, of all known exercises, those which most quickly cause loss of breath, and they are executed by the legs, the muscles of which are not attached above the pelvis, and have consequently no direct action on the thorax.

We believe it to be impossible to explain the tendency of this or that muscular exercise to produce breathlessness, if we direct our attention solely to the peculiarities of movement and attitude which these exercises render necessary.

Certain authors, who have incidentally referred to breathlessness, seem to attribute this form of fatigue to the very mechanism of the exercises which cause it, and to the direct disturbance which these exercises produce in the respiratory movements.

Breathlessness in running occurs because the runner, unable to make the deep and prolonged inspirations necessary for the continuance of his efforts, endeavours to make up for this by frequency of respiratory movements, so that he can fix as firmly as possible his vertebral column and his thorax.” *

We quote this opinion to show how, as a rule, authors who have written about muscular exercise have made what seemed to them reasonable deductions, rather than direct observation of facts. In fact, Michel Lévy's view is based upon an error of observation which anyone can verify personally if he is not afraid to run for a minute. or two. In a man running it is not inspiration which is difficult, it is expiration. In this exercise we experience Michel Lévy. Traité d'hygiène.