classes have need of supplementary respirations to compensate for the insufficiency of the respiratory field which has been reduced by the disease, sometimes by as much as half. Exercises of endurance constitute in such cases a valuable means of treatment. They make it possible, through increasing by a very little at a time the carbonic acid formed by work, that the whole of this excess shall be eliminated at each expiration, there being in exchange a small excess of oxygen introduced during inspiration. If the exercise is well regulated it can be kept up for hours, and the patient will then have benefited without incurring the dangers of breathlessness, from a series of small quantities of oxygen the sum total of which will be equal to that gained by a healthy man in an exercise of strength or of speed. Referring to the calculation made above, we see that moderate exercise, like walking, kept up for four hours, makes a man absorb as much supplemental oxygen as a most violent exercise, such as running, does in an hour.

Generally we do not make use enough of exercises of endurance in treating patients with lung trouble. We should boldly prescribe for tubercular or asthmatic patients long walks on level ground, or sustained exercise at the oar, coming down stream and rowing with a very slow stroke.

Respiration is the most important of the functions influenced by exercise, but it is not the only one to be considered in exercises of endurance. The respiratory function is for the elimination of carbonic acid and of many other substances resulting from the combustions of work, but all the products of combustion are not eliminated by the lungs.

The fractional performance of work, which lends itself so well to the regular expulsion of carbonic acid, has not the same influence on the elimination of the other products of dissimilation, on the waste-products found in the urine for instance. .If we refer to the chapter

dealing with the urinary deposits which occur after work, we shall easily understand that the fractional performance of the work cannot hinder the accumulation of the products of combustion which are eliminated by the urine, because this elimination is a slow process. The carbonic acid formed during work is immediately eliminated by the lungs; the sparingly soluble compounds resulting from muscular waste are not found in the urine for at least three hours after the muscular work which has led to their production. If the slowness of the work can retard the time when these wasteproducts will accumulate, their accumulation is none the less inevitable, for in an exercise which has lasted three hours, the work will be finished before the system has got rid of any particle of these waste-products.

This is why an exercise of endurance, if it may retard the onset of fatigue, cannot save the system from its consequences.

Here is, moreover, a remarkable confirmation of our theory of stiffness. We believe that the stiffness of fatigue is due to an overcharge of the blood with urates, a kind of transient uricemia, just as breathlessness, another form of fatigue, is due to the presence of an excessive quantity of carbonic acid in the blood. A man who, not being in training, goes out for a day's shooting, will inevitably suffer on the following day from a more or less severe attack of stiffness, and yet his exercise, the type of an exercise of endurance, will not have produced breathlessness at any time during the day.

These observations give us the key to a fact which is at first sight very surprising, and even inexplicable except on our theory, namely that young persons support better exercises of speed than exercises of endurance.

A child of seven years old will bear very well all the games which need rapid and prolonged running. This is owing to the wonderful ease with which its lungs adapt themselves to the exigences of forced respiration. The carbonic acid produced by work is eliminated with great rapidity and causes no inconvenience to the system.

But carbonic acid is not the only product of dissimilation due to work which must be eliminated from the system, and there are others whose exit is slower, notably those resulting from the dissimilation of the nitrogenous tissues. Now dissimilation is much more rapid in the child than in the adult, for the young tissues have less stability than the adult tissues. Hence the formation of nitrogenous waste-products, of which uric acid and urates are the chief, is more abundant. Exercises of endurance which allow of the elimination of the whole excess of carbonic acid with each expiration, lead to no accumulation of this gas, but they can cause an accumulation of the nitrogenous waste-products, for the elimination of these does not begin, as we have shown, for three or four hours after the muscular work which has caused their formation.* An exercise may then be continued for four hours, and give rise throughout this time to the formation of nitrogenous waste-products, not one particle of which is being eliminated. All these waste-products will be accumulated in the blood when the exercise has come to an end. The system which will have escaped the effects of carbonic acid, a gas which is eliminated as fast as it is formed, will not escape those of nitrogenous waste-products which will have accumulated in large quantities in the blood. There will be after the exercise of endurance is over, a true uricæmia, a surcharge of the blood with uric acid compounds.

This result explains how it is that young persons who, thanks to the adaptive power of their respiratory organs, have borne with impunity an exercise of speed, and have not lost breath, can easily suffer from febrile stiffness, and even from febrile overwork, after too long a walk.

Gouty persons are, like children, exposed to the accidents of consecutive fatigue after exercises of endurance. They have already a constitutional tendency to the accumulation of uric acid in the blood, and muscular exercise causing the production of nitrogenous waste

* See above the chapter "Stiffness," p. 119.

products which cannot be eliminated as fast as they are formed, hence there is, when the long-continued work is over, an abundance of uric acid compounds in the blood. We know that an attack of gout is due to this uric saturation of the blood, and thus are explained the attacks of gout which, in gouty subjects, almost inevitably follow a very long day's shooting, when a man has not been prepared by gradual training, the salutary effects of which in preventing the formation of deposits of urates we have already studied.

To sum up, the exercises of endurance allow of the performance of such work with great economy of fatigue. They give the system the benefit of a supplementary acquisition of oxygen, without exposing it to the dangers of forced respiration. They quicken the circulation of the blood without fatiguing the heart or violently distending the vessels. In a word they spare the whole machine during work.

But if they preserve the system from the accidents of immediate fatigue, they do not save it from consecutive fatigue. If they enable it to escape breathlessness, this is not the case as regards stiffness.

Moderate and prolonged exercise, that in which the total work is considerable, but well-divided, is suitable for patients whose respiration needs management. It cannot be prescribed without preliminary training for gouty persons, and is absolutely unsuitable for children.

Exercises of speed are well suited to young persons, who easily eliminate carbonic acid. Exercises of endurance are better suited to persons of ripe age, whose nitrogenous tissues resist better the processes of dissimilation, and form less the nitrogenous waste-products. Conscripts are excellent for manoeuvres of speed, and veterans for manœuvres of endurance.

CHAPTER VI.

MECHANISM OF DIFFERENT EXERCISES.

The Principal Action and the Indirect Actions in Exercise-Part Played by each Part of the Body in the Chief Exercises-Office of the Upper Limbs-Gymnastic Apparatus: especially bring the Arms into Action-Suspension and Support of the BodyBreasting and Circling in the Gymnasium-Rowing; Fencing; Single-stick; English Boxing; Dumb-bells - Office of the Lower Limbs-Walking and Running; French Boxing or Chausson-Usefulness of Exercises of the Legs in developing the Chest-Office of the Pelvis-Flexion of Pelvis on Thorax in Gymnastic Exercises. Development thus given to the Abdominal Muscles-The best Girdle against Obesity Office of the Vertebral Column in Exercise - Importance of Position-The Horseman with a "Good Seat"-Active Share of the Vertebral Column in Exercise. Thrust from the Loins —Leaping-Passive Share of the Vertebral Column in Exercise -Orthopedic Effects of Attitudes of "Suspension "-Swedish Gymnastics.

I.

66

To understand the exact mechanism by the aid of which a given exercise is performed, we must discover what muscular groups are brought into action, and what bony levers are moved.

This analysis is not always easy, for besides the principal effort and most apparent movement, every exercise involves secondary efforts which associate in the work parts of the skeleton or regions of the body which we should not have expected to play any part. Different regions of the body may at one time have the chief, and at another only an indirect share in an exercise; and we see the arms, the legs, the head, the neck and the trunk, become in turn essential agents or accessory factors in a muscular action. But in general it is rare for an isolated region of the body to be exclusively charged with the work, and almost always