In spite of this result, so unfavourable to the cooling of the blood, the body, in a state of rest, can easily defend itself from invasion by external heat, thanks to the cooling produced by the evaporation of sweat from the skin, and the transpiration of vapour by the lungs; it is for this reason that it is possible, without any serious consequences, to spend some minutes in an oven, the temperature of which greatly exceeds that of the air in the hottest summer. But if to the action of the high temperature there is added that of muscular work, the organism has not only to fight against the heat of the surrounding medium, it has also to defend itself against the increased heat developed in its own organs. It is deprived, in this unequal contest, of the assistance of the vaso-motor apparatus, the action of which has become useless. The blood, constantly carried to the skin, can no longer lose heat by radiation in a medium already hotter than itself, and returns to the internal organs, carrying with it almost all the heat produced by work.

There is a very clear distinction between our way of understanding sunstroke and that in which it is ordinarily explained. We do not believe that the sun kills a man by giving him more heat, but simply by preventing him from getting rid of the internal heat, which is being produced in excess. The practical importance of this distinction is at once evident. A man who succumbs during a forced march, under a hot sun, is not killed by the sun, but by the forced march. He does not die of sunstroke, but of overwork, and consequently if he were not overworked, the sun alone could not kill him. The sun is not the essential cause of the accident, it is merely an accessory condition.

In our temperate climates we never see cases of fatal sunstroke in men exposed to the heat of the sun, unless these men have been doing some fatiguing work. A man under the powerful sun of July may perhaps have a sunstroke, if his skin is delicate; he may have a congestion of the brain if his head-covering is not sufficient; he may suffer from very various disorders due to the excessive heat a fainting fit, an attack of indigestion, etc.,

but never from any fatal illness, unless there be complication with some other disease, or some constitutional vice, which will have no connection with sunstroke properly so called.

Cavalry officers know that their men are rarely attacked by sunstroke, while the horses which carry them often succumb to it. It is among the infantry that sunstroke is almost exclusively observed, especially in forced marches and when the men are heavily laden. The infantry officer, who carries no baggage, is much more rarely attacked than his men, and among the latter the so-called sunstroke always fixes on those who are least accustomed to fatigue. In the cases of sunstroke reported every year in connection with the great manœuvres, the soldiers who succumb are always reserve men who have passed without preparation from muscular inaction to excessive work, and are placed, in consequence, in the conditions most favourable for the production of overwork.

The same observations have been many times made as regards animals. It is a matter of common notoriety that horses are so much the more liable to sunstroke, the fatter they are, and the less trained by daily work.

Men inured to fatigue, those who daily do hard work, rarely suffer in the way we have just described. We never see in the country a peasant die of sunstroke. And yet no regiment performing manoeuvres ever supports the heat of the sun longer and with as much disregard of precaution as do the reapers.

To sum up, the heat of the sun cannot alone cause death, except in tropical climates. The cases of socalled sunstroke seen in our temperate countries are indeed due to an increase in the temperature of the blood, for a temperature of 112° F. has been noticed in dying persons; but this excessive temperature is not the result of the heat of the sun, it is a consequence of excessive vital combustion.

What kills a man in so-called sunstroke is overwork, from which he suffers in ill-understood hygienic conditions, but it is not the sun.

CHAPTER IX.

OVERWORK (concluded).

A Phthisical Hercules-The Overtrained Horse-Chronic Overwork-Exhaustion through using up of the Organic Tissues -Difference between the Physiological Processes of Acute and of Chronic Overwork-Auto-Intoxication and AutophagyDangers of excessive Expenditure-Defective Balance between Expenditure and Income-Impoverishment of the System by excessive work-Atrophy and Degeneration of Muscles-The Calves of Runners-Overwork of the Heart-Muscle-The Over-Driven Heart-Nervous Forms of Overwork-Anæmia of the Nerve-Centres and Exhaustion of the Nervous Substance -Epilepsy of Walkers-Observations on Peasants-Insanity from Overwork; Influence of Harvest-Time on its FrequencyFrequency of Neuroses in Overworked Peasants.

ONE day, passing before a booth of acrobats, we were struck by the sickly appearance of a man who was haranguing the crowd, and all the while juggling with cannon-balls and dumb-bells. He was a great, rawboned fellow, with a starved appearance, drawn features, long and slender limbs, but none the less seeming to have great muscular strength, to judge from the ease with which he handled his weights.

The booth was a wretched one, and the spectators far from choice, but the desire of seeing at work this Hercules of phthisical build overcame our self-respect, and going up the inclined plank which took the place of a staircase, we entered the establishment.

Then we could see the man more closely and assure ourselves that his limbs, in spite of the strength shown by his performances, were thin and fleshless. His thin thighs, which worked wonders in French boxing, no longer filled his tights, which fell in numerous folds. Finally a weak and hoarse voice, with a few fits of

coughing, made us believe that this strong man had an extremely delicate chest.

When the performance was over, we found it easy to become initiated into the mode of life of this man who seemed to us an interesting case for study. Hurrying from fair to fair he worked excessively hard, giving ten performances a day, in each of which he had to throw one or two opponents, not to speak of single-stick, French boxing, and juggling with weights and dumbbells. His muscles were rarely idle, but they did not increase in size, far from it. It is true that his diet was not fattening, and he only dined well when the takings were good. The strong man, becoming more confiding, spoke to us about his health, and we could easily understand that he was phthisical. In fact, shortly afterwards we heard that he had fallen a victim to pulmonary phthisis.

Such is often the end of strong men, who, beginning by mastering fatigue, after going through a training which enables them to work to excess without feeling the discomfort of fatigue, exceed the limit of their strength, and do not repair their loss by substantial diet.

Trainers have a very striking expression when they wish to describe a horse which has been overtrained; they say that the horse has become stale, this means that the excessive work it has undergone has consumed not only the reserve materials, fats and other substances not directly concerned in movement, but the combustions have attacked the horse itself considered as a machine, and its muscular tissues, the essential motor organs.

Similarly our Hercules at the fair had been used up by excessive muscular work. He offered a type of a kind of overwork very different from that we have previously described, and which we shall call organic exhaustion.

I.

The form of overwork which we call organic exhaustion is a condition of chronic fatigue in which the organism, instead of absorbing the noxious products as

in acute fatigue or febrile overwork, is despoiled of its useful materials and of the tissues most necessary for life.

This condition represents usually the chronic form of fatigue, but it can come on very quickly when there is inanition as well as work. There results a defective balance between income and expenditure.

If a man performs violent exercise and his nutriment is proportioned to the work, the system can repair its losses; and the work having a tendency to distribute the assimilated materials to the organs which participate in the action, the muscles benefit from the excessive nutriment, and the machine becomes stronger. But if insufficient food is taken, or, what comes to the same thing, if the nutriment introduced into the stomach is not assimilated, there is a disproportion between the expenditure of heat demanded by the animal machine, and the quantity of fuel supplied to it from without. Now movement cannot occur without heat, and heat cannot be produced without combustible materials. Thus, in default of sufficient food, when the reserve materials have been consumed the essential organs of life have to serve as fuel. A man who eats little and works much may be compared to those unfortunates who, having exhausted all their fuel, make up for it by burning the remains of their furniture.

It is not always a profession demanding great muscular force which leads to organic exhaustion. It is rather an occupation needing a great many hours of work. The combustions are not in this case very violent, and there is time for the elimination of the waste-products formed by them: the products of dissimilation do not accumulate in the system, there is no auto-intoxication, but many organic substances are burned, and the body suffers.

It may happen that a man becomes exhausted without experiencing the slightest discomfort from fatigue, and may go on with his work, steadily losing weight. But when the system is deprived of some of its essential materials, he falls into a condition of "diminished resist

" and can no longer defend himself against the