The body is a machine constructed for the purpose of working. The kinds of work which the body of a man or woman does are many. Every act of perception or sensation, is an act of work; so is every thought, every emotion, every volition. The action of the heart or lungs in the circulation and respiration, the evolution of the animal heat, the various functions of secretion and excretion, digestion, motion, speech, etc., are all so many kinds of work. Now as regards work, it is well known that for its due performance force is required, and it is equally well known that for the development of force, matter that can be metamorphosed is necessary. The engine may be perfect, the water may be in the boiler, but unless there be force in the form of heat there will be no steam; and there will be no heat unless there be fuel in a state of combustion.
The human body differs from any other machine in the fact that it uses its fuel in great part indirectly; only in fact after it has been assimilated and converted into tissues of various kinds. Thus when a muscle contracts, it is the muscle itself which is consumed; when a thought is conceived it is the brain which provides the force; when an emotion is experienced, it is again the brain which is decomposed. The body, therefore, lives by the death of its own substance. It is true, some kinds of food such as alcohol, tea and coffee, and perhaps some others do not require to go farther than the blood to be burned, but these are mainly heat-producing, and not tissue-producing substances. But whether matter be consumed directly or indirectly, all bodily force results from its decomposition, and without this destruction of matter the body would be absolutely incapable of a single functional action of any kind whatever, and its temperature like that of the so-called cold-blooded animals would be that of the surrounding medium, the atmosphere.
The quantity of food required by the system varies like the demands of other machines in accordance with the amount of work which is to be performed. A plowman, other things being equal, consumes more than a watchmaker; just as a locomotive burns more fuel than the little engine that runs a sewing machine; the strong able-bodied active man, one who works his brains and muscles up to their full power, eats more than the weak, emaciated and inactive girl, who passes all her time in the recumbent position in bed; and the latter will, other things being equal, endure for a longer period entire abstinence from food. A little food with such a one goes a great way, the demands of the system are at their minimum, and hence a mouthful of bread, or a little tea and toast taken at long intervals, suffices for the supply of all, or a great portion of the waste of the body. With such a person there is not much intense thought, there is little or no muscular action, the pulsations of the heart do not require to be of much force, the respiration is feeble, digestion is at its lowest point, there are no great demands for animal heat, and in fact if the temperature of the atmosphere of the room in which such a person lies, be kept high, the function of calorification may be almost nothing. Still there must be some food taken. The body, can to a certain extent, be used up in supplying the force required for the several functions without the necessity for an immediate restoration of its tissues, but there is a limit to this, beyond which it is certain death to go.
Chossat[15] has determined this point very accurately by many experiments performed upon doves, pigeons, Guinea pigs, rabbits, etc. He found that as a mean result, death ensued when the body lost four-tenths of its original weight. For instance, a body weighing one hundred pounds, could endure the loss of forty pounds without death necessarily following. Five-tenths or one-half appeared to be the extreme loss of weight in inanition which the body could endure without death resulting.
In addition to the loss of weight the temperature fell rapidly, the action of the heart was lessened, the number and depth of the respirations was diminished, and the excretions gradually became smaller in amount.
Experiments such as those of Chossat on the lower animals, cannot of course be instituted on the human subject, nevertheless nature sometimes performs experiments for us which are not without valuable results; and accidents of various kinds, have also given us important data.
On the 19th of March, 1755, twenty-two persons living in the Alpine village of Bergemoletto, in Piedmont, were buried in their houses by an avalanche or whirlwind of snow. The space covered was about two hundred and seventy feet in length, sixty in breadth, and the snow was over forty-two feet in depth. Notwithstanding all the efforts made by the survivors it was impossible to extricate the buried persons till the 18th of April following. All were dead except three women, who, having found some hay, fed a goat with it, and thus obtained from this animal a pint of milk daily, on which they had managed to sustain life for a month.[16]
In Belgium in the year 1683, four colliers were confined in a coal pit for twenty-four days without anything to eat. On the twenty-fifth day they were taken out. In all that time they had lived on nothing but a little water, which flowed from the walls of the prison in which they were immured.[17]
A case is mentioned by Foderé[18] on the authority of M. Chaussier, in which some workmen were taken out alive after having been confined for fourteen days in a cold damp vault. When released at the end of the time mentioned, their pulses were slow and weak, their animal heat greatly reduced, and respiration barely perceptible. Foderé ascribes their long existence without either food or drink, to the fact that the atmosphere of the vault was exceedingly humid, and that the moisture was absorbed into their bodies, taking the place of water ingested into the stomach.