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of blood to the stomach the sensa- themselves in tubs of salt water, he tion of uneasiness is carried away. says. This would undoubtedly reHence we may conclude that Hunger lieve their thirst, but it is a plan is in some way dependent on the state which would be excessively dangerof the circulation in the stomach. ous in shipwrecks, unless food were abundant, since the abstraction of so much heat as would follow a bath would in all probability be fatal.
Thirst closely resembles Hunger in being a general or Systemic sensation, although it is usually considered only as a local and Organic sensation -the dryness of the mouth and throat. This dryness of the throat and mouth, so familiar to us all, is produced by a deficiency of liquid in the body; but it may be, and often is, produced when there is no deficiency in the general system, nothing but a local disturbance, this disturbance producing a local sensation. Wines, coffee, spices, &c., create a strong feeling of thirst, yet the two first increase the quantity of liquid instead of diminishing it. And we know how ineffectual liquid in any quantity is to quench the feeling of Thirst under some conditions, especially after long suffering.
Andersson, in his travels in Africa, describes the sufferings of his men and cattle, adding, "even when the thirsty men and animals were let loose in the water, although they drank to repletion, the water seemed to have lost its property, for our best endeavours to slake our thirst proved unavailing." "The long continuance of Thirst had produced a certain feverish condition which could not be immediately relieved when the system received its necessary supply of liquid; this shows that although deficiency of liquid is the primary cause of Thirst, the proximate cause must be some local affection which has been induced.
On the other hand, this local sensation is so dependent on the system, that if water be injected into the veins or the intestines, Thirst disappears, although the mouth and throat have not been touched. A humid atmosphere prevents Thirst; a bath relieves it, because the water is absorbed through the skin. On this principle, Franklin grounds his advice to men who are exposed to scarcity of drink: they should bathe
As deficiency of food to supply the waste of tissue is the primary cause of Hunger, so deficiency of water to supply the waste which goes on incessantly in the excretions, respiration, and perspiration, is the primary cause of Thirst. Every time we breathe we throw from our lungs a quantity of water in the form of vapour; and we are made sensible of this when the breath condenses on the colder surface of glass or steel, and when, as in winter, the atmosphere is sufficiently cold to condense the vapour on its issuing from our mouths. This is only one source of the waste of water: a more important source is that of perspiration, which in hot weather, or during violent exercise, causes the water to roll down our skins with obtrusive copiousness. But even when we are perfectly quiescent, the loss of water, although not obvious, is considerable. It is calculated that there are no less than twenty-eight miles of tubing on the surface of the human body, from which the water will escape as insensible perspiration; and although the amount of water which is thus evaporated from the surface must necessarily vary with the clothing, the activity, and even the peculiar constitution of the individual, an average estimate has been reached which shows that from two to three pounds of water are daily evaporated from the skin. From the lungs it is ascertained that every minute we throw off from four to seven grains of water, from the skin eleven grains. these must be added the quantity abstracted by the kidneys, a variable but important element in the sum.
It may not at first be clear to the reader why an abstraction of water daily should profoundly affect the organism unless an equivalent be restored. What can it matter that the
* ANDERSSON: Lake Ngami, p. 38.
body should lose a little water as vapour? Is water an essential part of the body? Is it indispensable to life? Not only is water an essential part of the body, it might be called the most essential, if pre-eminence could be given where all are indispensable. In quantity, water has an enormous preponderance over all other constituents: it forms 70 per cent of the whole weight! There is not a single tissue in the body-not even that of bone, not even the enamel of the teeth-into the composition of which water does not enter as a necessary ingredient. In some of the tissues, and those the most active, it forms the chief ingredient. In the nervous tissue 800 parts out of every 1000 are of water; in the lungs 830; in the pancreas 871; in the retina no less than 927. Commensurate with this anatomical preponderance, is the physiological importance of water. It is the carrier of the food, the vehicle of waste. It holds gases in solution, dissolves solids, gives every tissue its physical character, and is the indispensable condition of that ceaseless change of composition and decomposition on which the continuance of life depends. Such being the part played by water in the organism, we can understand how the oscillations of so important a fluid must necessarily bring with it oscillations in our feelings of comfort and discomfort, and how any unusual abstraction of it must produce that disturbance of the general system which is known under the name of Raging Thirst--a disturbance far more terrible than that of starvation, and for this reason: During abstinence from food, the organism can still live upon its own substance, which furnishes all the necessary material; but during abstinence from liquid, the organism has no such source of supply within itself. Men have been known to endure absolute privation of food for some weeks, but three days of absolute privation of drink (unless in a moist atmosphere) is perhaps the limit of endurance. Thirst is the most atrocious torture ever invented by Oriental tyrants. It is that which most effectually tames animals. Mr Astley,
when he had a refractory horse, always used thirst as the most effective power of coercion, giving a little water as the reward for every act of obedience. The histories of shipwreck paint fearful pictures of the sufferings endured from thirst; and one of the most appalling cases known is the celebrated imprisonment of one hundred and forty-six men in the Black Hole at Calcutta -a case frequently alluded to, but which must be cited here at some length on account of its physiological bearing:
The Governor of Fort-William at Calcutta, having imprisoned a merchant-the well-known Omychund, the infamous Nabob of Bengal, Surajah Dowlah, on the look-out for a pretext, marched against Fort-William with a considerable force, besieged and took it, and imprisoned the surviving part of the garrison in the barrack-room named the Black Hole. The letter in which Mr Holwell, the officer in command, describes the horrors of this imprisonment is printed in the Annual Register for 1758, and from it the following extracts are made :
hundred and forty-six wretches, exhaust"Figure to yourself the situation of a ed by continual fatigue and exhaustion, crammed together in a cube of eighteen feet, in a close sultry night in Bengal, shut up to the eastward and southward (the only quarters whence air could reach us) by dead walls, and by a wall and door to the north, open only to the westward by two windows strongly barred with iron, from which we could receive scarce any the least circulation of fresh air.
We had been but a few
minutes confined before every one fell into a perspiration so profuse, you can form no idea of it. This brought on a raging thirst, which increased in proportion as the body was drained of its moisture. Various expedients were thought of to give more room and air. To gain the former it was moved to put off their clothes; this was approved as a happy motion, and in a few moments every one was stripped-myself, Mr Court, and the two young gentlemen by me, excepted. For a little while they flattered themselves with having gained a mighty advantage; every hat was put in motion to gain a circulation of air, and Mr Baillie proposed that every man should sit down
on his hams. This expedient was several times put in practice, and at each time many of the poor creatures, whose natural strength was less than that of others, or who had been more exhausted, and could not immediately recover their legs when the word was given to risefell to rise no more, for they were instantly trod to death or suffocated. When the whole body sat down, they were so closely wedged together that they were obliged to use many efforts before they could get up again. Before nine o'clock every man's thirst grew intolerable, and respiration difficult. Efforts were made to force the door, but in vain. Many insults were used to the guard to provoke them to fire on us. For my own part, I hitherto felt little pain or uneasiness, but what resulted from my anxiety for the sufferings of those within. By keeping my face close between two of the bars I obtained air enough to give my lungs easy play, though my perspiration was excessive, and thirst commencing. At this period so strong a urinous volatile effluvia came from the prison that I was not able to turn my head that way for more than a few seconds at a time.
"Now everybody, except those situated in and near the windows, began to grow outrageous, and many delirious. Water! water! became the general cry. An old Jemmantdaar, taking pity on us, ordered the people to bring us some skins of water. This was what I dreaded. I foresaw it would prove the ruin of the small chance left us, and essayed many times to speak to him privately to forbid it being brought; but the clamour was so loud, it became impossible. The water appeared. Words cannot paint the universal agitation and raving the sight of it threw us into. I flattered myself that some, by preserving an equal temper of mind, might outlive the night; but now the reflection which gave me the greatest pain was, that I saw no possibility of one escaping to tell the dismal tale. Until the water came I had not myself suffered much from thirst, which instantly grew excessive. We had no means of conveying it into the prison but by hats forced through the bars; and thus myself, and Coles, and Scott supplied them as fast as possible. But those who have experienced intense thirst, or are acquainted with the cause and nature of this appetite, will be sufficiently sensible it could receive no more than a momentary alleviation: the cause still subsisted. Though we brought full hats through the bars, there ensued such vio
lent struggles and frequent contests to get it, that before it reached the lips of any one, there would be scarcely a small tea-cupful left in them. These supplies, like sprinkling water on fire, only seemed to feed the flame. Oh! my dear sir, how shall I give you a just conception of what I felt at the cries and cravings of those in the remoter parts of the prison, who could not entertain a probable hope of obtaining a drop, yet could not divest themselves of expectation, however unavailing, calling on me by the tender considerations of affection and friendship. The confusion now became general and horrid. Several quitted the other window (the only chance they had for life) to force their way to the water, and the throng and press upon the window was beyond bearing; many, forcing their way from the further part of the room, pressed down those in their passage who had less strength, and trampled them to death.
"From about nine to eleven I sustained this cruel scene, still supplying them with water, though my legs were almost broke with the weight against them. By this time I myself was near pressed to death, and my two companions, with Mr Parker, who had forced himself to the window, were really so. At last I became so pressed and wedged up, I was deprived of all motion. Determined now to give everything up, I called to them, and begged them, as a last instance of their regard, that they would relieve the pressure upon me, and permit me to retire out of the window to die in quiet. They gave way, and with much difficulty I forced a passage into the centre of the prison, where the throng was less by the many dead, amounting to one third, and the numbers who flocked to the windows; for by this time they had water also at the other window. I laid my
self down on some of the dead, and, recommending myself to Heaven, had the comfort of thinking my sufferings could have no long duration. My thirst now grew insupportable, and the difficulty of breathing much increased; and I had not remained in this situation ten minutes before I was seized with a pain in my breast, and palpitation of heart, both to the most exquisite degree. These obliged me to get up again, but still the pain, palpitation, and difficulty of breathing increased. I retained my senses notwithstanding, and had the grief to see death not so near me as I had hoped, but could no longer bear the pains I suffered without attempting a relief, which I knew fresh air would and could only give me. I instantly determined to push for
the window opposite to me, and by an effort of double the strength I ever before possessed, gained the third rank at it-with one hand seized a bar, and by that means gained a second, though I think there were at least six or seven ranks between me and the window. a few moments the pain, palpitation, and difficulty of breathing ceased, but the thirst continued intolerable. I called aloud' Water for God's sake.' I had been concluded dead; but as soon as the men found me amongst them, they still had the respect and tenderness for me to cry out, ‘Give him water l' nor would one of them at the window attempt to touch it till I had drunk. But from the water I had no relief; my thirst was rather increased by it; so I determined to drink no more, but patiently wait the event. I kept my mouth moist from time to time by sucking the perspiration out of my shirtsleeves, and catching the drops as they fell like heavy rain from my head and face; you can hardly imagine how unhappy I was if any of them escaped my mouth.
I was observed by one of my companions on the right in the expedient of allaying my thirst by sucking my shirt-sleeve. He took the hint, and robbed me from time to time of a considerable part of my store; though, after I detected him, I had the address to begin on that sleeve first when I thought my reservoirs were sufficiently replenished, and our mouths and noses often met in contact. This man was one of the few who escaped death, and he has since paid me the compliment of assuring me he believed he owed his life to the many comfortable draughts he had from my sleeves. No Bristol water could be more soft or pleasant than what arose from perspiration.
"By half-past eleven the much greater number of those living were in an outrageous delirium, and others quite ungovernable; few retaining any calmness but the ranks near the windows. now all found that water, instead of relieving their uneasiness, rather heightened it, and Air! air! was the general cry. Every insult that could be devised against the guard was repeated to provoke them to fire on us, every man that could, rushing tumultuously towards the windows with eager hopes of meeting the But these failing, they whose strength and spirits were quite exhaust ed laid themselves down, and quietly expired upon their fellows; others who had yet some strength and vigour left, made a last effort for the windows, and several succeeded by leaping and scrambling over the backs and heads of those in
the first ranks; and got hold of the bars, from which there was no removing them. Many to the right and left sunk with the violent pressure, and were soon suffocated; for now a steam arose from the living and the dead, which affected us in all its circumstances, as if we were forcibly held by our heads over a bowl of strong volatile spirit of hartshorn until suffocated; nor could the effluvia of the one be distinguished from the other. I need not ask your commiseration when I tell you that in this plight, from half an hour after eleven till two in the morning, I sustained the weight of a heavy man with his knees on my back, and the pressure of his whole body on my head; a Dutch sergeant who had taken his seat on my left shoulder, and a black soldier bearing on my right: all which nothing would have enabled me to support but the props and pressure equally sustaining me all round. The two latter I frequently dislodged by shifting my hold on the bars, and driving my knuckles into their ribs; but my friend above stuck fast, and, as he held by two bars, was immovable. The repeated trials I made to dislodge this insufferable encumbrance upon me, at last quite exhausted me, and towards two o'clock, finding I must quit the window or sink where I was, I resolved on the former, having borne truly, for the sake of others, infinitely more for life than the best of it is worth.
"I was at this time sensible of no pain and little uneasiness. I found a stupor coming on apace, and laid myself down by that gallant old man, the reverend Jervas Bellamy, who lay dead with his son, the lieutenant, hand in hand, near the southernmost wall of the prison. Of what passed in the interval, to the time of my resurrection from this hole of horrors, I can give you no account."
At six in the morning the door was opened, when only three-andtwenty out of the hundred and fortysix still breathed. These were subsequently revived. Although the príncipal cause of this mortality must be ascribed to the vitiated atmosphere rather than to Thirst, we nevertheless see some of the frightful phenomena of Thirst exemplified in this narrative. Death by asphyxia (from vitiated air) is generally peaceful, and not at all such as is described in the foregoing. Attention is moreover called to certain passages
in italics. These show that the sensation of Thirst is not merely a Systemic sensation dependent on a deficiency of liquid in the system, but a specific sensation dependent on a local disturbance the more water these men drank, the more dreadful seemed their thirst; and the mere sight of water rendered the sensation, which before was endurable, quite intolerable. The increase of the sensation following a supply of water, would be wholly inexplicable to those who maintain that the proximate cause of Thirst is deficiency of liquid; but is not wholly inexplicable, if we regard the deficiency as the primary, not the proximate cause; for this primary cause having set up a feverish condition in the mouth and throat, that condition will continue after the original cause has ceased to exist. The stimulus of cold water is only a momentary relief in this case, and exaggerates the sensation by stimulating a greater flow of blood to the parts. If, instead of cold water, a little lukewarm tea, or milk-and-water had been drunk, permanent relief would have been attained; or if instead of cold water a lump of ice had been taken into the mouth, and allowed to melt there, the effect would have been very different-a transitory application of cold increasing the flow of blood, a continuous application driving it away. If, therefore, the reader is ever suffering from intense thirst, let him remember that warm drinks are better than cold drinks, ice is better than water.
We must not, however, forget that although, where a deficiency of liquid has occasioned a feverish condition of the mouth and throat, no supply of cold liquid will at once remove that condition, the relief of the Systemic sensation not immediately producing relief of the special sensation, nevertheless, so long as the system is in need of liquid, the feeling of thirst must continue. Claude Bernard observed that a dog which had an opening in its stomach drank unceasingly, because the water ran out as fast as it was swallowed; in vain the
water moistened mouth and throat on its way to the stomach, thirst was not appeased because the water was not absorbed. The dog drank till fatigue forced it to pause, and a few minutes afterwards recommenced the same hopeless toil; but no sooner was the opening closed, and the water retained in the stomach, from whence it was absorbed into the system, than thirst quickly vanished.*
After learning the physiological importance of water, and remembering how the water is continually being removed from the body in respiration, perspiration, and the various excretions, we are greatly puzzled by the great variations which animals exhibit in the quantity they drink. The difficulty is not explained by a reference to the food of the animals, some vegetable feeders requiring large quantities of water, while others subsist for months without drinking, the supply they receive in the vegetables they eat being sufficient for their wants. Dr Livingstone found the elands on the Kalahari Desert, although in places where water was perfectly inaccessible, with every indication of being in splendid condition, and their stomachs actually contained considerable quantities of water. "I examined carefully the whole alimentary canal," he says, “in order to see if there were any peculiarity which might account for the fact that these animals can subsist for months together without drinking, but found nothing. Other animals, such as the düiker (Cephalopus mergens), the steinbuck (Tragulus rupestris), the gemsbuck (Oryx capensis), and the porcupine, are all able to subsist for many months at a time by living on bulbs and tubers containing moisture. Some animals, on the other hand, are never seen but in the vicinity of water. The presence of the rhinoceros, buffalo, and gnu, of the giraffe, zebra, and pallah (Antelope melampus), is always a certain indication of water being within seven or eight miles."+ The only solution of the difficulty which presents itself to my mind is, that
* CLAUDE BERNARD: Leçons de Physiol. Expérimentale, ii. 51. + Missionary Travels in South Africa, p. 56.