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Show 329 quantitatively appeared a matter of great interest. From a series of observations made daring very hot days, ( 108° to 114° F.,) measuring the amount of water drank and the volume of urine secreted, the conclusion was arrived at that two liters of water leave the body in the gaseous state during the twelve day hours. If, however, engaged in heavy work, such as packing mules, olimbing mountains, & c, the amount is nearly doubled. The volume of urine was found to average only one- twelfth to one- fourteenth of water drank. The latter had generally 70° F.; but that the lower temperature of the drinking water has but very little to do with the cooling of the body may be shown by the following calculation: Let it be supposed that a man of 70 kilograms weight drinks 2 liters of water of 70° F., and that the specific heat of flesh is the same as that of water, which is very nearly correct, as the body consists of about 75 per cent, of water, we have the following equation: 70 X 98.5 - f 2 X 70 ^ m 72 - OT- 7 The blood temperature would therefore be decreased to 97° .7 F., or not more than 0.8°. That this is not sufficient cooling effect for twelve hours in such a hot climate is evident. But how different the result if we calculate the amount of heat becoming latent byconversion of two liters of water into vapor! According to Regnault, the latent heat of one gram water converted into vapor of a certain temperature is expressed by the following formula: W = 606.5 + 0.305 t. tin here the temperature of blood- heat = 36°. 8 C, ( 98°. 5 F.) Hence, the number of calorics = W, becoming latent by evaporation of two liters of water, is equal to 1,235,000; which, should the evaporation suddenly take place, would suffice to depress the temperature of the body ( 70 kilogram s weight) for 17°. 6 C, or 31°. 7 F.! But this cooling effect does not take place at once; the two liters evaporate gradually during twelveTiours; hence, the cooling effect per hour is = 2°. 6 F. This, therefore, would be the amount which the temperature of the body would be raised if no more water were available for evaporation. How soon a person must succumb from thirst in such a hot climate becomes evident. The first symptom is delirium, and when arrived at that state the efforts to save are rarely crowned with success. A number of cases were related to me where helpless sufferers have been picked up, but died after one or two days, in spite of all care bestowed upon them. Even old pioneers, miners in the mountains, who were well acquainted with the dangers of crossing the desert in a new direction, deviating from the old trails leading to water, perished, overcome with thirst and fatigue; not by sunstroke, which is almost unknown there. It appears that this latter calamity only takes place when the hot atmosphere is at the same time charged with humidity, interfering with the free evaporation from the body. It is evident that by drinking large quantities of water, the blood must acquire a high degree of dilution; hence all the juices, those of digestion included, the gastric and pancreatic, must be more diluted than usual, and the power of digestion weakened. Therefore, but a limited amount of food is assimilated, no matter how much is eaten, and a great deal leaves the body undigested, with the feces, which generally are of a thin consistency. As another consequence we observe the decrease of muscular power; every exertion requires an increase of combustion, whose result, the heat, has to be converted into mechanical force. But everything tends here to keep the oombustion at a low state. Hence it is preferable to be vegetarian in this climate, as a consumption of meat produces an increase in the number of blood- corpuscles, the absorbers and carriers of the oxygen, the oxidizing surface. The Mohave Indians inhabiting the hot Colorado Valley below Fort Mohave are exclusively vegetarians. It is worth mentioning that after consuming fatty matter a considerable portion is exuded unchauged by the skin. It was also observed that while meat increases the thirst immensely, fat suppresses it considerably. Repeatedly I was assured, that in crossing the desert, alcoholic drinks and tobacco have a very injurious effect, as a person usiug them succumbs muoh sooner. A resident of Saint Thomas, a little oasis on the Muddy Creek in Southern Nevada, stated that two or three days previous to undertaking a desert trip he abstained from any stimulating material. It is a question of interest in what proportion stand the quantities of water evaporated by the lungs and by the skin. The average volume of air inhaled during twelve hours is, according to Carpenter's Physiology, 5,000 liters. This volume leaves the lungs perfectly saturated with moisture* at blood temperature; hence the maximum amount of water removable by exba- * At least in the hot desert climate, where the inhaled air is hotter than the body. The repeated introduction of the wet bulb of the psychorometer into the nost rite substantiated this fact. |