Zoology: How the Camel Conquers Thirst

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Myths about the camel and its thirst-resistance are older than the Sphinx—and almost as durable. Well into the modern age of science, men accepted the notion that the evil-tempered animal could store a two-week supply of water in its humpor in a great, cistern-like stomach. The hump theory was the first to be discarded as so much humph. What the camel carries on its back is a reserve of fatty tissue to be consumed when the rest of the camel runs out of fuel. The story about the parched Bedouin who slaughtered his favorite camel to drink the water in its stomach was far more tenacious. Not until the 1950s did zoologists puncture it as a romantic mirage.

Albumin in the Plasma. But for all the debunking dissections, the camel's thirst-quenching secret remained hidden. Then, a young Israeli veterinarian went to work on the ship of the desert. The answer, says Dr. Kalman Perk, 34, of Rehovot's Hebrew University, is in the camel's bloodstream. The plasma has an extraordinary high content of a kind of albumin, which enables the blood to retain its water and maintain its volume and fluidity even when the water in the camel's tissues has been markedly depleted.

When most animals are exposed to heat, they keep cool by sweating or panting. Not the camel. Its nappy coat insulates it against external temperatures, and it can withstand body temperatures of up to 104.9°F. before its sweat glands begin to function. As the camel is cooled by its evaporating sweat, it can lose up to 30% of its total body weight without harm because the water content in the blood plasma stays close to normal, permitting the blood to circulate freely. Camels loping in after a two-week journey across the sands are often in an extremely desiccated condition; once the thirsty animals reach water they may drink as much as 30 gallons in ten minutes. As they take in the water, the red cells in their bloodstream swell to as much as 240% of their normal size. In other animals, the cells hemolyze, or burst, causing death if their total volume is increased to more than 130%. In man the danger level is 165%.

Injected Rabbits. Dr. Perk has found that other animals that are native to hot, dry environments, such as Syrian Damascene cattle, share the camel's secret of survival and have higher albumin levels than other breeds. He has carried out successful experiments on rabbits in an effort to give them the camel's water-retaining capacity. Rabbits injected with camel albumin were kept for seven days without water in 104°F. heat, and lost only 3% or less of their body water; control rabbits not given the injections lost from 5% to 10% and were close to death.

In hope of finding a way to make man more immune to desert heat, Dr. Perk plans to begin experimenting on human volunteers next summer. Meanwhile, there is evidence that some humans may already have some of the camel's thirst-conquering equipment. A Tel Aviv researcher has collected data showing that Yemenite Jews, traditional desert dwellers, have a significantly higher blood-albumin level than Jews of European lineage.