The amount of metabolic energy spent in transporting the body mass of the subject over a unit of distance has been defined as the energy cost of locomotion, or regarding to swimming, cost of swimming. The differences in the cost of swimming between the individuals seem to be influenced by two main factors, the hydrody-namic resistance and technical skill of the swimmer. The lower cost of swimming showed by females has been attributed to a smaller hydrodynamic resistance due to their smaller size, larger percentage fat and more streamlined position. However, the difference in cost of swimming between males and females disappears when correcting for body size. With regard to children, the higher energy cost of swimming when correcting for body size may be caused by the lower swimming technique showed by them. For individuals with the same anthropometric characteristics, the better swimming technique and larger size of propelling surface, associated with higher propelling efficiency, may decrease the energy cost of swimming. When comparing different types of strokes, the most economical stroke is crawl, followed by backstroke , irrespective the swimming velocity. Butterfly is the less economical at low velocities (< 0.8 m·s-1). However, above that velocity the breaststroke become the less economical stroke.

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The rectal temperature of normal healthy camels at rest may vary from about 34°C to more than 40°C. Diurnal variations in the winter are usually in the order of 2°C. In summer the diurnal variations in the camel deprived of drinking water may exceed 6°C, but in animals with free access to water the variations are similar to those found in the winter. The variations in temperature are of great significance in water conservation in two ways. a) The increase in body temperature means that heat is stored in the body instead of being dissipated by evaporation of water. At night the excess heat can be given off without expenditure of water. b) The high body temperature means that heat gain from the hot environment is reduced because the temperature gradient is reduced. The effect of the increased body temperature on heat gain from the environment has been calculated from data on water expenditure. These calculations show that under the given conditions the variations in body temperature effect a considerable economy of water expenditure. The evaporative heat regulation in the camel seems to rest exclusively on evaporation from the skin surface (sweating), and there is no apparent increase in respiratory rate or panting connected with heat regulation. The evaporation from isolated skin areas increases linearly with increased heat load. The critical temperature at which the increase sets in is around 35°C. The fur of the camel is an efficient barrier against heat gain from the environment. Water expenditure is increased in camels that have been shorn.

A review of major ideas pertaining to the importance of the body size of animals. It discusses the size range of living organisms and the possibilities and constraints that result from the design of animals and the materials used in their supporting structures. The change in size of similarly organized animals is considered in the light of the principles of scaling, with examples chosen both from morphology and physiology. The mechanical consequences of body size in relation to locomotion is also discussed.

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