The effects of extremely cold and hot environments on body proportions of rats were studied. These effects included changes in the length of the tail, trunk, extremities, cranio-facial and nasal dimensions, in bone robusticity and bone shape, in the size of the ear and in some characteristics of the skin and hair. Since animals in both extreme temperatures fail to gain normal body weight, all changes were also studied in a group of starving rats. Because of the lower body weight and its concomitant reduction of body measurements, absolute values were avoided for analysis and all parameters were related to neurocranial length and trunk length. Such a triple experimental approach (response to cold, heat, and starvation) combined with a two-fold frame of reference (neurocranial length and trunk length), as well as statistical corrections for body weight loss, made it possible to differentiate between nutrition-specific and temperaturespecific responses under conditions of extreme temperature exposure. Moreover, some attention was given to endocrine pathways involved in some morphological changes. The methodological advantages of a multi-experimental approach over a single-experimen tal technique were demonstrated.A considerable body of information has accumulated in the field of experimental biology on the effects of extreme cold and heat exposure on physiological and biochemical conditions of various body tissues. Experimental work on humans exposed temporarily to extreme temperatures has concentrated on such reactions as shivering and non-shivering thermogenesis, oral, rectal, and skin temperature, pulse, sweat and metabolic rates, insulation as related to skin fold thickness, and peripheral circulation in fingers, hands, and feet.However, the important anthropological problem of body proportions in human populations and their relationship to temperature differences has so far been treated mainly on a comparative and distributional basis with interpretations usually following the nineteenth century ecological "rules" of Bergmann and Allen. In fact, not even constitutional anthropology has ever made an attempt to analyze the problem of body constitution in a lower mammal, its sexud dimorphism, dependence AM. J. PnYs. ANTHROP., 39: 427460.on endocrine activity, nutrition and temperature exposure. The only exception is found in the study by Steegmann and Platner ('68) on experimental cold modification of cranio-facial morphology in the rat, attempting to "clarify the process by which the 'Arctic Mongoloid Face' has come to look as it does."The only problem pertaining to body proportions in a lower mammal that has been studied extensively is the problem of relative tail-length in cold and heat-exposed mice and rats (Sumner, '09; Przibram, '22, '25; Ogle, '34; Ashoub, '58; Harrison, '58, '59, '60, '62, '63; Harrison et al., '59; '64; Knoppers, '42; Barnett, '65; Thorington, '66, '70; Sundstroem, '27; etc.). The authors of these studies found that absolute trunk length is shorter in heat-exposed animals, tha...

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All metatarsals have a significantly greater robusticity i n the male than in the female rat. The robusticity formula of the rat's foot is 1 > 5 > 2 > 3 > 4. In bipedal rats that formula remains unchanged, but the robusticity of the metatarsals is increased especially in females. The tripod arrangement of the human foot with its particular robustness of the marginal metatarsals 1 and 5 and a strong calcaneum has been related to upright posture. The similar robusticity pattern in the rat's marginal metatarsals 1 and 5 raises the question of whether that part of the formula might not represent a more general plantigrade pattern.In a paper dealing with fossil foot bones, Day and Napier ('64) have demonstrated that the robusticity of the metatarsals is a n important indicator of weight distribution through the foot. Defining the robusticity index as the mid-shaft diameter times one hundred over the length, the authors have shown that in modern man and in the Olduvai foot, the fifth metatarsal is the second most robust after the first while in the lowland and mountain gorilla, it is the least robust. However, the third metatarsal of the Olduvai foot has a greater robusticity than the fourth, while in modern m a n that order is reversed. Thus, the robusticity formula for modern man is: 1 > 5 > 4 > 3 > 2 while for Olduvai it is 1 > 5 > 3 > 4 > 2; and for the two gorillas it is: 1 > 2 > 3 > 4 > 5. From this the authors conclude that the particular robustness of the marginal metatarsals and a stout calcaneum, are the skeletal adaptations of the foot to upright stance and fully bipedal gait i n modern man, and that 01-duvai man possessed the basic structural requirements for it as well. Campbell ('66) has compared this arrangement of the human foot bones to the stable character of a tripod.In the present study an attempt was made to (1) establish the formula of metatarsal robusticity for a relatively unspecialized plantigrade animal such as the rat; ( 2 ) determine whether there exists a AM. J. PHYS. ANTHROP.. 36. 22S234.sexual dimorphism of metatarsal robusticity; and ( 3 ) determine whether the robusticity of the metatarsals could be altered experimentally by increasing the weight-bearing load in the foot of bipedal rats. MATERIAL AND METHODSIt is customary to establish the index of robusticity of a long bone by relating its width, as measured at the mid-point of its shaft, to its total length. However, such a n index was considered unsatisfactory in the rat for the following reasons: (1) a mid-point on the shaft can be established with sufficient accuracy on a relatively large bone but is difficult to establish on the small metatarsals of the rat's foot; ( 2 ) such a mid-point is a n arbitrary geometrical point with no special physiological or biomechanical significance; ( 3 ) a diameter at that point expresses only a single spatial dimension instead of the complete spatial quality of the bone as a whole. Total length was therefore related to the cubic root of the weight. Such a ponderal index, customary in som...