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During the initial stages of rewarming from hypothermia, there is a continued cooling of the core, or after-drop in temperature, that has been attributed to the return of cold blood due to peripheral vasodilatation, thus causing a further decrease of deep body temperature. To examine this possibility more carefully, subjects were immersed in cold water (17 degrees C), and then rewarmed from a mildly hypothermic state in a warm bath (40 degrees C). Measurements of hand blood flow were made by calorimetry and of forearm, calf, and foot blood flows by straingauge venous occlusion plethysmography at rest (Ta = 22 degrees C) and during rewarming. There was a small increase in skin blood flow during the falling phase of core temperature upon rewarming in the warm bath, but none in foot blood flow upon rewarming at room air, suggesting that skin blood flow seems to contribute to the after-drop, but only minimally. Limb blood flow changes during this phase suggest that a small muscle blood flow could also have contributed to the after-drop. It was concluded that the after-drop of core temperature during rewarming from mild hypothermia does not result from a large vasodilatation in the superficial parts of the periphery, as postulated. The possible contribution of mechanisms of heat conduction, heat convection, and cessation of shivering thermogenesis were discussed.

The rate of umbilical blood flow has been measured in sheep foetuses between the 60th and the 143rd day of pregnancy. METHODThe foetuses were delivered under saline at 370 C. by the technique of Huggett (1927) (Greenfield, 1948). In most cases observations commenced within a few minutes of opening the uterus. RESULTSThe accuracy ofthe measurements naturally increased as experience was gained in handling the animals and apparatus, and as improvements were effected in the design and construction of the plethysmograph and recording gear. In order to assess the value of the data in this paper, Table 1

Studies have been made by a number of workers on the level of the outflow from the spinal cord, of vasomotor nerves to the hind limbs in the dog (Bayliss & Bradford, 1894), and in the monkey (Geogehan, Wolf, Adair, Hare & Hinsey, 1941 It was considered that a study of the foot blood flow responses to raising body temperature in a series of patients with complete lesions of the spinal cord at various levels would provide evidence of the level of vasomotor outflow to the foot in the conscious subject. The vasomotor impulses concerned would be those derived from neurones whose activity is modified by thermal change. The level of outflow thus determined would not necessarily be identical with that demonstrated by direct stimulation of the pre-or post-ganglionic trunks, or with that deduced from histological surveys of the sympathetic efferent pathways.At the same time it was possible to determine whether the impulses arising from the isolated cord could be modified by changes in temperature which were larger than the increments in temperature known to affect the central temperature regulating mechanism. METHODSSubject&. The subjects were twenty-one paraplegic patients of both sexes at the National Spinal Injuries Centre, who were free from active infections of the urinary tract or other disorders, such as bedsores. Nineteen had complete lesions of the spinal cord at levels ranging from C5 to L2, and two cauda equina lesions below L3-5 and L4 respectively. The lesions were the result of

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