objects or to carry out manipulations which would be impossible for the white man. 

 There is also clear evidence by Mackworth that local adaptation to cold in the fin- 

 gers can be developed by continued exposure. Mackworth measured the duration and 

 degree of finger numbness by changes in tactile discrimination during and after ex- 

 posure of the bare finger at various temperatures and wind speeds. He carried out 

 his first experiment at Fort Churchill and found a significant difference between in- 

 door and outdoor workers; the latter have less and shorter impairment of finger 

 numbness with similar exposures than the former. As the results might have been 

 interpreted as indicating an ability to discriminate with fewer sensory clues by prac- 

 tice, i.e. a cortical rather than a local change, Mackworth also carried out experi- 

 ments at Cambridge. A number of subjects spent two hours a day in a room, the tem- 

 perature of which was kept at — 10°C. They wore ordinary seamen's clothing, with 

 bare hands. After two hours, one finger was exposed to a blast of cold air and tac- 

 tile discrimination was measured. The rest of the day was spent in normal activi- 

 ties outside the chamber. 



During the first two to three weeks the finger numbness steadily diminished and 

 thereafter kept at a steady level. This result was not due to a learning factor as 

 shown in another experiment in which the subjects only spent one hour a day in the 

 cold room. No decrease in the numbness index was obtained under these conditions. 

 This experiment is an important one as it is the best objective evidence of signifi- 

 cant acclimatization to cold. Studies on the vasomotor changes are not yet complete. 



The fishermen of Nova Scotia who habitually have their hands in cold water also 

 exhibit a degree of adaptation. Uhen the hands are plunged into the water, the nor- 

 mal individual suffers considerable pain, with a sharp rise of blood pressure. This 

 is the basis of the cold pressor test used in clinical medicine as a test of actual or 

 potential hypertensive subjects. The fishermen experience no pain and no rise of 

 blood pressure on immersing their hands in ice water. 



Other factors which were investigated by the Queen's University group included 

 the nutrition of the Eskimo. It is commonly supposed that this dietary consists of a 

 high fat, high protein and low carbohydrate content. The difficulties of determining 

 the average diet is very considerable owing to the very wide daily and individual 

 variation both in composition and calorie value. Within a single week t^ie daily in- 

 take of one individual varied from 2,000-6,000 calories. On one occasion 80% of the 

 calories might be derived from fat, on others it might be as low as 10%. The raw 

 material of the food was available ad libitum, but it appears likely that the very er- 

 ratic feeding habits are related to the more normal situation in which food supplies 

 are dependent on successful hunting and hence are extremely irregular. 



As a result of many dietary experiments in relationship to cold, it has been 

 shown that calorie requirements are considerably increased in the cold. In temperate 

 zones the diet of the soldier provides approximately 3,300 calories. At Fort Chur- 

 chill the rations issued yielded 5,000 calories. Part of this increased metabolic de- 

 mand is due to the hampering effect of arctic clothing, and it is not completely cer- 

 tain if there is a true metabolic increase apart from this. 



210 



