CHAP, v.] NUTRITION. 819 



feeble as the rate is quickened, the beats become irregular, and 

 filially cease. Either of these t\vo events alone and certainly both 

 together arc' enough to bring the working of the bodily mechanism 

 bo an end; but other tissues beside the heart and the respiratory 

 .cut iv an- suffering in the same way, notably the rest of the 

 central nervous system. This too is being hurried on unduly in its 

 inner changes, so that not only consciousness is lost and other 

 objective manifestations of nervous action go wrong or fail, but that 

 regulative grasp of the central nervous system on the tissues of the 

 body at large is loosened, and tumult takes the place of order. 

 Whether this or' that sign of disorder comes to the front, whether 

 for instance convulsions take place, would appear to depend upon 

 the exact turn taken by the abnormal events. In heat-stroke, 

 more commonly known as sun-stroke, the essential condition of 

 which seems to be a rapid rise of the temperature of the body 

 owing to a sudden failure of the thermotaxic mechanism, the ' 

 symptoms vary. Sometimes the heart suddenly gives way, at other 

 times the respiratory centre seems to be more directly affected ; 

 sometimes convulsions make their appearance, but more commonly 

 death takes place through a comatose condition of the brain, an 

 initial phase of excitement of the central nervous system being 

 not unfrequently witnessed. 



Mammalian muscle, it will be remembered, 84, becomes rigid 

 at about -50; but death probably always occurs before that higher 

 temperature is reached by the blood, so that a sudden rigor mortis 

 from heat (rigor caloris) cannot be regarded as a factor in death 

 from exposure to too great heat. But should that temperature 

 ever be reached by the living body, all we know leads us to infer 

 that a sudden rigidity of the whole body would at once put an 

 abrupt end to life ; to suppose that a human body can truly 

 register this or a higher temperature while remaining alive, to say 

 nothing of shewing no tokens of distress, entails the supposition 

 that such a body can differ from its fellows in its absolutely 

 fundamental qualities, and yet make no other sign. 



539. Effects of Great Cold. The effects of a too great 

 lowering of the temperature of body, which is generally the result 

 of too great external cold and rarely if ever arises from internal 

 causes lowering the metabolism and thus the production of heat, 

 are in their origin the reverse of those of a too high temperature. 

 The metabolism of the tissues is lowered ; and not only are the 

 katabolic changes which lead to the setting free of energy thus 

 affected, but the anabolic changes also share in the depression. 

 The "living substance" falls to pieces less readily, but is also 

 made up less readily; and could this slackening of metabolism 

 be carried on in the several tissues at a rate- proportionate to 

 the rate at which each tissue lives, life might thus be brought 

 to a peaceful end by gradual arrest of the life of each part 

 of the whole body. And indeed in some eases, where the lowering 



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