4IO ARTIFICIAL REDUCTION OF BODILY TEMPERATURE IN ANIMALS. 



in this way able to resuscitate full-grown animals whose temperature 

 had been reduced to 9 C. and Howarth young animals even when the 

 temperature had been reduced to 5 C. Mammals born blind and 

 birds born without feathers, if left to themselves, suffer reduction in 

 temperature more rapidly than others. Morphin, and in still greater 

 degree alcohol, accelerate the reduction in the temperature of mam- 

 mals, the gaseous interchange at the same time falling considerably, 

 and for this reason drunken persons are more readily exposed to the 

 danger of death from freezing. 



Knoll lowered the temperature of rabbits by means of intravenous infusion 

 of an ice-cold indifferent solution of sodium chlorid. He found reduction in 

 pulse-frequency, prolonged systole, paralysis of the cardiac branches of the vagus, 

 primary increase -and secondary reduction in blood-pressure, accelerated, super- 

 ficial breathing and later diminished frequency of breathing. 



Cl. Bernard made the remarkable discovery that the muscles of 

 animals whose temperature had been reduced maintain their irritability 

 for a longer time, with respect to direct stimuli, as well as to 

 stimulation through the nerve. He found the same condition when the 

 animals were asphyxiated through deficiency of oxygen. Artificial 

 cold-bloodedness, that is, a condition in which the temperature of warm- 

 blooded animals is reduced, with preservation of the irritability of 

 muscles and nerves, can be developed in warm-blooded animals also by 

 division of the cervical cord while artificial respiration is maintained, 

 and further by application of a cool solution of sodium chlorid to the 

 peritoneum. 



Hibernation, which is due essentially to the lowering of the temperature of the 

 animals, exhibits a series of analogous phenomena. Valentin found that the 

 marmot begins to be only half awake when the bodily temperature reaches 28 C. ; 

 at a temperature of 18 C. it is soporose; at 6 it exhibits shallow and at 

 1 6 C. deep sleep. At the same time the heart-beats fall to 8 or 10 in a minute, 

 with reduction in the blood-pressure. The respirations and the movements of the 

 bladder and the intestine cease entirely, and only the cardio-pneumatic movement 

 maintains the slight diffusion of gases in the lungs. The temperature does not 

 fall as low as o, but the animals awaken before the temperature has fallen to 

 this level. At a temperature of o C. no further dissociation of the oxy hemo- 

 globin would take place. Hibernating animals, indifferently whether in the 

 waking or in the sleeping state, may, however, survive an artificial reduction of 

 temperature down to 1 C. and recover spontaneously. Hibernating animals, 

 therefore, submit to a greater reduction of temperature than other mammals. 

 Under such circumstances, they yield up their heat rapidly and they are able to 

 renew their heat with rapidity even spontaneously. Newborn mammals more 

 closely resemble hibernating animals in this respect than do adult animals. The 

 animals can be awakened from their winter's sleep by sensory stimulation and in- 

 creasing temperature through the agency of the nerve-centers. 



In cold-blooded animals exposed to great cold the temperature can be reduced 

 almost to the freezing-point tenches can be frozen into ice. In the state of cold 

 their metabolism is greatly lowered and the animals are apparently dead, although 

 they recover rapidly when exposed to warmer surroundings. Under favorable con- 

 ditions animals frozen into a mass of ice may be resuscitated the frog. If, for 

 example, however, the fluids throughout the body have been frozen into ice, the 

 animals will die, for the reason that with the formation of ice in the tissues, the 

 gases are expelled in the form of bubbles and the salts separate in the form of 

 crystals. The germs and ova of lower forms of animal life, as, for instance, the 

 eggs of insects, survive long-continued, severe cold. A moderate degree of cold 

 only retards their development. Snakes tolerate an external temperature of 

 25, frogs a temperature of 28, myriapods and infusoria a temperature of 

 50, snails for days a temperature of 120. Germs, grains of seed and spores 

 of fungi exposed to a temperature of 200 are capable of germinating after 



