44 Causes of Disease. 



pletely recover from such a condition. Frogs are said to remain 

 viable for hours subjected to a temperature of -2.5° C, with the 

 heart frozen soHd (anabiosis). 



According to Koch, resuscitation is possible only by gradual thawing 

 and providing only a part of the water present in the body has been 

 actually frozen ; in case of rapid thawing, violent diffusion currents appear 

 between the water emerging from its crystalline form and the concentrated 

 albuminous solutions of the blood and tissues, which may destroy the 

 tissues (Koch, Ziegler). 



Hibernating animals sleep but lightly with a blood temperature 

 of 6° C, but soundly at 1.6° C. ; their cardiac beats sink to eight 

 to ten each minute ; breathing is almost suspended, the movement 

 of the lungs caused by the heart action alone carrying on the 

 feeble gas diffusion in the lungs (Samuel). 



The hair and feathers (especially the winter pelt) of animals 

 lessen the loss of heat by radiation and by convection of the 

 [warm] air from the surface of the body ; in consequence 

 of which animals are seen to endure with ease the ordinary cold, 

 providing they are well nourished, move about freely and thus 

 produce heat abundantly. [The loss of this protective element 

 or the presence in the hair of much moisture favoring the ready 

 convection of the heat from the body surface reduces tremen- 

 dously the power of resistance to cold ; and one finds the cattle 

 in the prairies freezing to death in a rain at a temperature con- 

 siderably above ice-forming temperature, although were the hair 

 dry and capable of holding the layer of warmed air close to the 

 skin the animals would have shown no signs of discomfort.] 

 If there be diminution of heat-production because of insufficient 

 nutrition, and extreme cold, even well-pelted animals (hares and 

 deer) and birds may be frozen to death. Death by freezing takes 

 place by loss of sensibility of the nervous system, with fall of 

 body temperature, diminution in the frequence of the cardiac 

 and respiratory movement, cerebral anaemia, loss of muscular 

 power and blood coagulation. 



The local action of cold, varying with duration of exposure 

 and intensity, causes tissue changes of the same types as in 

 burns (frosting, congelation). Primarily there results a constric- 

 tion of the vessels of the part exposed (local anaemia), after 

 which, if the cold continue, the nerves and muscle tissue of the 

 vessel walls become paralyzed and dilatation of the vessels ensues 

 with increased blood content, this condition usually returning to 



