HYBERNATION AND USE OF COLD. 339 



to 5 C. Mammals, which are born blind, and birds which come out of the egg 

 devoid of feathers, cool more rapidly than others. Morphia, and more so, alcohol, 

 accelerate the cooling of mammals, at the same time the exchange of gases falls 

 considerably; hence, drunk men are more liable to die when exposed to cold. 



Artificial Cold-Blooded Condition. CI. Bernard made the important observa- 

 tion, that the muscles of animals that had been cooled remained irritable for 

 a long time, to direct stimuli as well as to stimuli applied to their nerves ; 

 and the same is the case when the animals are asphyxiated for want of O. An 

 ft artificial cold-blooded condition," i.e., a condition in which warm-blooded animals 

 have a lower temperature, and retain muscular and nervous excitability, may also 

 be caused in warm-blooded animals, by dividing the cervical spinal cord and keeping 

 up artificial respiration ; further, by moistening the peritoneum with a cool solution 

 of common salt. 



Hybernation presents a series of similar phenomena. Valentin found that hybernating 

 animals become half-awake when their bodily temperature is 28 C. ; at 18 C. they are in a 

 somnolent condition, at 6 they are in a gentle sleep, and at 1'6 C. in a deep sleep. The 

 heart-beats and the blood-pressure fall, the former to 8 to 10 per minute. The respiratory, 

 urinary, and intestinal movements cease completely, and the cardio-pneumatic movement alone 

 sustains the slight exchange of gases in the luugs ( 59). They cannot endure cooling to C. ; 

 and awake before the temperature falls so low. Hybernating animals may be cooled to a greater 

 degree than other mammals ; they give off heat rapidly, and they become warm again rapidly, 

 and even spontaneously. New-born mammals resemble hybernating animals more closely in 

 this respect than do adults. 



Cold-blooded animals may be cooled to 0. Even when the blood has been frozen and ice 

 formed in the lymph of the peritoneal cavity, frogs may recover. In this condition they appear 

 to be dead, but when placed in a warm medium they soon recover. A frog's muscle so cooled 

 will contract again. The germs and ova of lower animals, e.g., insects' eggs, survive continued 

 frost ; and if the cold be moderate, it merely retards development. Bacteria, e.g., Bacillus 

 anthracis, survive a temperature of- 130 C. ; yeast, even- 100 C. 



Varnishing the skin causes a series of similar phenomena. The varnished skin gives off a large 

 amount of heat by radiation, and sometimes the cutaneous vessels are greatly dilated. Hence 

 the animals cool rapidly and die, although the consumption of O is not diminished. If cooling 

 be prevented by warming them and keeping them in warm wool, the animals live for a longer 

 time. The blood post-mortem does not contain any poisonous substances, nor even are any 

 materials retained in the blood which can cause death, for if the blood be injected into other 

 animals, these remain healthy. 



226. EMPLOYMENT OF COLD. Cold may be applied to the whole or part of the surface 

 of the body in the following conditions : 



(a) By placing the body for a time in a cold bath to abstract as much heat as possible, when 

 the bodily temperature in fever rises so high as to be dangerous to life. This result is best 

 accomplished and lasts longest when the bath is gradually cooled from a moderate temperature. 

 If the body be placed at once in cold water, the cutaneous vessels contract, the skin becomes 

 bloodless, and thus obstacles are placed in the way of the excretion of heat. A bath gradually 

 cooled in this way is borne longer. The addition of stimulating substances, e.g., salts, which 

 cause dilatation of the cutaneous vessels, facilitates the excretion of heat ; even salt water 

 conducts heat better. If alcohol be given internally at the same time, it lowers the 

 temperature. 



(&) Cold may be applied locally by means of ice in a bag, which causes contraction of the 

 cutaneous vessels and contraction of the tissues (as in inflammation), while at the same time 

 heat is abstracted locally. 



(c) Heat may be abstracted locally by the rapid evaporation of volatile substances (ether, 

 carbon disulphide), which causes numbness of the sensory nerves. The introduction of media 

 of low temperature into the body, respiring cool air, taking cold drinks, and the injection of 

 cold fluids into the intestine act locally, and also produce a more general action. In applying 

 cold it is important to notice that the initial contraction of the vessels and the contraction of 

 the tissues are followed by a greater dilatation and turgescence, i.e., by a healthy reaction. 



227. HEAT OF INFLAMED PARTS. "Calor," or heat, is reckoned one of the fundamental 

 phenomena of inflammation, in addition to rubor (redness), tumor (swelling), and dolor (pain). 

 But the apparent increase in the heat of the inflamed parts is not above the temperature of the 

 blood. Simon, in 1860, asserted that the arterial blood flowing to an inflamed part was cooler 

 than the part itself, but this has been contradicted. The outer parts of the skin in an inflamed 

 part are warmer than usual, owing to the dilatation of the vessels (rubor) and the consequent 



