412 TEMPERATURE AND LIFE. 



order to facilitate the passage of air through the mouth. He breathes 

 quickly, sonietiuies with great rapidity, iu order to induce a more 

 abuudaut exhalatiou of moisture. It is much to be desired that a study 

 ot refrigerating mechauisms be pursued in behalf of those beings 

 which have no perspiring capabilities, as such a study would be fruitful 

 in interesting results. 



When the internal temperature of man is at a low point, suflBcieut 

 refrigeration is effected simply by the flow of blood, which is always 

 towards the surface. Influenced by external heat the cutaneous tubes 

 expand, by this means they are able to contain a larger quantity of 

 blood, and radiation from the skin is thus increased, resulting in a 

 cooling tendency, which spreads through the entire system by reason 

 of the circulation of the blood, which is also accelerated, and thus 

 facilitates refrigeration. 



From a physiological point of view the organism is less fully equipped 

 for protection against extreme cold. Cold however is less dangerous 

 to organic life than heat, and for this reason nature has prepared it 

 more perfectly to meet the latter. A sensation of cold stimulates 

 animal life to activity, and by this very result i)roduces warmth. More- 

 over animals of cold climates have in the winter a heavier growth of 

 fur, which serves as a protection. In addition to this resource, we shall 

 l)ointout the fact that cold contracts the tubes of the skin which dimin- 

 ishes refrigeration; respiration is accelerated and with it organic com- 

 bustion. The need of food is greater and it is eaten in larger quanti- 

 ties, all of which introduces into the system a greater quantity of 

 combustible material. Observe for a moment the immense importance 

 of the nervous system in its effect upon bodily temperature. This fact 

 has been clearly demonstrated by many experiments in physiology, as 

 well as by clinical observations. 



To epitomize, the heat of animals is generated by chemical phenomena 

 which takes place within the organism. With some species these phe- 

 nomena are very active and the temperature proportionately high. In 

 addition they are furnished with a regulating apparatus so arranged 

 tliat within certain broad limits oscillations in the external temperature 

 modify only to a slight degree, or insensibly, their internal tempera- 

 ture. These are the homeothermic species. With the others (the 

 heterotherms) in which chemical phenomena are feeble and inactive, 

 tliere is a temperature correspondingly low. These, moreover, have no 

 ])rotection against the influence of the outside temperature, following 

 closely its variations. Their own temperature is, in fact, the result of 

 tlieir environment, more than of the chemical phenomena within. This 

 difference between warm and cold blooded animals is considerable, for 

 in the case of the former, under average normal conditions, the exter- 

 nal temperature has no, or little, action upon the temperature of the 

 animal. 



Calorification is a general i)heiion)ena iimong animals from protozoan 



