412 TEMPERATURE AND LIFE. 



order to facilitate the passage of air tbrougli the moutli. He breathes 

 quickly, sometimes with great rapidity, in order to induce a more 

 abundant exhalation of moisture. It is much to be desired that a study 

 of refrigeratiug mechanisms 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, sufficient 

 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 tiie 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 produces 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 

 point out 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 

 that within certain broad limits oscdlations 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 jihenomena are feeble and inactive, 

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

 protection against the influence of the outside temperature, following 

 closely its variations. Their own ten^perature is, in fact, the result of 

 their envirojiment, more than of the chemical phenomena within. This 

 <lifterence 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 phonomena among animals from protozoan 



