418 TEMPERATURE AND LIFE. 



poiut however, since it is complicated by the iutiodiiction of a new 

 factor — the suffocation of tlie inhabitants of the water as a result of 

 this congelation. The Mediterranean Sea is less cold, the temperature 

 at the bottom being about 12° or 13° The Red Sea rises to 21°, and 

 at the surface to 32°. The variations are less in the center, not exceed- 

 ing 34° C. It is therefore on the earth and in the air that the extremes 

 of temperature are found. The immense influence of the rays of the 

 sun upon temperature should be taken into account. A thermometer 

 which registers 27° in the shade will rise to 31° when placed in the 

 sun, and when resting upon a bit of black cloth it will reach 80°. A 

 thermometer i)laced on the helmet of a cuirassier and exposed to the 

 sun will rise to GOo or 70°, and in a compartment of a furnace it rises to 

 75° O. On the other hand we must not forget that life exists in regions 

 where the temperature reaches 90° and 98° (J (Hooker, Floureus, etc.). 

 This conclusion, therefore, is reached, that there are some creatures 

 which can live at +IOO0 and others at — 00° or — 70°. These figures 

 represent the extremes of temperature to which living beings are ex- 

 posed under actual terrestrial conditions, but they do not represent 

 those which certain of these classes can resist, for certain spores of 

 bacteria resist more than -flOOo and — 100° O, according to recent ex- 

 periments. Let us admit at the start, to simplify matters, that life can 

 be sustained at — 150° and at -f 150°. Are all these creatures able to 

 sustain life with impunitj^, even for a short time, in such extremes of 

 temperature "? Possibly so, but only for a limited space of time, and 

 surrounded by a nonconductor. This proves nothing; the only inter- 

 esting phases of this question are the facts or experiments which relate 

 to the results obtained by organisms remaining in such extremes for a 

 prolonged length of time — interesting where they succumb, being suf- 

 focated or frozen, as well as when they are able to survive by pre- 

 serving their normal temperature. We will not dwell upon those cases, 

 which are both numerous and interesting, where man and animal have 

 endured for a few moments or seconds extremes of temperature, only 

 considering the cases where their continuation is sufficiently prolonged 

 for the temperature to affect them. 



There is for every species of animal and vegetable, indeed even for 

 each variety, a thermic opti)num, that is to say, an average of tempera- 

 ture which is most favorable to its growth and development. It should 

 not be forgotten, however, that with all species of organic life a certain 

 adaptation is possible, the limits of which are more or less restricted. 

 In many instances it is possible to sustain life among animals in a 

 medium which would have been fatal to them if they had been suddenly 

 introduced into it, by carefully managing the conditions and transi- 

 tions. This fact is especially recognized in chemical elements, of which 

 many instances have been given. It is true as well of thermic condi- 

 tions. At the same time, even when adaptations are made, new envi- 

 ronment acts on the organism, intiuencingand modifying its structure 



