424 TEMPERATURE AND LIFE. 



Occasioually in the latter case, a poison becomes perfectly inactive and 

 iuofleusive, although it Avould prove deadly if the temperature rose a 

 few degrees. This fact is now well understood, and account of it is 

 taken in dealing with toxicology. This explains the frequent contra- 

 dictions between the conclusions of different investigators, because 

 they have not experimented under the same thermic conditions^ and 

 most of them have failed to note the exact temperature. Another 

 proof of temperature on the general functions of the organism is the 

 proof furnished by a comparative study of the resistance of beings to 

 asphyxia. When the temperature is low, asphyxia is slower and more 

 difiicult. A frog immersed in water, its head covered, and only cuta- 

 neous respiration possible, will survive from 6 to 8 hours with the water 

 at 0°. At 15° or 10° it will only live a fourth of this time. To consider 

 another phase of the same question : poisonous plants are more deadly 

 under thermic conditions favorable to their growth than when strug- 

 gling to live in an atmosphere colder or warmer than that adapted to 

 their peculiarities. 



We have been considering so far the influence of thermic variations 

 which are not of necessity deadly. We will now turn our attention 

 to those which are fatal in their effects, first observing that the ef- 

 fects vary according to the species, and also according to certain con- 

 ditions, some intrinsic or inherent in the organisms, others extrinsic or 

 relative to the conditions under which the thermic extremes occur. It 

 is well known, for example, how unequal is the resistance of vegeta- 

 bles and seeds to extremes of heat and cold. Some freeze easily, others 

 with difiBculty. It depends much upon their bulk and the proportion 

 of water contained in their tissues. Some do not die immediately after 

 freezing, even when the thawing is rapid, others only survive when the 

 thawing is slow and gradual. A very important factor is the condition 

 of the vitality. We know that spores of bacteria and seeds of plants 

 withstand degrees of temperature at which neither bacteria nor plants 

 could live. This fact is so well knovrn that it is only necessary to 

 touch upon it. 



It may seem strange that torpid organisms have more resistance than 

 the higher species to adverse circumstances ; yet it is true that the less 

 active the life the less vulnerable it is, and less can exterior forces dis- 

 turb the functions which are already almost dormant and torpid. Cold 

 kills a great number of the lower organisms by reason of the disorgan- 

 ization of the tissues which takes place when congealed, and this dis- 

 organization is complete in proportion to the amount of water which 

 the tissues contiiin. There are, however, many organisms among the 

 cold-blooded class which die before they reach the point of freezing. 

 Invertebrates and plants belonging to warm climates, as well as many 

 microbes, succumb when the thermometer has only reached 0°. In 

 which case the method of death is different, it being produced by a 

 slackening of all the functions. Extreme heat kills plants and animals 



