VITAL PRINCIPLE. 31 



ture approaching the boiling point. The tendency of the 

 fluids to fly off in vapour, becomes too great for the vital 

 power to restrain. 



As the medium in which organized bodies live, is sub- 

 ject to great variations of temperature, it is obvious, that 

 unless Nature had provided some means of defence, many 

 races would soon be extinguished, and Others confined in 

 their operations. But, in all the situations in which orga- 

 nized bodies are placed, the means of protection against the 

 vicissitudes of temperature are liberally provided. The 

 locomotive faculty assists their escape from the scene of 

 danger ; and, where this is wanting, a covering of a body 

 which conducts heat imperfectly, is bestowed to prevent 

 the diminution of temperature, and various means are 

 every where employed to check its pernicious increase. It 

 is probable, that all organized beings, vegetable as well as 

 animal, have an inherent power of generating cold or heat, 

 according as circumstances require. Some curious experi- 

 ments were performed in illustration of this subject by 

 HUNTER *. 



But the resources of organized bodies, employed to se- 

 cure a suitable temperature, may be discovered in the 

 circumstances of their physical distribution. Some are 

 found subsisting under the influence of a vertical sun, 

 while others survive the piercing colds of the arctic re- 

 gions;- some prefer the sea-shore, others the summit of the 

 mountains ; some live in the water, others on the dry land. 

 To these different circumstances, there is an admirable 

 adaptation of structure and disposition with respect to tem- 

 perature ; so that no part of the earth of the waters can be 

 considered as destitute of life. In these different stations, 

 the different species can perform all the functions of exist- 



* Phil. Trans. IT? $,-1778. 



