AND ANIMAL LIFE. 65 



LIV. The alterations which the blood under- 

 goes in the lungs are probably various ; that of 

 colour is apparent : but this may be only one* and 

 the least of a series, connected with the produc- 

 tion of animal heat ; or, for any thing that we 

 know, may be an effect altogether independent 

 of those principles which maintain the tempera- 

 ture of the constitution. When venous blood, 

 without the body, is exposed to the action of 

 atmospheric air, it assumes the florid colour of 

 the arterial ; but we are not aware that this is 

 accompanied by the generation of heat. 



LV. It is stated by LEGALLOIS, that he could 

 cool an animal to such a degree, during life, by 

 inflation, as to kill it ; and I have not the least 

 doubt that the temperature is, at all times, by 

 such means, materially affected. If we cannot 

 succeed in the application of this process when 

 the animal is alive, and when it in part seconds 

 our intentions, how can we expect to be more 

 fortunate when the animal is mutilated. The 

 combination of gases, and the formation of salts 

 and other substances, are regulated by definite 

 laws ; and it is well known, that if proper pro- 

 portions are wanting, or if those circumstances 

 are absent which are necessary to promote che- 

 mical action, no change whatever takes place. 

 But shall we suppose that the powers of life are 

 governed by no principle, or, in more correct 

 terms, that the action of those agents which sup- 

 E 



