CHAP. IV. 



OF THE CHANGES INDUCED ON THE 

 AIR BY THE RESPIRATION OF BIRDS, 

 OF QUADRUPEDS, AND OF MAN". 



SECTION I. 



79. JN OT only, as we have seen, is water 

 necessary to prepare the organization of vegetables, 

 and of the inferior animals, for exhibiting living 

 action, but it is required also by those which be- 

 long to the superior orders. " The whole material 

 world," says Mr Hunter, " has been very properly 

 divided into solids and fluids, these being the only es- 

 sentially different states of matter which we are able 

 to observe. From one of these states into the other, 

 matter appears to be continually passing ; but no spe- 

 cies of matter can assume a solid form without ha- 

 ving first been in a fluid state ; neither can any 

 change take place in a solid, till it be first reduced 

 to, or suspended in, a fluid. The living animal 



