$2 LECTURE IX. 



mals: thus we know that a Flea and a Grass- 

 hopper are capable of springing to a much greater 

 distance in proportion to the length of their bodies 

 than any quadrupeds; for a Flea is capable of 

 springing at least 200 times its own length; 

 whereas the Jerboa and the Kanguroo, in their 

 most powerful springs fall very far short of the 

 same proportional distance. 



We have before observed that insects are not 

 provided with lungs, like the higher orders of ani- 

 mals, but that they breathe by means of a certain 

 number of pores or small openings, generally 

 placed on each side the body, and which are con- 

 tinued into very numerous branches, dispersed 

 about the body of the animal. If the lateral 

 pores or breathing-holes in insects be stopped^ 

 by rubbing them with oil or any other sub- 

 stance capable of excluding the air, the animal, 

 after a certain time, falls into convulsions and 

 dies. 



It has been a matter of doubt among natu- 

 ralists, and particularly those of the French school, 

 whether insects can properly be said to have a 

 circulation of the blood; and whether they have 

 any organ that can properly be called a heart. 



