68 INTERNAL ORGANS. 



the masses of fatty matter which sometimes surround 

 it in considerable quantity, are of the same tint as the 

 fluid within, and it may be, the fluid derives its co- 

 lour from them, though M. Audouin seems to think 

 the reverse is the case. 



Meckel and Herold, considering the organ a 

 heart, think that its beatings, or alternate contraction 

 and dilatation, which affect its whole extent, are for 

 the purpose of agitating, not of circulating, the fluid 

 it contains, as they admit no outlet or inlet by means 

 of vessels for that purpose. Herold thinks that the 

 dilatation, or diastole, is produced by the triangular 

 muscles which attach it to the back ; while the con- 

 traction, or systole, is produced by the muscular fibres 

 of the inner membrane. 



The heart of a carnivorous grasshopper, with its valves, cham- 

 bers, and artery, from M. Audouin. 



"The dorsal vessel," says M Straus-Durckheim, a 

 naturalist of high talent, " is in reality the heart of 

 insects, being in them, as in higher animals, the mover 

 of the blood, which in them, instead of being con- 

 tained in blood vessels, is diffused through the cavity 

 of the body. The heart occupies the whole of the back 

 of the abdomen, and ends at the fore part of the organ 

 in a single artery( 1 ) without branches,which carries the 

 blood into the head where it is poured out, whence it 

 flows back into the abdomen, in consequence solely of 

 its accumulation in the head, in order to enter anew into 



(1) This was anticipated in part by Lyonnet, page 412. 



