70 MEMOIRS OF 



sometimes there is only one of these two parts. 

 In the first case, the two hearts, or, rather, the 

 two ventricles, may be united in one single mass, 

 as in man, mammalia, and birds ; or they may 

 be separated, as in the cuttle-fish. When there 

 is only one ventricle, it is either placed at 

 the base of tlie artery of the body, as in snails 

 and other mollusca, or at the base of the pul- 

 monary artery, as in fislies. 



** The organs of respiration are equally fertile 

 in remarkable differences. When the element 

 which is to act on the blood is the atmospheric 

 air, it penetrates even into the interior of the 

 respiratory organ ; but, when it is water, it 

 simply glides over a surface, more or less mui- 

 tijilied. These surfaces, or leaflets, are called 

 branchiag, and are found in fishes, and many of 

 the mollusca. Instead of leaflets, there are 

 sometimes tufts, or fringes. Air penetrates into 

 the body by one or several orifices. In the first 

 instance, which is that of all animals with lungs, 

 properly so called, the channel which receives 

 the air is subdivided into a multitude of branches, 

 which terminate in as many little cells, generally 

 collected into two masses, which the animal has 

 the power of compressing or dilating. When 

 there are several openings, which we see only in 



