PORPESSE. 



15 



Vertebrates, the mammalia being the highest, 

 and the fish the lowest. 



Some people say, that as it looks like a fish, 

 and lives like a fish, to all intents and purposes 

 it is a fish. So it is, if the diver at the Poly- 

 technic Institution is a fish ; for it holds its lease 

 of life on precisely the same tenure. Both diver 

 and porpesse must breathe atmospheric air, or 

 they would die; and therefore each finds means 

 to supply himself with that indispensable 

 material. The diver surrounds himself with a 

 supply of fresh air, with which to renovate his 

 blood; but the porpesse is able to renovate a 

 surplus amount of blood, that lasts him for some 

 time : so the chief difierence is, that the diver 

 takes down with him oxygen externally, and the 

 porpesse internally. The man goes down inside 

 the diving-bell, but the diving-bell goes down 

 inside the porpesse. 



Yet the porpesse has no reservoir in which 

 atmospheric air is retained, for such a formation 

 would make it too buoyant. There is, however, 

 in the cetacece, to which family the porpesse 

 belongs, a reservoir of blood, which is renovated 

 by the atmospheric air, and is passed into the 

 system as required. Even man has the same 

 power, although in a limited degree. In general. 



