CETACEA. 245 



to be short and flattened, yet distinct and handlike ; but the whole 

 of this osseous frame-work is enveloped in a cartilaginous cover, 

 ing, so as to form an undivided oar. The chief use of the pad- 

 dies seems to be that of balancing the animal, for as soon as life 

 is extinct, it falls over upon its back; they are also employed in 

 turning and giving direction to the velocity produced by the tail. 



The Cetacea regularly resort to the surface to take in a fresh 

 supply of air. They also descend into the remotest depths of the 

 ocean ; in the case of the larger animals sometimes encountering 

 a pressure which has been estimated at two hundred thousand 

 tons, or one hundred and fifty times as great as that of the atmos 

 phere, and sufficient to force water through the hardest wood, 

 causing it to sink like so much lead. For sustaining so vast a 

 pressure, their structure is most wisely adapted. 



The body is covered with a coat of peculiar elasticity. The 

 naked skin is itself much thickened; but by an open texture of 

 its interwoven fibres, it is made to contain within itself, a thick 

 layer of oil or blubber, and thus the animal can endure, without 

 injury, the greatest weight of water. &quot;A soft wrapper of fat, 

 though double the thickness of that usually found in the Cetacea, 

 could not have resisted the superincumbent pressure ; whereas, 

 by its being a modification of the skin, always firm and elastic, 

 and in this case, being never less than several inches, and some- 

 times between one and two feet thick, it operates like so much 

 india-rubber, possessing a density and resistance which, the more 

 it is pressed, resists the more.&quot;* As the blubber is specifically 

 lighter than water, it also makes the animal more buoyant. A 

 dead whale floats ; but the body, when stripped of its fat, sinks 

 immediately. Another important use of the blubber, is to pre 

 serve the vital heat of the body in a cold medium, which has a 

 constant tendency to abstract caloric. Without this layer of 

 blubber, which is one of the worst conductors of heat, the whale 

 would be unable to resist the low temperature of the Arctic Seas, 

 and must perish from cold. The eyes of the Cetacea are admi 

 rably adapted to the dense medium in which the animals dwell. 

 As compared with the size of the body, the eyes are small, 

 generally not larger than those of an ox ; in the Beluga, or 

 White Whale, they are smaller than the human eye; in the Por 

 poise, not so large as those of a sheep. In the Cetacea, &quot;the 

 humours of the eye are so adjusted in their form, density and 

 refractive power, as to prevent any dispersion, or decomposition 

 of the rays.&quot; The refractive power of the aqueous humor, 



* Naturalist s Library. Mammalia, VII., 48. 



