ORDER CETACEA; GENERAL CHARACTERS. 239 



tissue (ANIM. PHYSIOL., 44) beneath the skin ; but in the 

 Cetacea it is deposited in the substance of the skin itself, which 

 is of enormous thickness, consisting of elastic fibres interlacing 

 in every direction, in the interstices of which the oil is contained. 

 This substance is commonly known as blubber. The arrangement 

 which has been described appears to serve two purposes; it 

 serves to keep in the heat of the body, which would otherwise 

 be too rapidly carried off by the conducting power of the water 

 in which it floats ; and it enables these animals to sustain the 

 enormous pressure, to which they are subjected, when they sink 

 deep below the surface, a pressure sometimes amounting to a 

 ton upon every square inch. The thickness of this layer of 

 blubber is never less than several inches, and it is sometimes 

 between one and two feet ; its weight not unfrequently amounts 

 to thirty tons ; but being lighter than water, it buoys up the 

 enormous body which it incloses, instead of weighing it down. 

 The remarkable conformation of the circulating apparatus, by 

 which the necessity for frequent respiration is dispensed with, has 

 been elsewhere described (AwiM. PHYSIOL., 265). The act of 

 respiration is facilitated by the position of the nostrils, which are 

 situated nearly at the highest point of the head ; so that the 

 animal can breathe as soon as the head comes to the surface of 

 the water. The Whales have the power of forcing out water 

 through these passages, by means of a peculiar apparatus with 

 which they are provided. This consists of two pouches or reser- 

 voirs, situated beneath the nostrils, and communicating with the 

 back of the mouth by the usual nasal passage, which is furnished 

 with a valve. When the animal wishes to eject water contained 

 in its mouth, it moves its tongue and jaws as if about to swallow 

 it ; but, by closing the pharynx, it compels the water to ascend 

 through the nasal passage, whose valve it forces open, and to 

 distend the reservoirs. There it may be retained, until the 

 animal desires to spout ; and this is effected by a forcible com- 

 pression of the pouches, which compels the water to escape by the 

 nostrils or blow-holes, its return to the mouth being prevented 

 by the valve just mentioned. The aperture of the nostrils is 

 guarded by a conical valve or stopper ; composed of numerous 



