330 



VERTEBRATE ANIMALS. 



under the skin, and serves to protect the body from cold. Though 

 an inhabitant of the sea, the Whale is obliged to come to the surface 

 to breathe, and in so doing it ejects from the blow-hole what looks 

 like a column of water, the whole operation being known to the 

 whalers as " blowing." The true nature of this act is now hardly 

 questionable, and it appears certain that the apparent jet of water 

 is in reality, mainly if not entirely, due to the condensation of the 

 moisture which is contained in the air expelled from the lungs. 

 The old view was that " blowing " consisted in the Whale ejecting 

 througli the nose the water which had previously been filtered 

 through the baleen-plates of the mouth ; but it ajjpears to be quite 

 certain that this view, at any rate, is not the correct one. The 

 Rorquals or Finner Wliales resemble the Greenland Whale in most 

 respects, but the skin is f nrrowed with deep plaits or folds, and there 

 is a dorsal fin, placed on the back. Some of these attain a gigantic 



Fig. 236. — Cetacea. The coimnon Doli)hin (Delphinus delpliis). 



size (eighty feet or more), but they are seldom captured, as their 

 commercial value is small. 



The Toothed Whales (Odoiitorrti) are best known by the Sperm 

 Whale (fig. 23.")), an animal as large or larger than the tireenland 

 Whale, but distinguished by having numerous conical teeth, a single 

 blow-hole, and a curiously truncated head. Sperm Whales yield 

 an excellent oil, and the singular fatty siibstance which is known as 

 "spermaceti." They also yield the substance called "ambergris," 

 which is used as a perfume ; but this is probabl}- a product of disease. 



The last family of the Cetacen needing mention is that of the 

 Delphiiiiihe, comprising the Dolphins (fig. 236) and Porpoises. They 

 have numerous conical teeth in both jaws, and the nostrils open by 

 a single aperture on the top of the head. The Dolphins are mostly 

 inhabitants of the sea, but there are fresh-water forms which inhabit 

 the rivers of South America and Southern Asia. The Porpoises are 

 exclusively marine, and occur in all seas. Tlie most remarkable of 

 the Drl phiiiidce is the Narwhal or Sea-unicorn, which is found in 



