TEE DOCILE MAMMALS. 



249 



metres (76 feet) in length. The largest of all whales, as of 

 all existing animals, is the fin-back (Fig. 348) or rorqual 

 (Balcennptera hoopfi), which sometimes measures thirty-four 

 metres in length. The smallest Cetacea are the porpoises. 

 In the whalebone whales (Fig. 247) the teeth, present in 

 the embryo, become reabsorbed into the gums before birth 



^ 



Fig. S48.— Fin-whale. 



and are replaced by plates of whalebone, three hundred of 

 which may be present on each side of the mouth. The in- 

 ner edges of these plates have projecting fibres, forming a 

 rude strainer; these whales feed on small pelagic jelly-fish, 

 mollusks, and Crustacea, by taking in a mouthful of water, 

 and then pressing the tongue against the roof of the mouth, 

 expelling the water through the openings between the 

 the fibres acting as a strainer. Three thousand five 



Fio. 249.— Outline of the Cachalot, showing how the blubher is removed, b. the 

 situation of the " case;" c, the junk; ci, the bunch of the neck; h, the hump; /, 

 the ridge; fc, the small; /, the tall or flukes; between the oblique dotted Imes 

 are the spiral strips or blanket pieces. 



hundred pounds of whalebone have been obtained from a 

 single bow-head or Greenland whale (Balcsna mysticetus). 



The cachelot or sperm-whale {Physeter macrocephalus, 

 Fig. 248) has an enormous head, and is without the power 

 of smell. In the upper jaw are cavities filled with a fatty 

 fiuid called spermaceti, used in the manufacture of candles, 

 ointments, and cosmetics, such as cold cream. A large 



