574 MANUAL OF ZOOLOGY. 



Whale often applied to it. It is an inhabitant of the Arctic 

 seas, and reaches a length of from forty to sixty feet. Of this 

 enormous length, nearly one-third is made up of the head, so 

 that the eye looks as if it were placed nearly in the middle of 

 the body. The skin is completely smooth, and is destitute of 

 hairs in the adult. The fore-limbs are converted into " flip- 

 pers " or swimming-paddles, but the main organ of progression 

 is the tail, which often measures from twenty to twenty-five 

 feet in breadth. The mouth is of enormous size, the upper 

 jaw somewhat smaller than the lower, and both completely 

 destitute of teeth. Along the middle of the palate runs a 

 strong keel bordered by two lateral depressions, one on each 

 side. Arranged transversely in these lateral depressions are 

 an enormous number of horny plates, constituting what is 

 known as the " baleen " plates, from which the whalebone of 

 commerce is derived. The arrangement of the plates of baleen 

 is somewhat as follows (fig. 245) : Each plate is somewhat 

 triangular in shape, the shortest side or base being deeply 

 sunk in the palate. The outer edge of the plate is nearly 

 straight, and is quite unbroken. The inner edge is slightly 

 concave, and is furnished with a close fringe formed of detached 

 fibres of whalebone. For simplicity's sake each baleen-plate 

 has been regarded here as a single plate, but in reality each 

 plate is composed of several pieces, of which the outermost is 

 by far the largest, whilst the others gradually decrease in size 

 towards the middle line of the palate. The large marginal 

 plates are from eight to ten or fourteen feet in length, and 

 there may be about two hundred on each side of the mouth. 



The object of the whole series of baleen-plates with which 

 the palate is furnished, is as follows : The Whale is a strictly 

 carnivorous or zoophagous animal, but owing to the absence 

 of teeth, and the comparatively small calibre of the oesophagus, . 

 it lives upon very diminutive animals. The Whale, in fact, 

 lives mostly upon the shoals of small Pteropodous Molluscs, 

 Ctenophora and Medusa, which swarm in the Arctic seas. To 

 obtain these, the whale swims with the mouth opened, and 

 thus fills the mouth with an enormous mass of water. The 

 baleen-plates have the obvious function of a "screening-appa- 

 ratus." The water is strained through the numerous plates of 

 baleen, and all the minute animals which it contains are ar- 

 rested and collected together by the inner fibrous edges of the 

 baleen-plates. When, by a repetition of this process, the 

 Whale has accumulated a sufficient quantity of food within the 

 central cavity of the mouth, it is enabled to swallow it, with- 

 out taking the water at the same time. 



