WHALES. 315 



his account of the Balmna mysticetus, notices only the large marginal 

 plates, states that they are about two hundred in number on each 

 side : the largest are from ten to fourteen feet, very rarely fifteen 

 feet in length, and about a foot in breadth at their base. These 

 plates are overlapped, and concealed by the under lip when the 

 mouth is shut.(l) In the Balanoptera, or Fin-backed Whales, the 

 baleen-processes internal to the marginal plates, are fewer and smaller 

 than in the BalcBncs : the marginal plates are more numerous^ ex- 

 ceeding three hundred on each side: (2) they are broader in pro- 

 portion to their length, and much smaller in proportion to the 

 entire animal : they are also more bent in the direction transverse to 

 their long axis. 



Each plate of baleen consists of a central coarse fibrous sub- 

 stance, and an exterior compact fibrous layer : but this reaches to 

 a certain extent only, beyond which the central part projects in 

 the form of the fringe of bristles. John Hunter first expressed 

 a belief, that the part of the baleen, which was formed by the 

 core or pulp was the hair : and that this received the compact 

 layers on the outside, from the dense but vascular substance be- 

 tween the bases of the plates ; which substance he well describes 

 to act as abutments to the whalebone, like the alveolar processes 

 of the teeth, keeping them firm in their places. And he further 

 observes : "As both the whalebone and intermediate substance 

 are constantly growing, and as we must suppose a determined length, 

 necessary, a regular mode of decay must be established, not depend- 

 ing entirely on chance, or the use it is put to. In its growth three 

 parts appear to be formed ; one from the rising core, which is the 

 centre ; a second on the outside ; and a third being the intermediate 

 substance. These appear to have three stages of duration ; for that 

 which forms on the core, I believe, makes the hair, and that on the 

 outside makes principally the plate of whalebone ; this, when got 

 a certain length breaks off, leaving the hair projecting, becoming 

 at the termination very brittle ; and the third or intermediate sub- 

 stance, by the time it rises as high as the edge of the skin of the 



(1) Wernerian Trans : vol. i. p. 579. 



(2) Hunter, loc. cit. p. 307, & Neill, Wernerian Trans, vol. i. p. 202. 



