VOL. LXXVII.] PHILOSOPHICAL TRANSACTIONS. 325 



In the piked whale, when the mouth is shut, the projecting whalebone re- 

 mains entirely on the inside of the lower jaw, the two jaws meeting every 

 where along their surface ; but how this is effected in the large whale I do not 

 certainly know, the horizontal plane made by the lower jaw being straight, as 

 in the piked whale ; but the upper jaw, being an arch, cannot be hid by the 

 lower. I suppose therefore that a broad upper lip, meeting as low as the lower 

 jaw, covers the whole of the outer edges of the exterior rows. The whalebone 

 is continually wearing down, and renewing in the same proportion, except that 

 when the animal is growing it is renewed faster, and in proportion to the 

 growth. 



The formation of the whalebone is extremely curious, being in one respect 

 similar to that of the hair, horns, spurs, &c. ; but it has besides another mode 

 of growth and decay, equally singular. These plates form a thin vascular 

 substance, not immediately adhering to the jaw-bone ; but having a more dense 

 substanqe between, which is also vascular. This substance, which may be 

 called the nidus of the whalebone, sends out the above thin broad processes, 

 answering to each plate, on which the plate is formed, as the cock's spur or the 

 bull's horn, on the bony core, or a tooth on its pulp ; so that each plate is ne- 

 cessarily hollow at its growing end, the first part of the growth taking place on 

 the inside of this hollow. Besides this mode of growth, which is common to 

 all such substances, it receives additional layers on the outside, which are formed 

 on the above-mentioned vascular substance extended along the surface of the 

 jaw. This part also forms on it a semi-horny substance between each plate, 

 which is very white, rises with the whalebone, and becomes even with the outer 

 edge of the jaw, and the termination of its outer part forms the bead above- 

 mentioned. This intermediate substance fills up the spaces between the plates 

 as high as the jaw, acts as abutments to the whalebone, or is similar to the 

 alveolar processes of the teeth, keeping them firm in their places. 



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 depending entirely on chance, or the use it is put to. 

 In its growth, 3 parts appear to be formed ; one from the rising core, which is 

 the centre, a 2d on the outside, and a 3d being the intermediate substance. 

 These appear to have 3 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 pro- 

 jecting, becoming at the termination very brittle ; and the 3d, or intermediate 

 substance, by the time it rises as high as the edge of the skin of the jaw, decays 

 and softens away like the old cuticle of the sole of the foot when steeped in 

 water. The use of the whalebone, I should believe, is principally for the re- 



