140 Lectures on the Results of the 



bears to the tooth. According to these analogies, it must follow 

 that the only central fibrous or tubular portion of the baleen plate 

 is formed, like the dentine, by the basal pulp, and that the base of 

 the plate is not only fixed in its place by the cementing substance 

 or capsule, but must also receive an accession of horny material 

 from it. 



The baleen plates are smallest at the two extremities of the 

 series ; in the southern whale {Balcena Australis) they rapidly in- 

 crease in length to the thirtieth, then very gradually increase in 

 length to about the one hundred and fortieth ; from this they as gra- 

 dually diminish to the one hundred and sixtieth plate, and thence 

 rapidly slope away to the same small size as that with which the 

 series commenced. Besides the external, and, as they may be 

 termed, the normal plates, which have just been described, there 

 are developed from the inner part of the palatal gum, in the 

 Balcena Australis, a series of smaller fringed processes, progres- 

 sively decreasing in size as they recede from the large external 

 plates ; the small plates clothe the middle region of the palate 

 with a finer kind of hair, against which the surface of the tongue 

 more immediately rests ; they are also arranged in longitudinal 

 series, which, however, are not parallel with the external one, but 

 pass from the inner margin of that series in oblique lines inwards 

 and backwards. 



In the great northern whale, (Balcena mysticetus), the baleen 

 plates which succeed the large ones of the outer row are more nu- 

 merous, and are relatively longer and larger than in the Balcena 

 Australis. Mr Scoresby, who, in his account of the Balcena mys- 

 ticetus, notices only the 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. In the 

 Balcenopterce, or fin-backed whales, the baleen processes, internal 

 to the marginal plates, are fewer and smaller than in the true 

 whales (Balcence.) The marginal plates are more numerous, ex- 

 ceeding three hundred on each side ; they are broader in propor- 

 tion 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 the baleen consists of a central coarse fibrous 

 substance, 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. The chemical basis of baleen, 

 according to the experienced Professor Brande, is albumen, har- 

 dened by a small proportion of phosphate of lime.* 



* " For the microscopical characters, and other particulars of the haleen plates, 

 I must refer to my Od<intoarni>hy, vol. i., p. 311.'" 



