124 THE VITAL FUNCTIONS. 



of the ocean ; and which has been already deli- 

 neated in Fig. ]20.* 



These remarkable organs for filtration entirely 

 supersede the use of ordinary teeth ; and accord- 

 ingly no traces of teeth are to be discovered either 

 in the upper or lower jaw. Yet a tendency to con- 

 form to the type of the mammalia is manifested in 

 the early conformation of the whale ; for rudiments 

 of teeth exist in the interior of the lower jaw before 

 birth, lodged in deep sockets, and forming a row 

 on each side. The developement of these imper- 

 fect teeth proceeds no farther ; they even disappear 

 at a very early period, and the groove which con- 

 tained them closes over, and after a short time can 

 no longer be seen. For the discovery of this cu- 

 rious fact we are indebted to GeofFroy St. Hilaire.t 

 In connexion with this subject, an analogous fact 

 which has been noticed in the Parrot may here be 

 mentioned. The young of the parrot, while still 

 in the egg, presents a row of tubercles along the 

 edge of the jaw, in external appearance exactly 

 resembling the rudiments of teeth, but without 

 being implanted into regular sockets in the maxil- 

 lary bones : they are formed, however, by a process 

 precisel}^ similar to that of dentition ; that is, by 

 deposition in the cells of avascular pulp, connected 

 with the jaw. These tubercles are afterwards conso- 

 lidated into one piece in each jaw, forming by their 

 union the beak of the parrot, in a manner perfectly 

 analogous to that which leads to the construction 

 of the compound tooth of the elephant, and which I 



* Vol. i. p. 231. 



t Cuvier, Ossemens Fossiles, 3me edition, torn. v. p. 360. 



