118 UNIVERSALITY OF DEGENERATIVE EVOLUTION 



According to Hertwig, the teeth should be 

 regarded as part of the tegumentary system, as 

 they really represent the scales of the skate, 

 situated within the buccal cavity. 



In man, the last molar, or wisdom tooth, is a 

 rudimentary tooth. The small- sized shallow crown, 

 the diminished number of tubercles, the fusion of 

 the roots, the tardy appearance and occasional 

 absence altogether, are all indications of a rudi- 

 mentary condition. 



2. The Skeleton. With few exceptions, the 

 articular surfaces of the bodies of mammalian 

 vertebrates are covered in youth with bony 

 plates. These sometimes become very thick, and 

 are called terminal epiphyses. In some mammals 

 the Sirenians, for instance the terminal epi- 

 physes have disappeared. In man they still 

 exist, but in an advanced stage of degeneration. 

 In the lower vertebrates, such as the crocodile, 

 many more ribs are functional than in man. 

 In the crocodile all the ribs connected with the 

 cervical vertebrae are functional, whereas in man 

 they have degenerated. Of one entire section of 

 the human vertebral column the tail so fully 

 developed in the majority of other vertebrates, 

 only a vestige now remains. 



Other rudimentary skeletal pieces are the lesser 

 horn of the hyoid bone, the stylo-hyoidean liga- 

 ment, the coracoid process, and the interclavicular 

 ligament. 



