620 



The tooth relationships in the Rabbit have long been known and 

 are well and correctly described by Cuvier *) and later by Owen 2 ). 



Cuvier further added to our knowledge of the milk dentition of 

 the Rodentia by the discovery of the single milk premolar on either 

 side of the upper and lower jaw of the Guinea Pig, which though 

 fairly well developed never becomes functional and is shed in utero. 



For a considerable period after these discoveries no further light 

 was brought to bear on this problem, in fact the subject was thrown 

 into great confusion by many authors who mixed up the milk and 

 permanent incisors of the Rabbit in such a hopeless way that we 

 still find this animal described in many text books as possessing 

 three permanent upper incisors. 



In 1880, Huxley 3 ) in a foot-note to a paper on Mammalia de- 

 scribed the presence of a pair of minute theeth in the upper and 

 lower jaw of the Rabbit, these he considered as representing the milk 

 predecessors of the large incisors. This note has not unnaturally 

 escaped the observation of subsequent writers, but there can be no 

 doubt that he was the first to discover the existence of these teeth 

 and although he did not work out the detailed relations of their 

 enamel organs to those of the four large incisors, he, nevertheless 

 rightly interpreted them as the vestigies of the milk predecessors to 

 the large incisors of the adult. 



In 1884, Pouchet and Chabry 4 ) without being aware of Hux- 

 ley's work, rediscovered these minute teeth and studying them by 

 means of sections they demonstrated their relations to the four 

 large incisors. They also described in detail the development of the 

 milk 2nd upper incisor and its successor. In the Rat and Squirrel 

 which they studied, they were unable to find any trace of vestigial 

 incisors similar to those seen in she Rabbit. 



Lataste 5 ) in 1888, referring to Pouchet and Chabry, states 

 that all the Duplicidentata have their incisors preceeded by milk teeth 

 or are as he terms it "Diphysaire", while the Simplicidentata are 

 "Monophysaire", or devoid of milk incisors. 



1) Cuvieb, Ossements fossiles. 



2) Owen, Comparative Anatomy and Physiol, of Vertebrates, vol. 3, p. 300. 



3) T. H. Huxley, On the Application of the Laws of Evolution to 

 the Arrangement of the Vertebrata and more particularly of the Mam- 

 malia. Proc. Zool. Soc, 1880, footnote p. 655. 



4) Pouchet and Chabky, Contributions ä l'odontologie des Mammi- 

 feres. Jour. Anat. et Physiol., 1884, p. 147. 



5) J. Lataste, Des dents exceptionellement monophysaires chez les 

 Mammiferes diphyodonts. Comp. Rend. Soc. Biol. (8) V, p. 37 — 41. 



