418 INSECTIVORES. 



of a bright brown colour ; the teeth of Sorex proper, as the common 

 Shrew {8. araneus), are not so stained. (1) 



In the progress of the formation of the large notched incisors, 

 the summits of the tubercles are first formed as detached points, 

 supported upon the common pulp, and do not coalesce until the 

 centripetal calcification has converted the pulp into a common 

 dentinal base. Some anatomists have regarded the large incisor so 

 formed as an aggregate of two or three teeth : but in Sorex proper 

 and Hydrosorex, the calcification of the lower incisor spreads from 

 a single point ; and the interpretation of the notched incisor of the 

 Amphisorex, as the representative of these incisors, (2) might, by 

 parity of reasoning, be applied to the human incisor teeth, the 

 dentated margins of which are likewise originally three or four 

 separate tubercles. 



The determination of the small teeth between the large anterior 

 incisors and the multicuspid molars depends upon the extent of 

 the early anchylosed intermaxillaries ; the incisors being defined 

 by their implantation in those bones, the succeeding small and 

 simple-crowned molars must be regarded as premolars, not any 

 of them having the development or office of a canine tooth ; their 

 analogues in the lower jaw are implanted by two roots. 



The thickness of the enamel in proportion to the body of dentine 

 is unusually great in these small Insectivora, and the sharp points of 

 the teeth long retain their fitness for the office of cracking and crushing 

 the hard or tough teguments of insects. The capsule supporting the 

 enamel-pulp of the lower incisors is so large as to overlap, in the 

 young Shrew, the growing margin of the socket, so as to encase 

 with enamel and cement, not only the crown of the tooth, but also 

 the contiguous part of the jaw-bone. 



Daubenton first drew attention to the close adhesion of the 

 teeth of the Shrews to the jaw-bone ; and M. Duvernoy in his 

 excellent Memoir on these small Insectivores(3), affirms that the roots 



(1) See the beautiful Monograph "Sur les Musaraignes," by Prof. Duvernoy, in the 

 Memoires de la Societe d'Histoire Naturelle de Strasbourg, 4to. 1834. 



(2) See Prof, de Blainville, " Osteographie des Insectivores, p. 55. 



(3) Loc. cit., 4to. 1834. 



I 



