INSECTIVORES. 423 



tubes in the crown retain their almost parallel course and their 

 character of undivided trunks, until they attain the usual proximity 

 to the enamel. 



This substance offers no noticeable peculiarity in the molar teeth. 

 The fangs are invested with a layer of cement, which is suffi- 

 ciently thick at their extremities and at the interspace of their origins 

 to show the calcigerous cells ; these cells present an irregular 

 elongated form, with angular projections continued into the radiated 

 tubes. The cement is likewise traversed by transverse minute 

 parallel tubuli of the size of those in the dentine, which have a 

 diameter of ig^th of an inch. 



The deciduous teeth of the Moles and Shrews are uterine, i.e. 

 are developed and disappear before birth ; they are extremely small, 

 and all of the most simple form. In the foetal Sorex araneus cal- 

 cification of the papillary exposed pulps of the teeth which are 

 succeeded by the first and second premolars proceeds to a very 

 slight extent, and these microscopic rudiments appear to be absorbed 

 rather than shed ; the deciduous incisors are further advanced before 

 their displacement, and present the form of equal-sized dentinal 

 spicula, tipped with enamel, attached by the opposite end to the 

 gum, and not exceeding ^^th of an inch in length ; the number of 

 the uterine series of teeth is Ie*. 



In a foetal Hedgehog, two inches and a half in length, the alveolar 

 border of the upper jaw forms a smooth, convex ridge on each side, 

 and those of the lower jaw are equally entire and edentulous, but less 

 prominent ; both are covered by a thick epithelium ; the margin 

 of the gum easily opens longitudinally, as if the dentiparous groove 

 had been but recently closed, and the matrices of five deciduous teeth 

 on each side are brought into view ; the four first, representing the 

 three incisors and the canine, are very minute and simple, the fifth 

 tooth is quadrituberculate, and g^th of an inch in breadth : calcification 

 has commenced in the summits of the crown of this deciduous tooth, 

 which is succeeded by permanent premolars of a more simple form. 

 M. Duvernoy alludes to M. Laurillard's examination of the deciduous 

 teeth of the Hedgehog, and states that he has himself determined 

 their existence in the Tenrecs (Centetes), in which they are long 



