422 INSECTIVORES. 



numerous minute branches. As the tubes become situated lower 

 down the fang the number of their large curved lateral branches 

 becomes more remarkable ; and the reticulate or moss-like disposi- 

 tion extends over a greater proportion of the dentine. Numerous 

 minute opake cells form the boundary line between the dentine and 

 the cement which covers the fang. The minute transverse tubuli 

 of the cement are present in the thinner part, where there are no 

 Purkinjian cells ; these cells are developed in great number, and 

 present the usual irregular angular figure in the mass of cement 

 closing the end of the fang. 



The enamel fibres are disposed with a very slight curve, almost 

 transversely to the plane of that substance, inclining towards the 

 crown ; they are crossed by other lines nearly parallel with the same 

 plane, extending from its inner surface upwards and outwards ; these 

 lines are equi-distant, parallel with each other, with intervals equal 

 to the breadth of two enamel fibres ; they indicate successive and 

 regular periods in the formation of the enamel ; and, where they 

 crop out upon the outer surface of the enamel, they form the fine 

 transverse striae which have been often noticed on that substance 

 in larger teeth. I counted sixteen of these longitudinal hnes 

 in a section of the enamel, at the middle of the side of the 

 crown of the incisor examined, where the enamel was g^th of an 

 inch in thickness. 



Not any of the main calcigerous tubes are straight in the molars 

 of the Hedgehog ; those which ascend from the summit of the pulp- 

 cavity to the middle of the grinding surface of the crown, rise with 

 a wavy curve, which becomes stronger in the tubes that diverge to the 

 angles of the crown. At the sides of the crown the tubes curve out- 

 wards, with the concavity turned towards the grinding surface, and 

 then bend towards the enamel in the opposite direction ; the latter cur- 

 vature being lost in the transverse tubuli of the fangs, which have a 

 single curvature convex towards the crown ; near the end of the 

 fang the tubuli bend down with irregular flexuosities, and here they 

 present very conspicuously that rich ramification which Retzius has 

 remarked : it is also beautifully seen in the tubuli of the dentine 

 at the base of the crown between the origins of the fangs. The 



