as indicative of the A(je of the Animal. 
297 
larger size, and analogous in every respect to those which have 
been called the Haversian canals in ordinary bone. Fig. 9 gives 
a view of the crnsta within the enamel cup of the incisor of the 
horse, in which such canals abound. The illustration also shows 
the terminations of the dentinal tubes around tlie cup. The letter 
c applies to the crusta as a whole ; c** to the Haversian canals ; 
and c* to a series of cells which are in direct contact with the 
enamel ; d to the dentine ; d* to the dentinal lacuna? ; and K to 
the enamel, which it will be noticed is thickly travei'sed with 
tubes passing from the dentinal lacunae to the cells in the crusta. 
It is a somewhat singular circumstance that the crusta filling: 
these enamel cups, invariably has more numerous Haversian 
canals and fewer canaliculi than that covering the fangs. Com- 
pare fig. 9 with fig. 11. 
Fig. 9* 
c. 
* Fig. 9. Vertical section of the enamel cup of the incisor of the horse, filled with 
crusta and bounded by the dentinal tubes ending in lacunse, from which tubuli are 
seen to pass through the enamel to the crusta. c, crusta; c**, Haversian canals 
in the crusta ; c*, cells lying in apposition with the enamel ; D, dentine ; D*, dentinal 
lacuna;; e, the enamel. Magnified 100 diameters. 
