194 



ANIMAL PHYSIOLOGY. 



[LESSON 55. 



FIG. 312. 



FIG. 311. culi, are more than usually 



distinct. 



832. In the figure several 

 very thin transverse sections 

 of the dentine appear, attached 

 to the sides of the pulp cavity 

 (e) ; these exhibit the tubular 

 character of the canals very 

 satisfactorily. 



833. Special reference is made to these thin sections of the tubes 

 as they are ordinarily seen, in another figure (Fig. 311) much more 

 highly magnified, indicating the tubes, and a more crowded con- 

 dition of them in Fig. 312. 



Trnnsvor.*e section of 

 IX-ntinul tubes. 



A raorfi crowded 

 view. 



FIG. 313. 



LESSON LY. 



THE STEUCTUBE OF THE TEETH, CONTINUED. 



834. In the teeth of the Dog the same tissues, arranged on the 

 same plan, are found, and present in the molar teeth a very inter- 

 esting appearance (Fig. 313). The enamel (a) is always distin- 

 guished by its apparent density, as compared with the other tissues , 

 towards the edges of the upper portion of the figure (5), the ter- 

 minal line of the enamel, and the commencement of the crusta pe- 

 trosa, is shown. From this point it (crusta petrosa) can be traced 

 descending the fangs, right and left, to their 

 termination, then ascending, and finally form- 

 ing a junction at the centre. On the inner 

 surface of the enamel, and crusta petrosa, 

 the dentine is seen (c), and within this tis- 

 sue the large, well-formed pulp cavity (d). 

 At the bend, which connects the two fangs, 

 the dentinal tubuli assume a curious and 

 very beautiful arrangement. 



835. The molar tooth of a Cat displays 

 the same arrangement of the like tissues, 

 and the external form of the tooth bears 

 great resemblance to the molar of the Dog 

 (Fig. 314) ; a, the enamel; 5, crusta petrosa ; 

 c, dentine ; and d, pulp cavity. 



Molar Tooth, Dog. 



