EXPLANATION OF THE PLATES. 



PLATE XXXVI. 



STRUCTURE OF TEETH. 



Fig. 1. Vertical section of incisor tooth magnified with a 

 lens only, and showing the three constituents of 

 which every human tooth is composed, viz., supe- 

 riorly the enamel, inferiorly the cementum, and in 

 the centre the dentine, traversed in the midst by 

 the medullary cavity. 



2. Tubes of the dentine, showing their ordinary mode 



of termination in connection with the cementum, 

 magnified 670 diameters. 



3. A not unfrequent condition of the tubes of the den- 



tine, showing their repeated division, and their con- 

 nection with bone cells near their termination. 670 

 diameters. 



4. Tubes of the dentine near their commencement from 



the pulp cavity seen lengthways : one of the tubes 

 may be observed to divide in a dichotomous man- 

 ner. 670 diameters. 



5. Oblique section of tubes of the dentine. 



6. Transverse section of ditto. 



7. Displays the breaking up of the tubes of the dentine 



into bone cells: this occurs principally near the 

 terminations of those tubes which pass towards the 

 cementum, and not of those which run towards the 

 enamel: this condition does not present itself in 

 every tooth. 670 diameters. 



8. Tubes of the dentine midway between their origin 



and their termination, dilated into bone cells. 670 

 diameters. This figure is taken from a specimen 

 kindly lent me by Mr. Tomes. 



