18 ALES' HRDLIKA 



If there are any exostoses on the border they are to be avoided by 

 placing the points of the instrument above the same. The measure- 

 ment to be taken is the maximum transverse separation of the alveolar 

 borders. 



(6) Length of the alveolar arch; e.g. (F, fig. 4). 



Landmarks: Anteriorly the anterior surface of the alveolar border 

 between the two median incisors; posteriorly the middle of a trans- 

 verse line connecting the posterior extremities of the alveolar border. 



[This transverse line is obtained easily by placing a wire as deep as 

 possible on each side in the notch which separates the alveolar border 

 from the pterygoid process.] 4 



19. The bony palate: e.g. (optional), 

 (a) Length of the palate (L, fig. 4). 



Landmarks: Anteriorly the median point of a line tangent to the 

 posterior alveolar border of the median incisors; posteriorly the me- 

 dian point of a transverse line connecting the most anterior points of 

 the notches in the posterior border of the palate. 



(6) Breadth of the palate. 



Distance between the [internal] alveolar borders between the sec- 

 ond molars. 



20. Orbito-alveolar height; e.g. (optional). 



The minimum distance between the lower border of the orbit and 

 the alveolar border. 



21. Foramen magnum; e.g. 

 (a) Length. 



Landmarks: Anteriorly the basion; posteriorly the opisthion, or 

 median point of the posterior border. 



(6) Breadth. 



Landmarks: Points of maximum separation, in transverse line, of 

 the lateral borders of the foramen. 



22. Sagittal arc of the vault; m.t. 



Landmarks: Anteriorly the nasion; posteriorly the opisthion. 

 Intermediary: Apply tape to the surface of the vault along the sag- 

 ittal line. 



The arc is divisible into three principal parts which should be re- 

 corded separately and which correspond to the three bones composing 

 the vault, namely the frontal, parietal and occipital. 

 4 The maxillo-alveolar index will be: 



Maximum breadth of the alveolar border X 100 

 Length of the alveolar arch 



