630 



THE EXTERIOR OF THE HORSE. 



On the internal face, I, the grooves are more numerous: in the first and 

 sixth three are observed ; in the other molars several grooves of variable length 

 and depth are seen. 



E. External face. 



FIG. 299. Inferior molar of the second 



dentition. 



(Left side. Virgin tooth.) 

 | /. Internal face. | E, I. Surface of friction. 



Extremities. The free extremity, El, triangular in the first and sixth, 

 and quadrilateral in all the others, is less extensive transversely than from before 

 to behind. Irregularly mammillated, elevated at some points and hollow at 

 others, it is always bevelled obliquely from within to without. The branches of 

 the Gothic 53 are turned outward. 



The incased extremity, bicuspid in the first five, is unicuspid in the sixth. 

 The divisions of the root are divergent, and each contains an opening which 

 penetrates the interior of the tooth where the dental pulp is lodged. 



Length. The length increases from the first to the third, and diminishes 

 from the latter to the sixth. Below are the measurements which we have ob- 

 tained from the teeth of the head previously mentioned : 



1st 0.044 m., plus the posterior root, = 0.018 m. = 0.062 m. 



2d 0.063m., " " " = 0.015 m. = 0.078 m. 



3d 0.078m., " " " = 0.009 m. = 0.087 m. 



4th 0.063m., " " " =0.017 m. = 0.080 m. 



5th 0.067m., " " " = 0.009 m. = 0.076 m. 



6th, which is deprived of roots, has a total length of 0.066 m. 



Direction. After removing the external table of the inferior maxilla in 

 order to expose the teeth, it is easy to recognize that all have not the same direc- 

 tion. Placing the head upon a horizontal plane, the first and sixth are ver- 

 tical, while the others are more oblique, particularly in the incased extremity, as 

 they are examined more posteriorly. 



Relations. The alveoli, which contain the teeth, have a corresponding 

 form, and are separated from each other by osseous septa (interalveolar septa), 

 quite thick, which become thinner towards the entrance of these cavities. 



