36 



The antero-posterior extent of the alveolar border is 9 inches (Plate XVI. fig. 1). 

 The first socket is irregularly four-sided, the front side being the shortest, slightly 

 convex, and with the angles rounded off between it and the outer and inner sides : 

 the outer side forms rather an acute angle with the hinder side. The area of the 

 second socket is more regularly quadrate, with the transverse diameter the longest; 

 that of the third socket is nearly a true square ; the fourth and last is similar to, but 

 smaller than, the first, with the shortest and most curved side at the back part, and 

 with the antero-posterior diameter a little exceeding the transverse one. The inter- 

 vals between the alveoli are narrow and subequal. 



The rami of the jaw are blended together at the symphysis, which is of great extent, 

 Plate XII. fig. 2, Plate XVI. fig. \,d,d: it begins posteriorly at the fore-part of 

 the mandibular convexity, opposite the second alveolus, whence the symphysis 

 rapidly contracts to the shape of a scoop or spout, which is prolonged 8^ inches 

 from the alveolar part, and terminates in a thick, rough, rounded and emarginate 

 extremity : the canal at the upper part of this spout-like symphysis is semicylindrical, 

 slightly bent down at the end, and 3 inches in diameter ; it becomes roughened by 

 numerous small vascular impressions near the end, but elsewhere is smooth, and has 

 obviously served for the support, during acts of protrusion and retraction, of a long 

 cylindrical tongue. The margins of the canal are thick and rounded. The 'mental 

 foramina,' or anterior outlets of the dental canal (Plate XVI. fig. 2,g), are two on the 

 right side and three on the left, from 4 lines to 8 lines in diameter. 



§ 5. Of the Teeth. 



The teeth are of one kind, molars, five on each side of the upper jaw (Plate XV. 

 and Plate XVII. fig. 2, i,ii,iii,iv,v), four on each side of the lower jaw (Plate XVI. 

 fig. 1, Plate XII. fig. 2, i, ii, Hi, iv), eighteen in total number. 



In the upper jaw, the first or anterior molar (/) is the second in point of size, the 

 last (v) being the least. The first molar (Plate XVII. fig. 2, i) is 8^ inches in length'; 

 the pulp-cavity extends six inches from the base ; it presents two slight curvatures, 

 one having the convexity turned forward, and the other inward. The transverse 

 section (Plate XV. i) gives an irregular semicircle, with the convexity turned for- 

 ward, and the flat side next the second tooth ; the angles at which this side joins the 

 curve are rounded ; the outer angle is somewhat produced, and the outer side of the 

 curve is flattened. The central axis of the tooth, formed by the vaso-dentine *, is 

 irregularly tetragonal ; the cement is thick on the anterior and posterior surfaces, 

 thin on the sides of the tooth. 



The second molar (Plate XV., Plate XVII. fig. 1 & fig. 2, ii) is the largest of the 

 upper series ; it exceeds 9 inches in length, is of a tetragonal form, with two slight 

 curvatures, as in the first molar. The posterior and broadest side is nearly flat, the 



* See my ' Odontography,' and Art. Tbbth in ' Cyclopaedia of Anatomy,' vol. iv. for the definition of the 

 different dental tissues. 



