450 QUADRUMANES. 



of the skull. The capacity of the cranial cavity undergoes no change;^ 

 but the parietes are thickened, especially at the line of the lambdoidal 

 suture, preparatory to the development of the great occipital ridge, 

 which diverges from the end of the sagittal crest. The zygomatic 

 arches are strengthened and expanded, the superior maxillaries 

 produced, while the intermaxillaries having given passage to the 

 crowns of the large permanent incisors, appear to have fallen in. 

 In the Orang the intermaxillary bones at this period have become 

 anchylosed to the maxillaries : in the Chimpanzee that confluence 

 is completed before the deciduous teeth are in place. 



The microscopic structure of the teeth of the Quadrumana 

 is conformable throughout the platyrhine and catarhine groups, 

 and closely resembles that which Purkinje, Retzius, Miiller, and 

 myself have described in the Human subject. As this structure 

 will be more particularly elucidated in the chapter on the Human 

 teeth I shall here merely mention the most obvious differences 

 which the teeth of the Quadrumana present, and which are mani- 

 fested not only in the Baboons and Monkeys but in the most 

 anthropoid Ape, viz : the Chimpanzee(l). In the incisor and canine 

 the general direction of the calcigerous tubes agrees with that figured 

 in Fraenkel's Thesis, fig. 1, B, and by Retzius in his " Mikros- 

 kopiska undersokningar" PI. i (iv), fig. 1, in the corresponding Human 

 teeth. The tubes(2) in the Chimpanzee describe the same primary 

 curvatures, but less strongly ; and the secondary gyrations are 

 longer and more feebly marked : they are jio^h of an inch in dia- 

 meter, and the interspace between two tubes on the same plane 

 equals the width of two tubes, when viewed in transverse section 

 near the pulp-cavity, as in PL 119a, fig. 2; nearer the enamel the 

 interspaces are wider ; but in general they are more closely arranged 

 and relatively more numerous, besides being straighter than in the 

 Human subject. They maintain the same diameter through three- 

 fourths of their course ; divide sparingly, except close to the enamel 

 boundary and the periphery of the fang : in this part of the tooth 

 the minute lateral branches are most numerous. The calcigerous cells 

 of the dentine(3) are most conspicuous, as usual, near the periphery 

 of the crown, where their well-defined semi-circular contour is seen 

 (1) PI. 119 0, fig. 1 & 2. (2) lb. fig. 1, t. t. (3) lb. fig. 1, d-, d: 



