168 MAMMALIAN DENTITION 



the zygoma is not directly connected with the state of the den- 

 tition and it must therefore be ignored in our present survey. 

 In spite of the relative smoothness of the Sloth's skull care- 

 ful observation shows that although the occiput slopes upward 

 and forward and does not display powerful muscular impres- 

 sions the masticatory muscles are quite well developed. The 

 area of origin of the bulky temporal muscle is large and 

 rough. The zygomatic arch for the attachment of the masseter, 

 in spite of its incompleteness, is powerfully built and the man- 

 dible shows areas also indicative of large temporal and mas- 

 seter muscles. But turning to the Anteater we find quite a 

 different state of affairs. The mandible is reduced to a mere 

 splinter of bone showing the usual inferior dental and mental 

 foramina since the lower lip must receive its sensory nerves 

 though the teeth be absent, but in spite of a clearly defined 

 angle the condyle is rudimentary and the coronoid a mere ves- 

 tige. The last named feature suggests a poorly developed tem- 

 poral muscle and on reference to the skull it is seen that the 

 surface of origin of this muscle is restricted to a tiny postor- 

 bital area. The masseteric attachments are relatively less 

 greatly reduced but they are small and the pterygoid attach- 

 ments almost non-existent. There is a concavity of the palate 

 and weakness in the facial skeleton together with a rounding of 

 the occipital area all clearly indicating the effect of absence of 

 teeth. 



The lesson to be learned from the Edentates is then that the 

 absence of teeth results in weakness of the mandible and facial 

 skeleton, greatly reduced size of the masticatory muscles and 

 general smoothness of the skull. We note moreover that these 

 features may be distinguished independently of the type of 

 skull. 



Some years ago Professor Anthony in Paris compared the 

 skull of a dog from which six months before he had extracted 

 all the teeth with that of another animal of the same weight 

 from the same litter. The features which we have just ob- 



