OF THE HEAD. 155 



direction of the opening, with another line passing from the 

 posterior edge of the foramen to the inferior margin of the 

 orbit. This angle is of 3° in man, and of 37° in the orang- 

 utang ; 47° in the lemur. It is still greater in the dog ; and 

 in the horse it is of 90° or a right angle, the plane of the 

 opening being completely vertical. 



The distance of the foramen magnum from the front of 

 the jaws and the posterior surface of the occiput may be in 

 man respectively, as 3-5ths and 2-5ths, or even more nearly 

 equal : the former is twice as great as the latter in the orang- 

 utang ; while, in almost all other mammalia, the opening 

 is at the very posterior aspect of tlie skull. 



The teeth of man are distinguished by being all of one 

 length, and by the circumstance of their being arranged in an 

 uniform unbroken series. The cuspidati are a little longer 

 than the others at first ; but their sharp points are soon worn 

 down to a level with the rest. In all animals the teeth of 

 different classes differ in size and length, often very consi- 

 derably ; and they are separated by more or less wide inter- 

 vals : this is particularly the case with the teeth called canine, 

 or cuspidati, which are long, prominent, and distinct from 

 the neighbouring teeth: their not projecting beyond the rest, 

 nor being separated from them by any interval, is, therefore, 

 a very characteristic circumstance in the human structure. 

 Even in the simiae, whose masticatory apparatus most nearly 

 resembles that of man, the cuspidati are longer, often very 

 considerably longer than the other teeth ; and there are in- 

 tervals in the series of each jaw to receive the cuspidati of 

 the other. 



The inferior incisors are perpendicular ; the teeth, indeed, 

 and the front of the jaw are placed in the same vertical line. 

 In animals, these teeth slant backwards, and the jaw slopes 

 backwards directly from the alveoli ; so that the full pro- 

 minent chin, so remarkable a feature in the face of our 

 species, is found in no animal, not even in the orang-utang: 

 it appears as if the part were cut off. 



The obtuse tubercles of the grinders are again very pecu- 

 liar and characteristic ; they are worthy of particular remark. 



