THE SKELETON. o7 



individuality in the ordinary mammalian and human skull. In many 

 Mammalia we find the pterygoid processes of anthropotomy per- 

 manently distinct bones ; even in Birds, where the progress of ossific 

 confluence is so general and rapid, the pterygoids and tympanies, 

 which are subordinate processes in Man, are always independent 

 bones. 



In many Mammalia the styloid, the auditory, the petrous, and the 

 mastoid processes remain distinct from the squamous or main part of 

 the temporal, throughout life ; and some of these claim the more to be 

 regarded as distinct bones, since they obviously belong to different 

 natural groups of bones in the skeleton ; as the styloid process, for 

 example, to the series of bones fbrming the hyoidean arch. 



The artificial character of that view of the os sacrum, in which this 

 obviously more or less confluent congeries of modified vertebrae is 

 counted as a single component bone of the skeleton, is sufficiently 

 obvious. The os innominatum is represented throughout life in most 

 reptiles by three distinct bones, answering to the iliac, ischial, and 

 pubic portions in anthropotomy. The sternum in most quadrupeds 

 consists of one more bone than the number of pairs of ribs which join 

 it ; thus it includes as many as thirteen distinct bones in the Bradypus 

 didactylus. 



The arbitrary character of the above cited definition of a bone, 

 and the essentially complex nature of many of the single bones and 

 independency of the processes of bone in anthropotomy, are taught 

 by anatomy, properly so called, which reveals the true natural groups 

 of bones, and the modifications of these which peculiarly characterise 

 the human subject. 



It will occur to those who have studied human osteogeny, that 

 the parts of the single bones of anthropotomy which have been 

 adduced as continuing permanently distinct in lower animals, are 

 originally distinct in the human foetus : the occipital bone, for 

 example, is ossified from four separate centres ; the pterygoid pro- 

 cesses have distinct centres of ossification ; the styloid, and tlie 

 mastoid processes, and the tympanic ring, are separate parts in the 

 foetus. The constituent vertebra) of the sacrum remain longer dis- 

 tinct ; and the ilium, ischium, and pubes are still later in anchy- 

 losing together, to form the ' nameless bone.' 



These and the like correspondencies between the points of ossifica- 

 tion of the human foetal skeleton, and the separate bones of the adult 

 skeletons of inferior animals, are pregnant with interest, and rank 

 among the most striking illustrations of unity of plan in the verte- 

 brate organisation. 



Cuvier, commenting on the arbitrary character of some of the 



