272 report — 1846. 



birds, where the progress of ossific confluence is so general and rapid, the 

 pterygoids and tympanies, which are subordinate processes of other bones in 

 man, are always independent bones. 



In many mammals, the styloid, the auditory, the petrous, and the mastoid 

 processes remain distinct from the squamous plate of the temporal, through- 

 out 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 forming the hyoi- 

 dean arch. 



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

 or less confluent congeries of modified neural arches 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, answer- 

 ing 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 definition of a bone, as ' any single piece of 

 osseous matter entering into the composition of the adult skeleton,' the com- 

 plex nature of many of such single bones, and the essential individuality of 

 some of the processes of bone in anthropotomy, are taught by anatomy, pro- 

 perly so called, which reveals the true natural groups of bones, and the modi- 

 fications 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 processes have distinct centres of ossification ; the styloid, and 

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

 The constituent vertebrae of the sacrum remain longer distinct ; and the ilium, 

 ischium, and pubes are still later in anchylosing together, to form the ' name- 

 less bone.' 



These and the like correspondences between the points of ossification 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 stri- 

 king illustrations of unity of plan in the vertebrate organization. 



The multiplication of centres from which the ossification of an ultimately 

 single bone often proceeds has especially attracted the attention of the philo- 

 sophical anatomists of the present century with reference to the right or 

 natural determination of the number of the constituent parts of the verte- 

 brate skeleton. Geoffroy St. Hilaire, in his memoir on the skull of birds, in 

 1807, says, " Ayant imagine de compter autant d'os qu'il y a de centres d'os- 

 sification distincts, et ayant essaye de suite cette maniere de faire, j'ai eu 

 lieu d'apprecier la justesse de cette idee*." Cuvier adopted and retained 

 the same idea to the last. Commenting in the posthumous edition of the 

 1 Lecons d'Anatomie Compareef ' on the character of some of the defini- 

 tions of single bones in anthropotomy, he, also, concludes that, in order to 

 ascertain the true number of bones in each species, we must descend to the 

 primitive osseous centres as they are manifested in the foetus. But according 

 to this rule we should count the humerus as three bones and the femur as four 



* Annales du Museum, t. x. p. 344. 



•f Tom. i. 1835, p. 120. " Mais ces distinctions sont arbitraires, et pour avoir le veritable 

 nombre des os de chaque espece, il faut remonter jusqu'aux premiers noyaux osseux tels 

 qu'ils se montrent dans le foetus." 



