272 REPORT— 1846. 
birds, where the progress of ossifie confluence is so general and rapid, the 
pterygoids and tympanics, 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 ir 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 vertebra 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 fcetal 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 imaginé de compter autant d’os qu'il y a de centres d’os- 
sification distincts, et ayant essayé de suite cette maniére de faire, jai eu 
lieu d’apprécier la justesse de cette idée*.” Cuvier adopted and retained 
the same idea to the last. Commenting in the posthumous edition of the 
‘Lecons d’Anatomie Comparéet’ 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 Muséum, t. x. p. 344. 
+ Tom. i. 1835, p. 120. “ Mais ces distinctions sont arbitraires, et pour avoir le véritable 
nombre des os de chaque espéce, il faut remonter jusqu’aux premiers noyaux osseux tels 
qu’ils se montrent dans le foetus,” 
