40 LECTURE II. 



dividual bones of the skeleton, with the occipital and parietal bones, 

 with the dorsal vertebrae, or the tibise ? 



In considering this and other questions previously discussed, you 

 will begin to appreciate the difficulties in defining or determining 

 what shall be considered a distinct and an individual bone in the 

 skeleton. 



If we apply to each species the anthropotomical definition of a 

 bone, as " any single osseous piece of which the skeleton of the ma- 

 ture animal is composed," we must qualify it by subordinate de- 

 finitions of the different natures of such separate pieces of the skeleton. 

 Hitherto bones have been primarily classified according to their 

 form, as long and cylindrical, broad and flat, thick and squab, 

 symmetrical, or unsymmetrical (xni. xi. pp. 9, 10.); or, according to 

 their position, into median* and lateral (xvi. p. xviii.), or into en do- 

 skeletal, exo-skeletal, and splanchno -skeletal bones (i. p. 113. 115.). 

 But, besides these, the above discussed deeper and more essential 

 differences of the bones require that they should be divided into 

 simple, as being developed from a single centre, and compound, as 

 developed from separate centres ; and the compound bones, in the 

 human subject, for example, may be subdivided into the teleologically 

 compound, as the ossa cylindrica, which are originally developed 

 from separate centres in relation to a spinal final purpose ; and the 

 homologically compotmd, as most of the ossa lata (occiput, scapula), 

 and many ossa mixta (vertebrae, sacrum), which are developed from 

 separate centres, representing permanently distinct simple bones in 

 other Vertebrata. 



The teleologically compound bones have their relations limited to 

 the particular exigencies of particular classes, but the homologically 

 compound bones have relations extending over the whole vertebrate 

 series. 



The great aim of the philosojihical osteologist is to determine, 

 by natui'al characters, the natural groups of bones of which a verte- 

 brate skeleton typically consists ; and, next, the relations of individual 

 simple bones to each other in those primary groups, and to define the 

 general, serial, and special homologies of each bone throughout the 

 vertebrate series. 



By general homology I mean the relation in which a bone stands to 

 the primary segment of the skeleton of which it is a part ; thus, when 

 the basi-occipital bone (basilar process of the os occipitis in anthropo- 



* These are mostly symmetrical ; but the youngest anthropotomist must have 

 met with instances of a curved vomer, and an unsymmetrical sternum ; and, on the 

 other hand, most of the phalanges among the ossa paria, sen lateralia, are sym- 

 metrical. 



