PREFACE, xxv 



and rib. At a period long subsequent to the deposition of the 

 first centre of bone, a second appears at the sternal end of the 

 human clavicle, and two are added to complete the head and 

 tubercle of the lib, the shaft of which had been ossified by growth 

 from a single centre. 



Recognition of the archetype skeleton elucidates the empirical 

 facts of embryology, and teaches us to distinguish between the 

 points of ossification of a bone in a higher vertebrate which sig- 

 nify or answer to bones that retain their distinctness in lower 

 vertebrates, and the points of ossification which merely help out 

 the growth or have their final purpose in the exigencies of the 

 vouno- animal. A lamb or foal, e.o\, can stand on its fore legs 



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shortly after it is born, and soon begins to run and bound. The 



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shock to the limbs themselves is broken at this tender a;e by the 



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cushions of cartilage at the ends of the shafts, and which continue 

 for some time to be interposed between the ' epiphyses' and * dia- 

 physis.' The jar that might affect the large and pulpy brain 01 

 the immature man is similarly diffused and intercepted by the 

 ' epiphysial ' extremities of the vertebral centrums. 



Such final purpose in the several centres of ossification of the 

 vertebral bodies and the long bones of the limbs of mammals does 

 not apply to those of reptiles ; and no epiphyses with interposed 

 cartilage attend the growth of the limb-bones of saurians and 

 tortoises. But, when the reptile moves by leaps, ossification of 

 the long limb-bones by distinct centres again prevails; the ex- 

 tremities of the humeri and femora are ' epiphyses ' in the frog. 



Embryology affords no criterion between the ossific centres that 

 have a ( homological ' and those that have a ' ideological ' signifi- 

 cation. A knowledge of the archetype skeleton is requisite to 

 teach how many and which of the separate centres that appear 

 and coalesce in the human, mammalian, or avian skeleton, re- 

 present and are to be reckoned as distinct bones, or elements of 

 the archetype vertebra. For the want of this guide great and 

 estimable anatomists have gone astray. Thus CUVIER, comment - 



- on the arbitrary enumeration of the single bones in the human 



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