402 DEVELOPMENT OF ORGANS IN MAMMALIA. [CHAP. 



Longitudinal Section through the Intervertebral Liga- 

 ment AND ADJACENT PaRTS OP TwO VERTEBRAE FROM THE 



Thoracic Region of an advanced Embryo of a Sheep. 

 (From KoUiker.) 



la. ligamentum longitudinale anterius ; Ip. ligamentum long, pos- 

 terius ; U. ligamentum intervertebrale ; /, l'. epiphysis of 

 vertebra ; w. and w'. anterior and posterior vertebrae ; c. in- 

 tervertebral dilatation of notochord ; c' and c". vertebral di- 

 latation of notochord. 



The early changes in the development of the visceral 

 arches and clefts have already been described, but the 

 later changes undergone by the skeletal elements of the 

 first two visceral arches are sufificiently striking to need 

 a special description. 



