402 DEVELOPMENT OF ORGANS IN MAMMALIA. [CHAP. 



Longitudinal Section through the Intervertebral Liga- 

 ment AND ADJACENT PARTS OF TwO VeRTEBR^ PEOM THE 



Thoracic Eegion of an advanced Embryo op a Sheep. 

 (From Kolliker.) 



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

 terius ; li. ligamentum intervertebrale ; k, k'. epiphysis of 

 vertebra ; w. and y/. anterior and posterior vertebrse ; c. in- 

 tervertebral dilatation of notocbord ; 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 sufficiently striking to need 

 a special description. 



