THE SKELETON 423 
notochord, and rapidly spread in all directions, but particularly 
towards the surface, leaving cartilaginous ends (Fig. 241). The 
notochord is gradually reduced and exhibits two constrictions 
Fic. 240. — The first cervical vertebre of a young 
embryo of Haliplana fuliginosa. (After Schauins- 
land.) 
s.n.b.1,2, First and second subnotochordal bars. 
R. 3, 4,5, 6, Ribs of the third, fourth, fifth, and sixth 
cervical vertebrie. 
and three enlargements within each centrum. The main en- 
largement occupies the center and the two smaller swellings the 
cartilaginous ends, the constriction occurring at the junction of 
the ossified areas and cartilaginous ends (Fig. 241). 
Fig. 241. — Section through the body of a cer- 
vical vertebra of a chick embryo of about 12 
days. (After Schwarck.) 
1, Endochondral ossification. 2, Articular 
cartilages. 3, Notochord. 4, Loosening of cells 
of the intervertebral dise, forming a synovial 
cavity. 5, Periosteum. 6, Ligamentum  sus- 
pensorium surrounding the notochord. 
