34 



THE AXIAL SKELETON 



Protovertebral (intercostal) artery 

 Arteria protovertebralis (intercostalis) 



Aorta - 





First vertebra 

 Vertebra I. 



Second vertebra 



Vertebra II. 



Third vertebra 

 Vertebra III. 



Fourth vertebra 

 Vertebra IV. 



First protovertebra 



Protovertebra i. 



Second protovertebra 



Protovertebra 2. 



Third protovertebra 



Protovertebra 3. 



4 Fourth protovertebra 

 Protovertebra 4. 



Fifth protovertebra 



Protovertebra 5. 



Intervertebral ganglion 



Ganglion intervertebrale 



FIG. 66. DIAGRAM SHOWING THE RELATIONS OF THE PROTO- 

 VERTEBR.E TO THE VERTEBRAE. (FROM VON EBNER.) 



Intervertebral disc 



Ligamentum interver- 

 tebrale 



Primitive cartilages 

 of the vertebral 

 bodies 



Notochord 



Chorda dorsalis 



FIG. 67. PRIMITIVE CARTILAGES OF 

 THE VERTEBRAL BODIES. 



From a sagittal section through the verte- 

 bral column of a human fcetus in the tenth 

 week. (Length of fcetus, 2j inches.) 



Centre of ossification of 

 the body of the ver- 

 tebra 



Vascular canal of the 

 cartilage 



Centre of ossifica- 

 tion of the arch of 

 the vertebra 



Primitive cartilage 

 of the second 

 lumbar vertebra 



Intervertebral disc - 



Ligamentum 



intervertebrale 



Centre of ossification 

 of the body of the 

 vertebra 



'/i 



^Primitive cartilage of 

 the arch of the first 

 lumbar vertebra 



FIG. 69. THE THREE CENTRES OF OSSIFICATION 

 OF A VERTEBRA. 



Horizontal section through the second and a portion of the 

 first lumbar vertebras of a human fetus in the beginning 

 of the fifth month (months of four weeks each). (Length 

 of fcetus, s inches.) 



Notochord 



Chorda dorsalis 



FIG. 68. CENTRES OF OSSIFICATION 

 OF THE BODIES OF THE VERTEBRA. 



From a sagittal section through the vertebral 

 column of a human fcetus in the fourth 

 month (months of four weeks each). 

 (Length of fetus, 4! inches.) 



Development of the Vertebrae. 



