110 



Basic Structure of Vertebrates 



o&pc. 



rclc a)r. st. 



Fig. 108. (Left) Dorsocaudal aspect of atlas. (027) Anterior articular process; 

 (fr) aperture of the transverse foramen which enters the atlas at (»/); (nc) neural 

 canal; (sp) spinous process; (tr) transverse process; (zg) posterior articular process. 



(Right) Lateral aspect of the epistropheus (axis), (ar. st.) Anterior articular 

 process; (nl, sp.) neural spine or spinous process; (od. pr.) odontoid process; 

 (p. zg.) posterior articular process; (trs. pr.) transverse process; (vrt. c.) transverse 

 foramen. (Courtesy, Stromsten: "Davison's Mammalian Anatomy," Philadelphia, 

 The Blakiston Company.) 



EPIDERMIS 



DERMATOME 



MYOTOME 



SCLEROTOME 



Fig. 109. A diagram showing the relations of myotomes and sclerotomes as 

 seen in a horizontal section of a vertebrate embryo. (A) Anterior; (P) posterior. 

 The upper half of the figure shows the relations in an earlier stage of development, 

 while the lower half represents a later stage. The posterior half (finely dotted) of 

 each sclerotome unites with the anterior half (coarsely dotted) of the following 

 sclerotome to form a centrum. Thus the centra alternate in position with the myo- 

 tomes and each myotome becomes attached to two vertebrae. (Courtesy, Neal 

 and Rand: "Chordate Anatomy," Philadelphia, The Blakiston Company.) 



