1306 



SURFACE ANATOMY AND SURFACE MARKINGS 



thoracic; of these the latter is the more prominent. The root of the spine of the 

 scapula is on a level with the tip of the spinous process of the third thoracic vertebra, 

 and the inferior angle with that of the seventh. The highest point of the iliac 

 crest is on a level with the spinous 





on 



process of the fourth lumbar, and the 

 posterior superior iliac spine with that 

 of the second sacral. 



The transverse process of the atlas 

 is about 1 cm. below and in front of 

 the apex of the mastoid process. The 

 transverse process of the sixth cervical 

 vertebra is opposite the cricoid cartil- 

 age; below it is the transverse pro- 

 cess of the seventh and occasionally 

 a cervical rib. 



Fio. 1213. Sagittal section of vertebral canal to 

 show the lower end of the medulla spinalis and the 

 filum terminale. (Testut.) Li, Lv. First and fifth 

 lumbar vertebrae. Sii. Second sacral vertebra. 1. 

 Dura mater. 2. Lower part of subarachnoid cavity. 

 3. Lower extremity of medulla spinalis. 4. Filum ter- 

 minale internum, and 5, Filum terminale externum. 

 6. Attachment of filum terminale to first segment of 

 coccyx! 



z "^Cervical! 



> 3 r . d Cervical 



th Cervical 



? ^Cervical 



Coccygeal 



FIG. 1214. Scheme showing the relations of the 

 regions of attachment of the spinal nerves to the verte- 

 bral spinous processes. (After Reid.) 



Medulla Spinalis. The position of the lower end of the medulla spinalis varies 

 slightly with the movements of the vertebral column, but, in the adult, in the 

 upright posture it is usually at the level of the spinous process of the second lumbar 

 vertebra (Fig. 1212) ; at birth it lies at the level of the fourth lumbar. 



The subdural and subarachnoid cavities end below opposite the spinous process 

 of the third sacral vertebra (Fig. 1213). 



