270 SKELETON. 



of his head and his erect position, keeps the head nearly in 

 equilibrium, it is comparatively feeble. 



4. Articulation of the Bony Bridges of the Vertebra. The in- 

 tervals between the vertebrae, at the posterior part of the spinal 

 canal, are filled up by the Yellow Ligaments, (Ligamenta Flavce,) 

 so called from their peculiar colour. These intervals exist be- 

 tween all the true vertebras, being bounded laterally by their 

 oblique processes,, and are very considerable in the loins, par- 

 ticularly that below the last vertebra; they are not so large in 

 the neck, and are still smaller in the back ; and their shape va- 

 ries considerably in the several portions of the spine. 



The yellow ligaments are two in number, forming a pair in 

 each of these intervals : the two approach, behind, at an angle, 

 in a line with the spinous processes, but are kept separated by 

 a small vertical fissure filled up with cellular substance. They 

 extend to the oblique processes laterally; are connected to the 

 anterior face of the bony bridge of the vertebra above; where- 

 as, they are inserted into the superior margin of that of the ver- 

 tebra below. From this arrangement, the yellow ligaments 

 may be best seen on the side of the spinal canal. The angle 

 which they form, behind, is continuous with the ligaments be- 

 tween the spinous processes. 



These yellow ligaments are smooth and shining on their an- 

 terior surfaces, but behind they are rough and unequal. Their 

 fibres are numerous and extremely compact, their strength is, 

 therefore, very great. Their elasticity is well marked and pe- 

 culiar to them, and assists greatly in erecting the spine when it 

 has been curved forwards. Bichat says that there is but little 

 cellular tissue between their fibres: that they are dissolved with 

 extreme difficulty in boiling water, and resist its action to such 

 a degree, that it is manifest they contain much less gelatine than 

 the greater number of analogous organs. 



The first pair of yellow ligaments is between the second and 

 third cervical vertebras, and the last between the last lumbar 

 and the sacrum ; there are, consequently, only twenty-three pairs 

 in all. 



Particular Articulations of the Spine. 



1. Articulation of Occiput with Atlas. The Anterior Ligament 

 s placed at the anterior part of the occipital foramen, and ex- 



