ARTICULATIONS OF THE HEAD. 135 



another, mill tin- supi rsjn'iions ligament, becoming very tense, soon imposes 

 limits to this movement. 



i"..rt<-nKin is i tVn-tcd by an inverse mechanism, and is checked by the 

 tension of the common inferior ligament and the meeting of the spinoiis 

 processes. 



Lciti-nil iit<-l iiiation takes place when the spine bends to one side. This 

 movement is very easily executed in the cervical and coccygeal regions, but 

 is arrested by the ribs and the costiform processes in the dorso-lumbar 

 region. 



A circiimjlc.c movement is possible at the two extremities of the vertebral 

 column luck and tail; for they pass easily from extension to lateral 

 inclination, and from this to flexion, etc. 



Owing to the elasticity of the intervertebral fibro-cartilages, the spine 

 is endowed with a very limited amount of rotation, or rather of torsion. 



For the special study of the movements of each spinal region, reference 

 must be made to what has been already said (page 29) regarding the 

 mobility of this column. 



In the Ox the intervertebral discs arc much thicker than in the Horse. The common 

 inferior verti -l>ral ligament is very strong in the lumbar region. The superspinous 

 dorso-lnmbar ligament is composed of yellow elastic tissue. The cervical ligament 

 is much more drvi I"|MI! than in Solipeds, in consequence of the greater weight of 

 tlie head ; and it presents a conformation altogether special, which M. Lecoq has made 

 Uini\Mi in the following terms: "On leaving the withers, the superspinous ligament 

 - to cover the head of the spinous processes, and extends from each side in a wide 

 and strong band, taking points of attachment on the sides of the processes, and becoming 

 ted. on leaving that of the first dorsal vertebra, into two parts a superior and 

 inferior. The first reaches the cervical tuberosity in the form of a thick cord united to 

 the r.ird of the i'i>i><>.-ite ; the other thins off into a luid which is attached to the posterior 

 half of the spinnus process of the axis and to that of the third and fourth vertebra). A 

 prediction of tlie same nature, an auxiliary to the principal portion, leaves the anterior 

 ixinler of the >]iinons [inn-ess of the first dorsal vertebra, and is attached to that of the 

 fourth, tifili, .-i\th, and seventh vertebra). The superior border of this auxiliary liga- 

 nieiitoiH produetion is concealed 1.. twe, u the two lamina of the principal ligament." 1 



Tlie 1'iij, n-murkaUe for the shortness of its neck and the limited movements of this 

 . d". - not r-how any e. rvieul ligament, properly so called. It is replaced by a 

 Mi|H rlieial fibrous raphe extending from the occipital bone to the spinous process of the 

 tir.-t d.-r.-.il v. rtebra. 



The <',,i )i:i.-, no cervical ligament, and shows, instead, a raphe like the Pig. In 

 the l>'i the ligament is reduced to a simple e>rd. continued from the dorso-luml ar 

 IL'imii lit. and which go.- no Inrther than Ix-hind th-- spinous process of the a\is. In 

 the I'ul the interspiii'.iis ligaments are replaced liy small muscular fasciculi ;. with tho 

 I><H/ this Mili.-titution imly takes place in the cervical region. The lamina- of the lir.-t 

 coccygeal vertebrae jx>ss, ss the principal characters which distinguMi |xrlect vcrtebrw 

 .re uniteil l.y \e>tiges of tlio articular bunds which exist in the other regions of 



ARTICLE II. ABTICULATIONS OF THE HEAD. 



Wo will first study the two extrinsic articulations which are the centra 

 of tin- movements of the head on the spine the atlo-^unid and t>cciptht-atl'nl 

 irt'n-idations. Afterwards, we will pass to the examination of the joints which 

 unite the different bones of the head. 



1. Allo-axoid Articulation. 



(Ti.jnt r<tti'<,n. -- It siifliees to remove the Hoft parts from around the artii-nlatimi to 

 the inti raiinular, the iiiter.-piin'iis, and tin i uteri- >r <lont.>id ligament. 'J'u . xaiuine 



Joiiin.d d' M.<1" in, \ -is. p. Vll. 



