m.MI'AKATIVi: ANATOMY. 



processes may unite with the corresponding ribs (Fig. 35). In 

 the thoracic region, more or fewer of the vertebra- usually become 

 immovably united together. 



06 







Ft . / 



/; rt vPsi 



IMC. 35. THIKII CKKVK \i, \"Ki:Ti:ni:.\ OF "VYoonrKcicKi: (/'<V</.s- ///////->). (Viewed 



anteriorly.) 



>', articular surface of centrum ; Ob, upper arch ; TV/., articular process ; Pi, I'/, tin- 

 two bars of tlic transverse process, shown on one side :incliylo<eil \\iih the < -i-r\ 'ical 

 rib (7,'j ; Ft, transverse (vortebrarterial) foramen ; Put, ha-mal spine. 



Mammalia. No direct connection exists between the 

 vertebra- of Reptiles and Birds and those of Mammals. The 

 notochord persists longer intervertebrally than vertebrally, lint it 

 disappears entirely by the time the adult condition is readn-d. A 

 jelly-like pulpy mass, the nucleus pulposus, persists, however, 

 throughout life in the centra of the EuSro-cartilaginous menisci 

 which are developed between the vertebrae. Articulations between 

 the centra are never formed, but, as in Amphibians, Reptiles, a ml 

 Birds, well-developed articular processes are present, arising from 

 the neural arches. 1 The cervical region is usually the rn<e-t 

 moveable, and the centra may be so much hollowed out in tin- 

 region as to give them an opisthoccelous character (e.g. Ungulata). 

 In some cases, on the other hand, the cervical vertebrae may become 

 firmly fused together (Cetacea). The centra are provided with epi- 

 physgs^ except in all but those of the caudal region of Monotremes 

 and in Sirenia C?). 



The atlas and axis essentially resemble those of Birds, though 

 the differentiation of the vertebral column into regions, characterised 

 by difference of form, is much more sharply marked than in any 

 other Vertebrates. 



In long-necked Un;_ r ulates (llnrsr, faim-l, Ox) the neural spines of Ilic 

 .interim- tli<.racie vrrlclinr ;in- ^really (leveliqH-d, ami cMi-iv^h.ncliiig with this, 

 a strmii; cervical ligament (ligamentOBl inu-ha' is particularly well drM'lnpnl 

 to -ii|i]inrt the weight, of tin- head. This is also t rm: of ant ler-lieari IIL.' aniinaU 

 and df tin- (Jorillu. There are as a rule 7 cervical vei-ielu-.c ; Uradypus, lm\v- 

 e\ cr. ]>"--e-:sc'9 8 9, and Tamandiia bivittata 8, while in Manalu- and ( 'Imhrjnis 

 there are .,n|y 6. 



The tran-vei-e proceaeee "f the cervical verlel. r;c usually unite with the 

 rudimentary ril>-\ aa in I'.irds. 



1 In certain K.leniaia c /. .Mynii.-co]iha.i,'iii e\tra articular processes are \ 



the ordinary /y^,ipo|iliy-e> on the- jiostcrior thoracic and lumhar 



