CERVtCAL VERTEBRAE 2 1 



vertebra there may lie a ventral median process, arising of course 

 from the centrum, termed the hypapophysis. 



From the sides of the neural arch, or from the centrum 

 itself, there is commonly a longer or shorter process on each 

 side, known as the tra,ns\'erse process. This is sometimes 

 formed of two distinct processes, one above the other ; in 

 such cases the upper part is called a diapophysis, the lower 

 a parapophysis. 



The neural arch may also bear other lateral processes, of 

 which one directed forwards is the metapophysis, the other 

 directed backwards the anapophysis. 



The series of bones which constitute the vertebral column 

 can be divided into regions. It is possible to recognise cervical, 

 dorsal, lumbar, sacral, and caudal vertebrae. In the case of 

 animals with only rudimentary hind-limbs, such as the ^^'hales, 

 there is no recognisable sacral region. The neck or cervical 

 vertebrae are nearly always seven in number. The well-known 

 exceptions are the Manatee, where there are six, and certain 

 Sloths, where there are six, eight, or nine. These rare exceptions 

 only accentuate the very remarkable constancy in number, which 

 is very ilistinctive of the mammals as compared with lower 

 Yertebrata. There are of course abnormalities, the last cervical, 

 and sometimes the last two, assuming the characters of the 

 ensuing dorsals, by developing a more or less complete rib. 

 There are also recorded examples of Briidi/jii/^i, in which the 

 number of cer^icals is increased to ten. Tlie characteristics, 

 then, of the cervical vertebrae are, in the first place, that they 

 do not normally bear free ribs, and that there is a break as a rule 

 between the last cervical and the first dorsal on this account. In 

 liirds, for example, the cer\'icals, diifering in number in different 

 families and genera, gradi^ally approach the dorsal.'^ by the 

 gradually lengthening ribs. The transverse processes of the 

 vertebrae are commonly perforated by a canal for the vertebral 

 artery, and are bifid at their extremities. In some Ungulates 

 these vertebrae, more(j'S'er, approximate to the vertebrae of lower 

 Yertebrata in the fact that there are l)all and socket joints 

 between the centra, instead of only the fibrous discs of the 

 remaining vertebrae. 



The first two vertebrae of the series are always very 

 different from those which follow. The first is termed the 



