50 ELEMENTARY ANATOMY. [LESS. 



The canal formed by the series of perforated transverse 

 processes may be replaced by one excavated inside the neural 

 arches, as in the cervical vertebrae of the Camels and Llamas. 



In some Cetaceans the external osseous boundary of the 

 perforated transverse process is wanting, so that there come 

 to be two elongated transverse processes on each side. 



The length of the cervical neural spines in man, though 

 much greater than in many animals, is yet quite insignificant 

 compared with the development they attain in certain Apes 

 (Gorilla, Orang, Perodicticus) and in the true Opossums. 

 Indeed, these animals show that the cervical spines may be 

 the longest ones of the whole vertebral column. In the true 

 Opossums and in some Armadillos their apices become 

 anchylosed together. 



The bifurcation of the neural spines is carried further 

 down the backbone (i.e. extends to more vertebrae) in man 

 than in any other mammal ; but this is not the maximum of 

 complication of the part, as in the Howling Monkeys 

 (Mycetes) we find a trifid spine. On the other hand, we 

 often meet with a bifurcation in the dorsal and lumbar regions 

 which is not present in the human skeleton. 



That faintly-marked prominence which exists in man in 

 front of the prezygapophysis is really a rudiment of a meta- 

 pophysis, as is plainly shown by the skeleton of the Spider 

 Monkey (A teles]. 



FlC. 64. AXIS AND FOUR FOLLOWING CERVICAL VERTEBRA OF A SPIDE.R 



MONKEY (A teles), 

 in, metapophysis. 



The smoothness of the anterior surface of the cervical 

 vertebral bodies in man is a great contrast to their condition 

 in some animals (as e.g. in Birds) ; for prominences (the hypa- 

 pophyses) on the post-cephalic vertebrae may (as in Crotalits) 



