58 ELEMENTARY ANATOMY. [LESS. 



others, and sometimes unite into a strong crest even in Pri- 

 mates, but especially in the Rhinoceros, some Ruminants, and 

 Insectivora, e.g. Sorex and Myogale. 



The lower end of the sacrum in man is devoid of processes, 

 but in most forms there is a pair of strongly marked ones, 

 which are most probably tubercular processes with annexed 

 connate or developed ribs. 



Metapophyses and anapophyses are hardly to be detected 

 on the sacrum of man ; but they are distinctly visible in many 

 Mammals, even Monkeys. 



The occasional open condition of the neural canal in man 

 is very exceptional, being repeated only in the highest Apes. 



That the sacrum has a flat articular surface at one end 

 for the last lumbar vertebra, and at the other for the coccyx, is 

 the normal condition, but the vertebras composing it may, as 

 in Batrachians (e.g. Menopoitia and Cryptobranchus\ be con- 

 vex in front and concave behind. It may, however, present a 

 condition such that its two component vertebrae have the 

 conjoined surfaces of their centra flat, and the other surfaces 

 respectively concave, as in Crocodiles. 



30. No better example of the inadequacy of the exclusive 

 study of man for a full comprehension of his frame can pro- 

 bably be given than the human os coccygis. 



The anthropotomist, though he would readily perceive that it 

 was the rudimentary representative of a tail, would yet never 

 suspect to what diverse and curious structures it corresponds. 



Indeed, the COCCYGEAL REGION of the vertebral column, 

 instead of only varying as to the size and number of its parts, 

 is the subject of very peculiar modifications of structure, and 

 of unexpected modes of ossification and development. 



It may act as an extra hand ; it may be the main or exclu- 

 sive locomotive organ ; it may, together with the neck, contain 

 the only free vertebrae of the body ; or it may be still more 

 reduced and rudimentary than in man. 



It may in part consist of a solid bone formed by the fusion 

 of primitively separate vertebrae, or it may be distinguished 

 from the rest of the vertebral column as the only portion 

 never made up of separate vertebrae at any time of life. 



The three, four, or five coccygeal vertebras of man may be 

 represented by as many as forty-six in his own class namely, 

 in the long-tailed Pangolin or Manis ; and in his own order 

 it may reach the number thirty-three, as in the pre-eminently 

 arboreal Spider Monkeys, which have the tail prehensile, 

 serving as an additional hand. It may, on the contrary, in 



