28 THE STRUCTURE AND LIFE OF BIRDS ch. ii 



Its remarkable form of pelvis is of great advantage 

 to the bird. It has helped in the stiffening of the 

 backbone ; it gives room for the attachment of the 

 large muscles necessary now the quadruped has be- 

 come a biped ; its backward extension is useful for 

 the attachment of the muscles that move the tail. The 

 lizard's pelvis, hanging downward from the backbone, 

 looks like a different organ. The bones, however, 

 are the same. The Ilium attaches to the vertebral 

 column, and the other two can be made out by their 

 position relatively to it and to each other ; the Ischium 

 forming the hinder part of the socket in which the 

 thigh-bone moves, the Pubis the anterior part. 



Some Books on the Subject. 



Marshall and Hurst's Practical Zoology. 



Parker's Zootomy. 



Huxley's Vertebrate Anatomy. 



Gegenbaur's Comparative Anatomy. 



Alix's Essai sur Vappareil locomoteur des Oiseaitx. 



