28 THE STRUCTURE AND LIFE OF BIRDS cH. 
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 Practzcal Zoology. 
Parker’s Zootomy. 
Huxley’s Vertebrate Anatomy. 
Gegenbaut’s Comparative Anatomy. 
Alix’s E'ssad sur Papparetl locomoteur des Oiscaux. 
