On Motion in the lumbar division of the spine of birds, by George Oakley Fleming

                                <s>by ossific matter, so as to form one continuous bone. <\s>
Although, from what is stated, it will be seen that 
free lateral motion exists in the dorsal or lumbar 
portions of the spine of birds, it is evident that motion 
in an antero-posterior direction would be incompatible 
with flight; and there are no birds in which such 
motion exists, unless with the exception of the “nicht 
fliegenden Vogeln”, as Tiedman has called them, the 
ostrich, and the cassowary. In these birds, there is 
another point in which the skeleton differs from that 
of birds of flight; the pubic bones are united, as in 
the mammalia, affording stability and firmness to the 
pelvis, so necessary in running. 
There are beautiful contrivances to prevent motion 
in an antero-posterior, whilst they readily admit it 
in a lateral direction. The spinous processes of the 
vertebrae, which project at right angles from the bodies 
of the vertebrae, <s>and<\s> are situated exactly in a line with 
each other, having but a very small space between 
each. And in many cases, there are thin long flat bones, 
which are placed with their flat surfaces applied to 
each side of the spinous processes, preventing motion in 
a backward direction. These flat bones serve the pur-
pose of tendons, as the muscular fibres are attached to 
them