BIRDS. 50.' 5 



of the neck, we find scarcely a trace of these 

 processes in the cervical vertebrae of birds. But 

 another, and a still more important consideration 

 was to be attended to in the construction of 

 this part of the spine. It must be recollected 

 that the spinal marrow passes down along the 

 canal formed by the arches of the vertebrae, 

 and that any pressure applied to its tender 

 substance would instantly paralyze the whole 

 body, and speedily put an end to life. Some 

 extraordinary provision was therefore required 

 to be made, in order to guard against the 

 possibility of this accident occurring during the 

 many violent contortions into which the column 

 is liable to be thrown. This is accomplished in 

 the simplest and most effectual manner by en- 

 larging the diameter of the canal at the upper 

 and lower part of each vertebra, while at the 

 225 ^ middle it remains of the 



usual size, so that the 

 shape of the cavity, as 

 is well seen in Fig. 225, 

 which shows a vertical 

 section of one of the 

 cervical vertebrae of the 

 ostrich, resembles that 

 of an hour glass.* Thus 

 a wide space is left at 

 the junction of each successive vertebra, allowing 



* For the specimen from which this engraving was made, I 

 am indebted to the kindness of Mr. Owen. 



