OSSEOUS SYSTEM OF AVES. 59 



§ 127. Cervical Vertebra. — As the prehensile functions of the 

 hand are transferred to the beak, so those of the arm are per- 

 formed by the neck of the bird ; this portion of the spine is 

 therefore composed of numerous, elongated, and freely moveable 

 vertebrae, and is never so short or so rigid but that it can be 

 made to apply the beak to the coccygeal oil-gland, and to every 

 part of the body for the purpose of oiling and cleansing the 

 plumage. In birds that seek their food in water it is in general 

 remarkably elongated, whether they support themselves on the 

 surface by means of short and strong natatory feet, as in the 

 Swan, or wade into rivers and marshes on elevated stilts, as in 

 the Flamingo, fig. 14. 



The articular surfaces of the bodies of the cervical vertebrae, 

 like those of the dorsal series, are concave in one direction and 

 convex in the other, so as to lock into each other, and in such a 

 manner that the superior vertebras move more freely forward, the 

 middle ones backward, while the inferior ones again bend forward ; 

 producing the ordinary sigmoid curve observable in the neck of 

 the bird. 



This mechanism is most readily seen in the long-necked waders 

 which live on fish and seize their prey by darting the bill A\dth 

 sudden velocity into the water. In the common Heron, for 

 example (^Ardea cinerea), the head can be bent forward on the 

 atlas or first vertebra, the first upon the second in the same direc- 

 tion, and so on to the sixth, between which and the fifth the for- 

 ward ' inflection is the greatest; while in the opposite direction 

 these vertebras can only be brought into a straight line. From 

 the sixth cervical vertebra to the thirteenth the neck can only be 

 bent backward ; while in the opposite direction it is also arrested 

 at a straight line: from the fourteenth to the eighteenth the 

 articular surfaces again allow of the forward inflection, but also 

 limit the opposite motion to the straight line. 



An inter-articular cartilage is inclosed between reduplications 

 of the synovial membrane in most of the joints between the 

 bodies of the cervicals, as in the joint of »the lower jaw in mam- 

 malia. The zygapophysial articulations are simply synovial. The 

 par- and di- apophyses are at the fore part of the vertebras, and, 

 usually at the third cer\ical, coalesce with a styliform pleurapo- 

 physis projecting backward. The vertebrarterial canal, thus 

 formed, is large, and gives passage to both the vertebral artery 

 and the sympathetic nerve. 



The inferior processes from the cervical centrums are of two 

 kinds ; one single, developed from the mid-line, usually toward 



