B I R 



B I R 



TJBLE of the Number of the Vertelra in Birds, 



The eermcal ■vertelrdi are joined to each other by a mode 

 of articulation which admits of very free motion in two di. 

 reftions ; — laterally, and hackivards or forwards. This de. 

 pends \ipon the form of the a ticular furfaces of the bodies 

 of the vertebra, which confill of two porlionsof a cylinder 

 applied crofswavs with refpeiS to each other, and both a 

 little hollowed for their mutual accommodation. The cy- 

 linder on the inftrior part of the vertebrae, performs by its 

 revolution the motion to either fide ; and when that of the 

 fuperior part revolves, the neck is bent either backwards 

 or forwards. The cylinders at the top of the neck ad. 

 mit of motion forwards; but thofe of the middle and infe- 

 rior part of the cervical fp'ne are incapable of performing a 

 free motion forwards, as one contains a flight dcpreflion on 

 its anteror part, which receives the edge of the other. 

 The neck of birds, therefore, poflcffcs in the contracted 

 (late, or when at rell, fomewhat of the figure of an S, 

 which is accompanied with feveral advantages to thefe ani- 

 mals. They are enabled by it to throw the weight of the 

 neck and the head more over their centre of gravity, with, 

 out which fome fpccies would be unable to preferve tiieir 

 equdibrium ; and by combining the S like motion with 

 that to each fide, birds acquire a greater degree of flexi- 

 bility in the neck than is poffefled by other animals; 

 they can touch every point of their own body with the 

 bill, and thus fupply the want of the prehenfilc faculty 

 of the fuperior extremity or the tail, of which they are de- 

 prived by their peculiar mode of progrelfion. 



Tiie furfaces of the articular proceffcs lie nearly in the di- 

 reftion of the bodies of the vertcbrx, but in foir.e parti have 

 a degree of obliquity conformable to the S like fiiape of the 

 neck. 



The fpinous proceflcs are orilv to be obferved 'on the fu- 

 perior and inferior portions of the cervical fpine, where they 

 exift both on the anterior and polttrior parts c f the verte- 

 brx. In birds with long necks there is a folfa in each fide 

 of the poftcrior fpinous proceffes, for the attachment of 

 the cervical ligament, or Ugamcntiim nucha. This fubflance 

 is to be obferved perhaps in all birds, but is very remark-ble 

 in ihcjlort, fivan, caffonuiiry, and ojlr'ich. In the laft bird 

 it is nearly as llrong as it exilts in the larger quadrupeds : llie 

 fame kind of ligament is alfo interpoltd between the fpi- 

 nous proceffes of the dorfal vertcbrjc. 



The tranfverfe proceffcs of the vertebrse of the mi 'die of 

 the neckfpread forwards, and fend down a ilyloid procefs of 

 fome length. Thefe give attachment to niufdci. and fornj 

 in fome birds a fort of canal on the anterior part ot the neck, 

 which contains the two carotid arteries. The anteri -r Ify. 

 loid proceffes are little obfcrvable in the rapucirm-i and ftijp-r- 

 ine tribes, the piirrot. l^e- ; but are ulually very maiktJ in 

 the long-necked birds. 



The ilorfii vertebra of birds have fcarcely any motion, in 



order 



