Tfw Diagnosis of the Diseases of Poultry 41 



The Normal Anatomy of the Domestic Fowl 



Before undertaking a discussion of post-mortem appear- 

 ance it is desirable to sketch in a brief way the most essen- 

 tial features of the normal skeletal and visceral anatomy 

 of the fowl. If one will study this chapter with some care, 

 and at the same time dissect a specimen, it will give him a 

 sufficiently good understanding of the normal relations of 

 the parts to enable him successfully to undertake for him- 

 self post-mortem examinations of his birds. 



The Skeleton 



The bones of birds (zoological class Aves) are in their 

 structure somewhat different from the bones of other ani- 

 mals. The most essential difference consists in the fact 

 that there are in the bones of birds, as a class, spaces which 

 are normally filled with air, forming a part of the general 

 air sac system connected with the lungs. The degree to 

 which the bones have the capability of being filled with air 

 varies considerably in the different orders of birds. In 

 the genus Gallus (the domestic fowl) this possibility is small 

 as compared with what obtains in flying birds, for example. 



The skeleton of the cock is shown in Fig. 6. Its main 

 divisions are: the skull (1); the neck (5); the trunk and 

 the limbs (wings and legs). 



Two parts are to be distinguished in the skull : first, 

 the brain case or cranium proper (1) and, second, the face, 

 including the beak (2, 3, and 4). As the skull bones grow 

 together early, one usually does not see in the skull of the 

 adult bird any division or sutures between the bones. 



The trunk skeleton includes the backbone or vertebral 

 column, the ribs, the breastbone, and the limb bones. 



The skeleton of the neck (5) is made up of 13 separate 



