278 STRUCTURE AND CLASSIFICATION OF BIRDS 



considered. But the first two or three rings of the bronchus 

 are complete rings with no membrane internally. From the 

 fourth onwards the rings are semi-rings. Upon the sixth 

 are inserted the syringeal muscles. Coua is somewhat inter- 

 mediate. The first seven bronchial semi-rings have their 

 inner extremities separated by a narrow area of membrane. 

 To the seventh are attached the intrinsic muscles of the 

 syrinx. From this point commences the tympaniform mem- 



FIG. 138. SYRINX OF Centropus atcralbus (AFTER BEDDABD). 

 A. FRONT VIEW. B. BACK VIEW. 



brane. The accompanying woodcuts will serve to illustrate 

 the varying form of the syrinx among the Cuculi. 



As with some other large groups of birds, such as the 

 pigeons and parrots, the gall bladder is present in some 

 cuckoos and absent in others. The gall bladder exists in 

 the genera Saurothera, Coccyziis, Guira, Pyrrhocentor, 

 Scythrops, and Cuculus ; it is absent in Cro'tophaga and in 

 some species of Centropus. Coua has a gall bladder ; Eudtj- 

 iKtinix appears not to have one. 



In Guira the right lobe of the liver is five or six times as 

 large as the left. 



The main artery of the leg is the femoral in Piaya, Cen- 

 tropus, the sciatic in Diploptera, Saurothera, Cocci/:://*, 

 Pyrrhocentor. 



