140 



CHARACTERS OF VERTEBRATE ANIMALS 



hung by a bare patch of swollen skin, the cere. The large eyes 

 are provided not only with upper and lower eyelids, but also with 

 a translucent nictitating membrane, or third eyelid, which can be 

 rapidly twitched over the front of the eye by special muscles. 

 A narrow bare area of skin surrounds each eye, and in such breeds 

 as the Carrier, this area and the cere are highly developed into 

 peculiar fleshy outgrowths. Below and behind the eye is the 



CEREBELLUM^ 



OPTIC LOBE- 

 MEDULLA OBLONGATA- 



/fcEREBRAiX .OLFACTORY LOBE 



VHEHISPHERa(^_ /CERE 



'NOSTRIL 



URETER 

 LARGE INTESTINE 



ui I'niTk'^!,'^ 



Fig. 99. — General Structure of Pigeon 



small round auditory aperture, which is not provided with a pinna 

 as in most mammals. 



The long and exceedingly mobile neck is sharply marked off 

 from the stout boat-shaped trunk, which is terminated by a stumpy 

 tail, on the upper surface of which is a prominent papilla carrying 

 the aperture of the large oil-gland. On the under side of the 

 trunk, near its hinder end, is the opening of the cloaca, a small 

 chamber into which open the intestine, the kidney-ducts, and the 

 ducts of the reproductive organs. 



The body of a bird exhibits innumerable adaptations to an 

 aerial life, and this is seen very strikingly in the fore-limbs, which 

 are modified into wings, quite different, however, in structure 

 from those of a bat (see p. 81). The same sections are present 

 as in a mammal, i.e. upper arm, fore-arm, and hand, but there 

 are considerable differences in detail. In so far as folds of skin 



