Nervous system and Sense organ of Pigeon
The brain is divisible into the fore-, mid- and hind brains. The cerebral hemispheres are distinct. They are round and large in size. Theolfactory lobes are very small and they do not contain cavities. The diencephalon is hidden from the view by the forward prolongation of thecerebellum . The diencephalon has the pineal body dorsally and infundibulum and pituitary body ventrally. The optic lobes are lateral inposition owing to the large size of the cerebral hemispheres and cerebellum. The medulla oblongata instead of being continued backwards as in other tetrapods, descends almost vertically from the cerebellum
In pigeon the olfactory sense is poor. There is no external ear. The tympanum is slightly sunken from the surface of the skin.
The eyes are large. During flight the eyes and their shape are pro-tected by unique sclerotic plates of the outer eye layer. The nictitatingmembrane slides over the eyeball and presumably protects the cornea by closing it, during flight. Inside the eye, a vascular pigmented process projects into the vitreous body. It is know as the pecten. It arises from the point of entry of the optic nerve into the eye ball. Its function is not definitely known, but possibly it may help in long distance vision.
Sub phylum - Vertebrata
Class - Av e s
Order - Columbiformes
Type - Columba livia
Birds are easily recongnised group of vertebrates. In birds every part of the body is modified to suit their aerial mode of life. Birds possess feathers, beak and feet modified in relation to their aerial life.
The Pigeons are flying birds(carinate). They are known both as wild and domesticated forms. The Pigeons are seen both in tropical and temperate zones. About 10 species of Pigeons are found in India. The pigeons fly in flocks and roost together. The domestic pigeons have many varieties, namely panter, fantail and tumblers. They differ in size, colouration and feather ar-rangement. All of them are, however, descendants of the rock pigeon-columba livia.