There are many _functional centers_ located in the medulla oblongata. Destruction of this part of the system results in instant death of the bird. In addition to furnishing a path for fibers carrying impulses from the body to the cerebrum, it furnishes a large number of centers for such functions as respiration, swallowing, secretion, temperature, and vasomotor and cardiac activity. The _function of the cerebellum_ is principally that of coördination. It brings about harmony and rhythm in muscular movements. If the cerebellum be removed, the bird can no longer walk. It has lost, with this removal, all power to coördinate. The _cerebrum_ of the bird has no convolutions, and the gray, or ganglionic, portion is thin, indicating low power of intelligence. There are certain areas presiding over other functions, as motor areas, sensory areas, and so on. A careful study of the brain of the fowl shows us that the centers presiding over sight and smell are well developed. The olfactory bulbs are the centers of the sense of smell. The optic thalamus is the center of the sense of sight. The sympathetic nerve system transmits impulses to the involuntary muscular structure of all organs, including those of the intestinal tract, the blood-vessels, and perhaps also the glands. ESTHESIOLOGY THE SENSE ORGANS The five special senses are seeing, smelling, tasting, hearing, and feeling. THE ORGAN OF SIGHT The sense of sight in the bird is well developed. The eye (Fig. 26, _D_, _E_ and _F_), the organ of sight, is relatively large, round laterally, and rather flattened antero-posteriorly. It is located at the side of the head. The eyeball is only slightly movable. The septum interorbital separates the two eyeballs laterally. As in mammals, the eyeball has three coats, which are from inside to outside, the retina, the choroid, and the sclera. The =sclerotic coat= is completed anteriorly by the cornea with which it forms a union called the _corneo-scleral juncture_. Around the cornea the sclerotic coat contains a ring of osseous scales varying in number from twelve to twenty. The sclera may become ossified posteriorly, forming an osseous sheath around the optic nerve. The _pecten_ is a vascular comb-like membrane stretching from the nervous opticus to the crystalline lens. The choroid coat is always black. The pupil in the hen is also black and round. The iris contains striated muscular fibers. The _membrana nictitans_, located at the inner angle is well developed. It is moved by two muscles (Fig. 26, No. _B_, 7, 8, 10). The lacrimal gland and the gland of Harder are present. There is no meibomian gland. The _tears_ are secreted by the lacrimal gland and are drained away from the fore part of the eyeball by two small canals which extend into a lacrimal sac. From this sac there extends a tube into the nasal cavity called the lacrimal duct.