I 3 8 



VETERINARY PHYSIOLOGY 



visual sensations, and hence this part of the brain is called the 

 visual centre. Usually the visual centre is stimulated by 



Occ. L. 



FIG. 67. The Connections of the Retinae with the Central Nervous System 

 in man and apes. , retinae ; Ch. , chiasma leading to optic tract ; 

 Op.Th., optic thalamus ; A.C.Q., anterior corpora quadrigemina ; Oc.M., 

 oculo-motor mechanism (fig. 66) ; Occ.L., occipital lobe of the cerebrum ; 

 Teg., tegmentum. 



changes in the chain of neurons passing from the retina and 

 set in action by retinal changes ; but direct stimulation of 

 the occipital lobe may induce visual sensations. 



(c) FOR VIBRATION OF AIR 



Sense of Hearing 

 1. General Considerations 



While through the tactile mechanism differences of pressure 

 act as stimuli, through the ear certain vibratory changes of 

 pressure stimulate and may affect the consciousness. Even 



