THE STORY OF THE BRAIN AND NERVE 125 



that the right speech centre, hitherto dormant, has 

 come into play. 



THE SENSES. The senses are estimated to be five 

 in number, including, sight (Fig. 35), hearing (Fig. 

 36), touch, taste, and smell. It is, however, most 

 probable that we possess a sense of weight, and also 

 that of temperature or heat. Some authorities incline 

 to believe in the existence of other senses, amongst 



f Coptic nerus 

 posterior chamber. 



Fig. 35. SECTION SHOWING STRUCTURE OF THE EYE. 



them a sense of direction still imperfectly developed 

 in man. The senses are mere "gateways of know- 

 ledge" in other words, they simply receive inform- 

 ation from the outer world, modify it, and transmit 

 to the corresponding centres in the brain, 

 which in turn pass forward the information to be 

 submitted for judgment by the intellectual centres. 

 Thus we do not really see with the eye or hear with 

 the ear. Seeing and hearing represent intellectual 

 acts to which the work of the eye and ear is only a 



