74 THE EYE AND VISION. [OH. LV. 



(a.) Spontaneous or normal. 



(b.) A train of thought must first be set going ; as, for instance, converting 

 printed words into written characters. 



(c.) Mimetic ; he can only write from a copy. 



Two operations require the combined activity of both centres ; the first 

 of these is reading aloud, the second is writing from dictation. 



In reading aloud, the impression of the words enters by the ey.es, 

 reaches the visual word-centre, travels across to the auditory word-centre, 

 where the sounds of the words are revived and the person pronounces 

 them. 



Writing from dictation is just the opposite ; there the impressions of the 

 words enter by the ears, reach the auditory word-centre, travel across to 

 the visual word-centre, where the shapes of the words are revived and the 

 person writes them. 



In the investigation of any case of defective speech there are always the 

 following six things to be inquired into : 



1. Can the patient understand spoken words ? (The patient, of 

 course, not being deaf.) If he cannot, the auditory word-centre is 

 deranged. 



2. Can he repeat words when requested ? This tests the omission fibres 

 from the auditory word-centre which pass through the motor-centres for 

 speech in Broca's convolution. If he "cannot do this, the patient has 

 aphasia. 



3. Can he write from dictation? If he cannot, either the auditory or 

 visual word-centre, or the fibres passing from the one to the other, are 

 injured. 



4. Does he understand printed matter, and can he point out printed 

 letters and words ? Can he read to himself 1 (The patient, of course, not 

 being blind.) This tests the visual word-centre. 



5. Can he copy written words ? This tests the channels from the 

 visual word-centre to the motor-centres for movements of the hand in 

 writing. 



6. Can he read aloud, or, what is the same thing, name objects he sees ? 

 This is the opposite to writing from dictation, and tests the healthiness of 

 the word-centres or the fibres which connect the visual to the auditory 

 word-centre. 



CHAPTER LV. 



THE EYE AND VISION. 



THE eyeball is contained in the cavity of the skull called 

 the orbit ; here also are vessels and nerves for the supply of 

 the eyeball, muscles to move it, and a quantity of adipose 

 tissue. In the front of the eyeball are the lids and lacrimal 

 apparatus. 



The eyelids consist of two movable folds of skin, each of 

 which is kept in shape by a thin plate of fibrous tissue called the 

 tarsus. Along their free edges are inserted a number of curved 



