CENTRES FOR THE EXPRESSION OF IDEAS IN LANGUAGE 591 



language. In cases of aphasia it often is difficult to determine this 

 point. In certain cases it is possible that the individual may under- 

 stand what is said and may form ideas to which he is unable to give 

 verbal expression. In such instances he can neither speak nor write. 

 There are certain cases in which written or printed words convey no 

 idea, while spoken words are understood, but there is no loss of intelli- 

 gence and words are spoken without difficulty. This condition is called 

 word-blindness. If there is simple want of coordination of the muscles 

 concerned in speech, words are spoken that may have no connection 

 with the idea to be conveyed, but the individual may be able to express 

 himself in writing. This condition is known as ataxic aphasia. The 

 inability to express ideas in writing is called agraphia, and this usually 

 is an indication of the condition known as amnesic aphasia, in which it 

 is impossible to put ideas into words in any way. In this condition 

 there is loss of memory for words, as its name implies. Persons affected 

 with purely ataxic aphasia may understand and write perfectly, but they 

 can not read aloud or repeat words or sentences spoken to them. In 

 cases of simple amnesic aphasia, patients can sometimes repeat dictated 

 words. In cases in which hemiplegia is marked, the aphasia usually is 

 ataxic. In cases in which there is no hemiplegia, the aphasia usually 

 is amnesic. The ataxic and amnesic forms of aphasia may be combined. 

 A full description, however, of the many and varied forms of aphasia 

 would be out of place in this work. 



In 1766 Pourfour du Petit reported a case of aphasia, with lesion of 

 the left frontal lobe of the cerebrum, in which the patient could pro- 

 nounce nothing but " non" 



Marc Dax (1836) indicated loss or impairment of speech in one hun- 

 dred and forty cases of right hemiplegia. These observations attracted 

 little attention, until 1861, when the subject was studied by Broca. Since 

 then, many cases of aphasia with lesion of the left frontal lobe have been 

 reported by various writers. In 1863 M. G. Dax, a son of Marc Dax, 

 limited the lesion to the middle portion of the left frontal lobe. It was 

 further stated by Broca and Hughlings Jackson to be that portion of the 

 brain nourished by the left middle cerebral artery (the inferior frontal 

 branch). According to recent observers, the most frequent lesion is in 

 the parts supplied by the left middle cerebral artery, particularly the 

 lobe of the insula, or the island of Reil ; and it is a curious fact that this 

 part is found only in man and monkeys, being in the latter but slightly 

 developed. 



While the cerebral lesion in aphasia involves the left frontal lobe in 

 the great majority of cases, there are instances in which the right lobe 

 alone is affected, and these occur in left-handed persons. Aside from 



