6o6 TEXT-BOOK OF PHYSIOLOGY 



of the class. This involves an analysis and a synthesis, a recognition of 

 the points of similarity and dissimilarity. The development of abstract 

 conceptions is believed to be associated with the activities of the cortex of 

 one or the other of the association areas (see page 610). 



For the emission of the sounds of words which constitute spoken 

 language it is essential that the sensations produced by the muscle move- 

 ments shall not only be perceived but registered or memorized. Without 

 this, the capacity to express words would not be possible. This registra- 

 tion is believed to be associated with the lower portion of the area for 

 muscle sensibility. 



2. The Emissive or Motor Phase. In an attempt to express ideas by 

 spoken or written language the muscles determining the action of the 

 larynx, jaws and teeth, tongue, lips, hands, etc., are excited to action 

 by nerve impulses descending through nerves, the nuclei of origin of 

 which lie in the gray matter beneath the floor of the medulla oblongata 

 and in the gray matter of the spinal cord. The nuclei of these nerves 

 are in turn excited to action by nerve impulses descending by way of 

 the internal capsule from the cortical areas for the face and arm 

 respectively. For this reason these areas may be designated the 

 executive centers, inasmuch as they execute the movement neces- 

 sary for speech. 



The Motor Speech Area. When it is desired to express ideas by means 

 of words (by speech) not only must the right words be selected, but they 

 must also be arranged in a logical order so that they will convey the ideas 

 to other people. This is accomplished by an area of the cortex which 

 has been termed the motor speech area, the function of which is to arrange 

 language for outward expression; for the use of the executive centers 

 concerned with speech, viz.: the laryngeal, lingual and facial centers 

 located at the foot of the pre-central convolution. This area, i.e., the 

 motor speech area, has been assigned to the posterior part of the sub- 

 frontal convolution (Broca's convolution) on the left side in those who 

 are right-handed and on the right side in those who are congenitally left- 

 handed, and in the anterior part of the insular or perhaps the pre-insular 

 convolutions. Unipolar faradic stimulation of this area fails to call forth 

 any motor response; its destruction by disease, however, is followed by a 

 more or less extensive loss of the faculty of articulate speech or the faculty 

 of expressing ideas with words, a condition usually spoken of as motor 

 aphasia or aphemia. This area and the area at the foot of the pre-central 

 convolution are united by association fibers. 



The Motor Writing Area. When it is desired to express ideas by 

 means of verbal signs (by writing) not only must the right signs be selected, 

 but they must be arranged in a logical order so that they will convey 

 the ideas to other people. This is accomplished by an area of the cortex 

 which has been termed the motor writing area, the function of which is to 

 arrange language for outward projection; for the use of the executive 

 centers concerned with writing, viz., the arm centers located in the 

 middle portion of the pre-central convolution. This area, i.e., the motor 

 writing area, has been assigned to the posterior half or third of the medi- 

 frontal convolution. Unipolar faradic stimulation of this area fails to 

 call forth any motor response; its destruction by disease, however, is followed 



