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MANUAL OF HISTOLOGY. 



base of the brain is also divided into a series of basal frontal, 

 temporal and occipital convolutions. By far the most impor- 

 tant region of the cortex-, according to our present knowledge, 

 is that along the fissures of Sylvius and Rolando, the so-called 

 motor tract of the hemispheres. The exact physiological func- 

 tions of the anterior frontal, the occipital, temporal, and basal 



Fio. 149. Modified from Ferrier ; letters and figures the same : 8, fissure of Sylvius ; c, fissure of 

 Ronaldo ; po, parieto-occipital fissure ; A, ascending frontal gyrus ; B, ascending parietal gyrus ; F 2 , 

 third frontal gyrus; P a ', gyrus angularis ; circle I., seat of lesions which (on the left) cause aphasia; 

 circle II., seat of lesions which convulse or paralyze the upper extremity of the opposite Bide; dotted 

 circle III., seat of lesions which probably convulse or paralyze the face on the* opposite side; dotted oval 

 IV., seat of lesions which probably convulse or paralyze'the lower extremity of the opposite side. These 

 districts receive their blood-supply chiefly from the middle cerebral artery. From Lectures on Localiza- 

 tion by Dr. E. 0. Seguin : N. Y. Medical Record, October 19, 1878, p. 301. 



regions of the hemispheres, is not known, inference, however, 

 making them the seat of general and special sense, vaso-motor, 

 psychic centres, etc., etc. 



The middle or f ronto-parietal region, however, is the proven 

 seat of motor centres for the face, limbs, and body, and the 

 faculty of articulate language. The centre for speech occu- 

 pies the region at the base of the third frontal convolution 

 and the island of Reil on the left side, a similar location on 

 the right side being occupied by a centre for articulatory 

 movements. A little higher on the ascending frontal and 

 parietal convolutions is an area having control over the move- 

 ments of the tongue and face. Still higher is found a larger 

 space, the centre for the arm of the opposite side. A larger 

 space at the junction of the fissure of Rolando and the su- 



