258 



ORIGINAL ARTICLES AND CLINICAL CASES 



convexity of the occipital pole. Fig. 2 is a composite diagram of the 

 lesions in nine animals in which habits of visual discrimination persisted 

 after bilateral injury. Detailed descriptions of these animals have been 

 given in previous papers [10, 11]. In each animal the area destroyed 

 included about one-fourth the blackened area of the diagram. Fig. 3 

 is a composite diagram of the lesions in seven animals which lost the 

 habit of visual discrimination after operation. These two series of 

 animals show clearly the restriction of cortical function in vision to the 



Fig. 1. — Composite diagram of the electro-stimulable points on the cerebral cortex of 

 the rat. a = Head turned to opposite side, b = Nose retracted, c — Vibrissa? moved. 

 d = Chewing movements, c = Tongue protruded. / = Eye closed, g = Ear adducted. 

 h = Ear erected, i = Shoulder drawn forward, j = Fore-arm retracted, k = Elbow 

 flexed. I =Elbow extended, m = Wrist flexed, n = Fore-arm rotated, o = Back flexed 

 to opposite side, p = Hind leg drawn forward, q = Homolateral leg flexed, ipselateral 

 extended, r = Ankle extended, s = Tail drawn to opposite side. All movements are 

 contralateral to the hemisphere stimulated, except where indicated. 



occipital pole and the survival of the habit after destruction of the 

 motor area. The area included in fig. 3 corresponds roughly to 

 Brodmann's area striata in other rodents [2]. 



The corpus striatum in the rat is very large in proportion to the 

 volume of the cerebral cortex. Fig. 4 shows it in frontal and hori- 

 zontal sections through the levels used in later diagrams. The caudate 

 nucleus consists of masses of cells scattered among the fibres of the 

 internal capsule and is nowhere distinct from the descending fibres. 

 The lenticular portion is relatively free from pyramidal fibres. The 



