CEREBRAL FUNCTION IN LEARNING 119 



tex was bilateral, as in numbers 38*, 39*, 14, and 19, or unilateral, ) 

 as in the others. 



But the immediate reference of the paresis to the corpus stri-\ 

 atum was prevented by the fact that many of the annuals which / 

 gave no indication of motor disturbance showed more or less ex- j 

 tensive injuries to the corpora striata. This made necessary the./ 

 reexamination of the entire mass of material to determine the 

 exact character of the lesions to the corpora striata in each case. 

 The results of this are summarized in table 10. The lesions were 

 worked up without reference to the behavior of the animals and 

 classified as bilateral, unilateral, slight, and extensive. They 

 were then coordinated with the behavior material. The result * 

 is a striking correspondence between extensive lesion to one cor- 

 pus striatum and the appearance of the paresis. The table / 

 shows that no animal with bilateral injuries developed paresis: 

 that no annual with slight injury to one corpus striatum devel- 

 oped paresis: that all but one animal (number 36*) with exten- 

 sive destruction of one striate body showed pronounced hemi- 

 paresis. Horizontal sections from the brains of typical cases in 

 each of these three groups are shown in plate IV, in which the fig- 

 ures bear the experiment numbers of the series of Lashley and 

 Franz. Similar sections of all of the annuals of the present series 

 are given in plates I and II. From these a good idea of the actual 

 extent of the injuries can be obtained. 



Of the animals with extensive lesions to one striate nucleus only 

 number 36* failed to show pronounced paresis. A review of the 

 original description of this animal revealed the fact that the ani- 

 mal had an initial preference for the right turn in the simple 

 maze. A similar tendency to turn to one side occurs in all 

 paretic animals and is much less frequent in normal animals. 

 Further the direction of turning is that which most frequently 

 results from right paresis (lesion in left hemisphere) so that it 

 appears that this animal had a slight paresis which had remained 

 undetected. If this interpretation is correct, it seems that every 

 animal of the series which had an extensive destruction of one 

 corpus striatum developed hemiparesis, and that this lesion is the 

 only one of those recorded which does produce motor disturbance. 



