230 ROBERT S. ELLIS 



a fair basis for comparison, a number of cerebella were studied 

 and the relative frequencies of cells noted. In some of the cases 

 the cells appeared to be almost uniformly distributed and with 

 few large spaces between them; others showed losses similar to 

 the two cases already mentioned. 



Among the cerebella examined was one of a man who had died 

 at about the age of sixty-five years after a protracted illness, and 

 this, too, showed a distinct loss of cells. So from this preliminary 

 set of observations it seemed clear that the number of Purkinje 

 cells is variable under different conditions. 



It is well known that in paresis, in extreme old age, and in 

 low grades of feeble-mindedness there is ordinarily a considerable 

 degree of deficiency in motor coordination. The question con- 

 sequently arose, how far is it possible to find differences in the 

 number of cells that will account, partially at least, for the 

 observed differences in behavior? 



The writer's primary interest at the time of taking up this 

 investigation lay in the question of the anatomical basis of mental 

 defect, and it seemed not improbable that a careful study of the 

 Purkinje cells might throw some light on one of the most evident 

 deficiencies found in such cases. The human motor mechanism 

 is much more highly developed than that of lower forms, 

 especially with reference to speech, hand movement, and the 

 maintenance of equilibrium while standing or walking. Mental 

 defectives generally show less motor control along these lines, 

 and it is desirable that we know as far as possible the neural 

 basis for such lack of coordination. 



A further reason for making a study of the cerebellum in such 

 cases is found in the fact that a number of writers, especially 

 Tredgold ('03) and Bolton ('03, '10) in England, have em- 

 phasized, perhaps unduly, the importance of the frontal lobe of 

 the cerebral cortex as the area particularly affected in amentia. 

 It accordingly seemed worth while to determine whether the 

 brains of aments show defects in other parts, such as the cere- 

 bellum, which is not generally associated with intelligent 

 reactions as such. 



