DEFICIENCY IN INTELLECT FOUND TO 

 BE CORRELATED WITH DEFICIENCY 

 IN THE NUMBER OF BRAIN CELLS 



PATHOLOGISTS have known for 

 some time that imbecility de- 

 pends in part at least upon a 

 deficiency in the actual number 

 of cells of the higher cerebral regions. 

 Hammarberg in 1895 showed by actual 

 counting that such is the case. This 

 theory is supplemented and supported 

 by some recent work on the lesser-brain. 



"In the spring of 1916, while examining 

 the cerebellum of a general paralytic, 

 the writer' was first impressed by the 

 fact, familiar perhaps to most neuro- 

 pathologists, that in this disease there 

 is often a disintegration and disappear- 

 ance of a large number of the Purkinje 

 cells, leaving, however, the basket of 

 fibers which normally surrounds them. 

 Over a year later, while examining the 

 cerebellum of a microcephalic idiot, the 

 same scarcity of Purkinje cells was 

 observed, with the difference, however, 

 that the section did not show the same 

 evidence of the cells having become 

 reduced in number by disintegration; 

 the empty pericellular baskets were not 

 found as in the case of paresis; it seemed, 

 rather, that through some defect of 

 development the normal number had 

 never been present. 



"In order to get a fair basis for com- 

 parison, 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 men- 

 tioned. 



"Among the cerebella examined was 

 one of a man who had died at about 

 the age of sixty-five years after a pro- 

 tracted illness, and this, too, showed a 

 distinct loss of cells. So from this pre- 

 liminary 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 im- 

 probable 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 devel- 

 oped than that of lower forms, especially 

 with reference to speech, hand move- 

 ment, and the maintenance of equili- 

 brium while standing or walking. Alen.- 

 tal defectives generally show less motor 

 control along these lines, and it is de- 

 sirable that we know as far as possible 

 the neural basis for such lack of coordi- 

 nation. 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 import- 

 ance 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 cerebellum, which is not 

 generally associated with intelligent re- 

 actions as such." 



Dr. Ellis at the close of his article 

 comes to the conclusion that in low grade 

 mental defectives there is a distinct 

 deficiency either numerically or cytologi- 

 cally in a large percentage of the Pur- 

 kinje cells. He does not go into the 

 question of heredity, but he does con- 

 tend that practically all the cases are due 

 to some form of antenatal degeneration. 



1 Robert S. Ellis: "A preliminary quantitative study of the Purkinje cells in normal, sub- 

 normal and senescent human cerebella, with some notes on functional localization. The Journal 

 of Comparative Neurology, vol. 30, No. 2, February L5, 1919. 



369 



