26 ROBERT S. ELLIS 



This set of results agrees with and corroborates the results 

 given in my previous paper. There is a gradual loss of cells 

 with advancing age, beginning normally at about the age of thirty 

 to forty years, although this probably varies in different individu- 

 als. The anterior (cephalic) part of the cerebellum, as repre- 

 sented by area 1, suffers more than the more posterior part, as 

 represented by area 3. This agrees with the results found by 

 Archambault ('18). 



Accompanying the actual loss of cells there are also degenera- 

 tive changes in those which remain. Chromatolysis, atrophy, 

 vacuolation, and homogeneous degeneration of nucleus and 

 cytoplasm are found. Pigment is likewise present at times 

 (DoUey, '17, '19), but I have not studied it carefully. 



Sex. The sex difference shown in chart 6 is one of which I 

 am not at all confident. As far as the results go, they indicate a 

 greater number of Purkinje cells in male cerebella. Men are of 

 course stronger than women, and experimental psychology shows 

 that they are capable of greater motor skill than are women 

 (Thompson, '03) ; so it is at least possible that there may be a 

 greater number of Purkinje cells in male cerebella. However, a 

 careful study of the sections used convinces me that the differ- 

 ence shown in the chart and tables is due to a greater loss of 

 cells in the female cerebella examined and that it is not a normal 

 difference. But a further study on better material will be neces- 

 sary to settle the point. 



There is no reason, at present, to think of the difference as 

 due to any systematic technical error. 



Comparison of right and left hemispheres 



Numerous attempts have been made to explain anatomically 

 the greater motor skill which the average person has with his right 

 (or left) hand. • Various estimates indicate that probably about 

 85 or 95 per cent of the population is naturally right-handed, 

 while the remaining 15 or 5 per cent is left-handed. According 

 to Ramaley ('14) right-handedness is a dominant Mendelian 

 unit character, while left-handedness is a recessive unit character. 



