tissue: estimates of this proportion vary. On the one hand we have Wingate 

 Todd's (1923, p. 265) statement, "Of course it is impossible to ascertain how 

 fully the brain ever occupies the total possible space at its disposal." On the 

 other hand figures are cited ranging from 10 per cent (Brandes 1927) to as 

 high as 33% per cent (cited by Mettler in his 1955 James Arthur Lecture). 

 Cranial capacity is therefore only an approximation to the size of the 

 brain itself. It might be deemed that we could simply apply a correction 

 factor to the determined capacity in order to ascertain the brain size. Un- 

 fortunately, the wide discrepancy between the 2 extreme figures cited— 10 per 

 cent and 33% per cent— would vitiate such a correction. Furthermore, the 

 ratio is not a constant figure within the adult lifetime of any one individual, 

 for the brain shrinks with age, in certain illnesses, and under some other 



Figure 8: Antero-superior view of a natural endocast of a presumed Austra- 

 lopithecus africanus from Sterkfontein. The pointers indicate a pair of 

 localized impressions where the surface of the endocast drops below the 

 surrounding intact surface, consequent upon a doubly indented de- 

 pressed fracture of the cranium. All trace of bone has since disappeared, 

 leaving only the indented surface of the endocast. 



9^ 



