STUDY OF BRAINS OF SIX EMINENT SCIENTISTS AND SCHOLARS. 221 



from without was one of the factors which determined the doHcho-cephahc type of the 

 ohler stock. Prognathism becomes more and more checked the higher we go in the 

 scale, and the superior, brainier individuals of the higher races therefore exhibit less 

 prognathism and greater breadth of skull. 



We find corroboration of these general statements in the compai-ative study of the 

 brains and skulls of men of notable intelligence with those of the ordinary population, 

 or of the highly civilized with savage tribes. Many writers have laid stress upon the 

 apparent relation between stature and the intellectual differences of the races of man, 

 their hasty conclusion being that stature had everything and brain-size nothing to do 

 with mental capacity. Though it be granted that the taller Anglo-Saxons have 

 heavier brains than the shorter Hindoos or Bushmen, a further analysis shows this 

 rule to be untenable in the case of other races, notably the Mongolians and their kin, 

 the Eskimos. Brain-weight is influenced by many factors, including age, sex, race, 

 stature, cranial capacity and form, body-build, state of nutrition and mode of death. 

 Brain-weight statistics therefore must be judged with care. It is difficult to give an ex- 

 act expression of the inter-relation between brain-size and mental capacity. Professor 

 Manouvrier, in 1882, attempted to estimate numerically the two factors in the bulk 

 of the brain, i. c, size of the body and the degree of the intelligence ; his formula 

 gave concordant results as a rule, but broke down when applied to extremes. Pro- 

 fessor Dubois, in 1897, proposed a different method. He started with the assumption 

 that the brain consists entirely of central parts of the reflex arcs, the function of which 

 is to bring sensory and motor nerves into relation with each other and he concluded 

 that in animals presenting the same degree of physical development the number and 

 weight of these reflex arcs would be proportional, approximately, to the number of 

 sensory nerve-fibers. In two animals in very different stages of psychical evolution 

 but of the same bulk, and having therefore approximately the same number of sen- 

 sory fibers, the animal in whom the central parts of the reflex arcs attain the greater 

 degree of complexity will have the heavier brain. It appears from the researches of 

 Dubois that the cube root of the square of the weight of the animal multiplied by a 

 constant which varies with each species expresses with fair accuracy the relative size 

 of the surface of the body. If S and s be the weight of the body of two animals their 

 surfaces will be 



^S^ and ^J or ^S""" and s°-^. 



In practice the factor is not exactly 0.6 but 0.56, the extremes being 0.54 and 0.58; 

 thus 



