718 



AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



The anthropologists classify the encephala according to weight in the fol- 

 lowing manner : 



The Nomenclature of the Encephalon according to Weight. Weight in Grams 



(Topinard"). 



Classes. Males. Females. 



Macrocephalic From 1925-1701 From 1743-1501 



Large " 1700-1451 " 1500-1351 



Medium . " 1450-1251 " 1350-1151 



Small " 1250-1001 1150- 901 



Microcephalic " 1000- 300 " 900- 283 



The brain-weight in the majority of persons falls within the group of 

 medium brains, and average figures are obtained by combining the individual 

 records in which all variations from the medium occur. Of course races of 

 small size, like the small people of India or the Pygmies of Africa, would not 

 be expected to possess encephala equal in weights to those of the larger races of 

 Europe. Any set of average figures, therefore, should be based as nearly as 

 possible on observations made on a homogeneous population. Within the 

 limits of a given race there are several conditions which determine differences 

 in brain-weight, namely, sex, age, stature, and body-weight. 



From the observations by Dr. Boyd on the weight of the brain in England 

 the following table has been compiled : 



Table shounng the Weight of the Encephalon and its Subdivisions in Sane 

 Persons, the Records being arranged according to Sex, Age, and Stature 

 {from Marshall's tables based on Boyd's records). 1 



The method of weighing the brain used by Dr. Boyd 2 was as follows : The 

 skull-cap being removed and the pia being intact, the hemispheres were sliced 



1 a indicates that a record considered according to age is too large ; s indicates that a record 

 considered according to stature is too large. 



* Philosophical Transactions of the Royal Society, London, 1860 ; see also Marshall : Journal of 

 Anatomy and Physiology, 1892. 



