CENTRA L NER I T) I T S S ) ' V TEM. 



275 



The specific gravity of the entire encephalon is for the male, 1036.3, and 

 for the female, K).'5ii. 



Weight of the Encephalon. — The encephalon is that portion of the 

 central nervous system contained within the skull. The accompanying dia- 

 gram (Fig. 117) shows the encephalon, together with one manner of sub- 

 dividing it. Its weight has usually been taken while it was still covered by 

 the pia, but after allowing the fluids to drain away for five minutes or more. 

 Sometimes drainage has been facilitated by cutting into the brain; hence, 

 when the brain-weight records by any observer are to be discussed, the first 

 question concerns the method according to which the brains were examined, 

 for the weights may be either with or without the pia and with or without 

 drainage. 



The anthropologists classify encephala according to weight in the follow- 

 ing manner : 



The Nomenclature of the Encephalon according to Weight. 



(Topina rd.) 



Classes. Males. 



Microcephalic From 1925 to 1701 



Large " 1700 to 1451 



Medium " 1450 to 1251 



Small " 1250 to 1001 



Microcephalic " 1000 to 300 



Weight in Grams. 



Females. 

 From 1743 to 1501 

 " 1500 to 1351 

 " 1350 to 1151 

 " 1150 to 901 

 " 900 to 283 



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

 the following table has been compiled : 



Table showing the Weight of the Encephalon and its Subdivisions in Sam- 

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

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



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

 considered according to stature is too large. 



