220 CENTRAL NERVOUS SYSTEM 



may to a considerable extent be regained, and this may be due 

 to powers residing in the right speech centre. 



In sensory aphasia the perceptive factor in speech is deranged. 

 In ordinary cortical sensory aphasia the patient cannot under- 

 stand spoken or written language. He may talk incessantly 

 but the series of words, correctly enunciated, have no connected 

 meaning or may be a mere jargon not composed of known 

 words at all. This condition is associated with lesions in two 

 distinct regions of the brain. If the upper portion of the tem- 

 porosphenoidal lobe is damaged, then the spoken word is missed, 

 the written word is understood. This is word deafness. On the 

 other hand, when the lesion lies in the occipital region then 

 spoken words are understood and written words not at all. 

 This is word blindness. Sensory, like motor aphasia, may exist 

 in all degrees of completeness and both may exist together. 



Weight of Brain. Roughly it is- three pounds, or about one- 

 fortieth .of the total body weight, and this ratio is greater than 

 in the lower animals, with a few exceptions among the smaller 

 birds and monkeys. 



WEIGHT OF BRAIN IN GRAMS (TOPINARD) 



Classes. Males. Females. 



Macrocephalic 1925 to 1701 1743 to 1501 



Large . 

 Medium . 

 Small . . . 

 Microcephalic 



1700 to 1451 1500 to 1351 



1450 to 1251 1350 to 1151 



1250 to 1001 1150 to 901 



1000 to 300 900 to 283 



In comparing brain weights, the method of removal of the 

 encephalon should always be considered, since retention of 

 pia and the fluids of the ventricles affects the result. 



In Boyd's method, after the skullcap has been removed but 

 the pia left intact, the hemispheres are sliced away in hori- 

 zontal sections as far down as the tentorium. By means of a 

 section passing in front of the corpora quadrigemina the re- 

 mainder of the hemispheres is removed. The cerebellum, 

 including the quadrigemina, pons, and bulb, is finally removed. 

 Each portion is weighed separately. Sometimes the pia and 

 the fluid within the ventricles are included in the weight of the 

 brain, and sometimes not. Broca gives the following table for 

 the weight of the pia, for normal males : 



