348 



AVERAGE WEIGHT OF THE BRAIN IN THE 



experiments in 115 cases, in whicli he has both weighed the brain, and, subsequently, 

 gauged the skull in which it was contained. This large number of cases, which em- 

 brace persons of all ages from ten to ninety years, affords the most valuable materials 

 for testing the dilference between the cubic capacity of the cranium and the volume 

 of the encephala, and thus estimating the proper allowance to be made for the ab- 

 straction of membranes and fluids. And, in order to place these results in as 

 striking a light as possible, I have constructed the following table : 



The internal capacities of 115 skulls, tJie actual toeigJits of the irains contained in them, 

 their estimated weights, and the differences between the two, ivith the percentage allow- 

 ance to be made for membranes and fluids to maize the two agree. 



^ 







Capacity of 



Actual weight 



With addition 



Estimated 



Excess, -f-, 



Percentage 











sk'lls in cubic- 



of brains witli- 



of 14 grammes 



w'ght of brains 



or deficiency, 



allowance re- 





to 





centimetres. 



out membr'ns, 



to compensate 



17 p.c. haying 



— of estimat'd 



quired to be 



o 





Ages. 





fluids and me- 



for medulla 



been allowed 



weight, when 



made to bring 



Fh 



Ul 







dulla oblon- 



oblongata. 



for membr'nes 



comparedwith 



estim'dw'ght 











gata, in 





and fluids. 



real weight. 



nearest to 



£ 

















real weight. 



SZ 









Grammes. 



Grammes. 



Grammes. 



Grammes. 



+ 19-48 



Grammes. 



5 



c? 



10 to 19 y'rs 



1436-62 



1209-85 



1223-85 



1243-33 



18 p. c. 



75 



c? 



20 to 29 y'rs 



1535-52 



1327-43 



1341-43 



1324-72 



16-71 



16 p. c. 



9 



c? 



30 to 59 y'rs 



1556 96 



1316-12 



1330-12 



1347-18 



+ 17-06 



18 p. 0. 



11 



c? 



60 to 90 y'rs 



1550-43 



1227-21 



1241-21 



1321-91 



+ 80-70 



23 p. c. 



100 



c? 



10 to 90 y'rs 



1533-11 



1310-06 



1324-06 



1324-72 



+ -66 



17 p. c. 



15 



? 





1318-30 



1159-65 



1173-65 



1142-29 



31-36 



14 p. c. 



115 



?&c? 





1505-09 



1290-44 



1304-44 



1302-27 



2-17 



17 p. c. 



After the capacity of the skulls, as observed by Dr. Weisbach, and also the actual 

 weights of the brains, exclusive of membranes, fluids, and medulla oblongata, accord- 

 ing to his method of procedure, I have added a column in which fourteen grammes, 

 or about half an ounce avoirdupois, is restored to make up for the absence of the 

 latter structure, which is really contained in the cranial cavity, and therefore is re- 

 quired to be added to the weight of the brain. Dr. Robert Boyd informs us, as the 

 result of his extensive researches, that " the average weight of the pons varolii and 

 medulla varied in the males from 1-15 oz. to 1.02 oz., and from 1-05 to -95 oz. in the 

 females."* The mean of these weights is 1*04 oz., and the observations of Dr. Reid, 

 as quoted by Professors Quain and Sharpey,-|- that the two structures weigh conjointly 

 in men fifteen and three-fourths drams av., and in women one ounce and one-fourth 

 of a dram, coincide closely with Dr. Boyd's results. I have therefore regarded the 

 two structures to be of nearly equal weights, and made the uniform addition of half 

 an ounce, or fourteen grammes in every case to Dr. Weisbach's amounts, this being 

 as nearly correct on an average as may be. The next column of the table gives the 



* Op. cit., p. 261. 



t Elements of Aiiatomy, 5th ed., 1848, vol. ii, p. 672 



