236 



Dr. J. B. Davis on the Weiyht of the Brain [Jan. 23, 



No. 8. Theophilus, reexamined in 1863. This is the most complete 

 drawing which I can make with my 6 -inch. I intended to repeat the 

 whole group. 



No. 9. The central mountain-group of Theophilus on a large scale. 18C3. 



No. 10. Posidonius, early morning. 1863. (Unfinished.) 



No. 11. Posidonius, nearer to midday. 1863. (Unfinished.) 



No. 12. Aristarchus and Herodotus. This is about the sixth drawing, 

 and exhibits in Aristarchus a double crater-wall, the inner one being sharp 

 and interrupted; a deep narrow fissure separates the two walls. The 

 interior surface is more moulded than in any drawings yetpubhshed. He- 

 rodotus, the dark crater, is merely sketched to give the course of the 

 seeming valley which conducts from it to the seeming delta. 



Januarij 23, 1868. 



Dr. WILLIAM B. CARPENTER, Vice-President, in the Chair. 



The following communications were read : — 



I. Contributions towards determining the Weight of the Brain in 

 the different Races of Man.'^ By Joseph Barnaed Davis, 

 M.D. &c. Communicated by Prof. John Marshall. Received 

 November 30, 1867. 



(Abstract.) 



It would naturally be expected that great attention had been directed 

 to the human brain, the organ of mental manifestation. Still little 

 has been done to ascertain its relative magnitude in the difPerect races of 

 mankind. Opportunities for examining exotic brains are rare, and it is only 

 by gauging the internal capacities of human skulls, and deducing the 

 weight of the brain, that data can be obtained. 



The inferiority of this method is not so clear as has been assumed, since 

 we are able to fix upon an unchangeable substance of definite specific 

 gravity for the purpose of this gauging, whereby we compensate for the 

 variable condition of the brain, depending upon disease and other causes, 

 and the immediate occasion of death. 



The great difficulty hitherto has been to decide upon a definite allowance, 

 or scale of allowance for other matters besides brain which always fill up 

 the cavity of the skull, in different proportions at different ages, &c. In 

 the present investigations it has been considered most advisable to fix upon 

 a definite, and at the same time proportionate, rule for compensating for 

 these fluids and membranes. And, after much inquiry, that rule has been 

 laid down as a general tare of 15 per cent, on the capacity af the skull. 



In former inquiries of this kind by Prof. Tiedemann and Prof. Morton, 

 this allowance has been entirely or almost entirely overlooked, by which 

 means their extended observations really refer to the internal capacities of 

 human skulls, and not to the weights of the brain, as they supposed. No 



