THE NERVOUS SYSTEM. 



307 



shall find the surface farther augmented by cavities, and the sur- 

 face of these cavities also increased by irregularities. 5 



On cutting the hemispheres of the cerebrum away by succes- 

 sive horizontal slices, we find the mass white and the outermost 

 portions grey. When the hemispheres are entirely removed, a 

 continuous surface remains, called centrum ovale ; the two halves 



The cranium is external. The pulpy grey substance next. Then the fibrous 

 white substance or centrum ovale. The mesolobe in the midst of it ; and the 

 raphe in the centre of this. 



b M. Desmoulins contends, 1st, that integrity of surface is the only condition 

 constantly necessary for the production of nervous actions j 2d, that these are 

 proportionate to extent of surface ; and, 3d, that they are performed by the sur- 

 face, and transmitted from it. The energy of an electric apparatus depends very 

 much upon surface. Dr. Spurzheim asks whether it is not on this account that 

 the encephalic masses are hollow or convoluted ; and remarks that the nervous 

 masses of the lower animals are very commonly hollow. The Anatomy of the 

 Brain, by G. Spurzheim, M.D., p. 206. London, 1826. 



Dr. Macartney has lately declared that the surface of the human brain is thus 

 proportionately more extensive than that of any other animal. Second Report of 

 the British Sclent. Assoc., p. 454. 



Y 3 



