272 DETAILED SYNTHESIS. 



649. THE CONTENTS OF THE CRANIUM, VIEWED ON 

 AT.T. SIDES, present the right and left cerebrum, cerebel- 

 lum oblongata, Pons, and commencement of twelve pairs 

 of nerves. 



650. THE CRANIAL GANGLIA, commonly called " the 

 BRAIN, the seat of the intellect, the will, the sensations, 

 and the emotions " (Leidy), viewed externally, form a, 

 large oval, spheroidal mass, shaped much like a duck's 

 egg, with a third of the under part of the smaller end re^ 

 moved, and, with the enveloping membranes, completely 

 fill the Cranium. 



651. THE BRAIN VARIES in size and form in different 

 persons and at different ages ; " the average weight in 

 males is fifty ounces ; in females, forty-five ; the maxi- 

 mum sixty-four, and the minimum twenty." Draper. 



652. Remark. It does not necessarily have the same form when 

 having the same size, for the parts of it are differently proportioned hi 

 different cases. The cerebellum averages one eighth the weight of the 

 whole ; it may be one third or one twelfth. Nor, if the proportional 

 weight of the parts and that of the whole are the same in two brains, is 

 it necessary that the particular forms of each should be the same. It 

 must be remembered THAT THE ONLY ESSENTIAL THING FOR EFFICIEN- 

 CY IN NERVOUS CENTRES are cells, communicating fibres, and a copious 

 supply of good Blood. 



653. IN EARLY LIFE the elasticity of a frame renders 

 other protection against jars of the Brain ^nnecessary ; 

 but as life advances, in addition to the increasing quan- 

 tity of marrow in the bones, the Brain requires some- 

 thing more. 



654. THE ARACHNOID MEMBRANE BENEATH THE 

 BRAIN increases in strength by addition to its sinewy 

 fibres, which, also in the form of areolar texture, grow 

 in between the arachnoid and pia mater, forming what 

 is called the subarachnoidean areolar texture, the areolas 

 of which are filled with serous fluid. 



649. What said of? 650. Viewed externally, what are ? 651. How f 

 652. W hat are f 65& What does brain require ? 654. What said of ? 



