NERVOUS SYSTEM, 97 



Q. Why does so great a portion of blood go to the brain 

 in infancy? 



#. The predominance of the vital forces of the brain 

 invites it. 



Q. What is the comparative consistence of the brain in 

 foetal and senile life? 



& Nearly fluid in the foetus, it becomes quite firm in 

 old age, being progressive in its change from the fluid to 

 the firm state. The vascularity of the animal organs di- 

 minishes with age; their colour becomes dull. These 

 changes take place in the brain as well as nerves. 



Q. Give a brief account of the formation of the cerebral 

 mass. 



Ji. The hemispheres of the brain assume on their first 

 development the membranous form. The gray or cortical 

 substance is formed subsequently to the white. The me- 

 dullary substance of the brain, and the white substance of 

 the medulla spinalis, are filamentous and fibrous. The 

 structure of the cortical substance is not yet ascertained, 

 perhaps it is fibrous. 



Q. What is the chemical composition of the cerebral mass? 



Ji. It is composed of a white, shining fatty matter; of a 

 smaller portion of a red fatty substance; of water, albumen, 

 osmazone, sulphur, phosphate of potash, lime, magnesia, 

 with some appearances of muriate of soda. 



Q. State briefly Beclard's view of some points in the 

 nervous structure. 



#. He states that the nervous filaments do, at their ori- 

 gin, penetrate into the substance of the brain. The nerves 

 probably arise from the gray substance, not from the me- 

 dullary. The nervous filaments of the medulla oblongata 

 do decussate. The nervous texture is composed of globules. 



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