THE BRAIN. 209 



This is divided into two equal parts, longitudinally, 

 called the right and left hemispheres of the brain h h h, 

 Fig. 120, which represents the right hemisphere. The 

 medulla oblongata, m, or oblong marrow, is that portion 

 of the spinal chord which is contained within the skull. 

 Its continuation downwards, s, is called the medulla spi- 

 nalis, or spinal marrow. The part c, is the cerebellum, 

 or little brain, so called to distinguish it from the cere- 

 brum, above described. The tree-like figure, shown by 

 dividing it through the centre is called the abor vita, or 

 tree of life. The corpus callosum, or hard body, q, is a 

 white medullary part, which joins the two hemispheres 

 together ; v, marks one of the lateral ventricles of the 

 brain. The pineal gland p, was supposed by Des Car- 

 tes to be the seat of the soul. 



It is not within the scope of this work to enter into a 

 minute description of the different parts of the brain ; 

 our object being to give a general, rather than a partic- 

 ular account of its structure and functions. 



All the nerves are considered as originating either 

 directly or indirectly from the medullary substance, that 

 is, from the medulla oblongata, or the spinal chord. 

 Those which pass through the bones of the skull, are 

 however, called cerebral nerves, while those which arise 

 from the spinal marrow are called spinal nerves. Among 

 the first are the optic and olfactory nerves. 



The brain receives a larger quantity of blood than 

 any other organ of the same size. The arteries for this 

 purpose, are four in number, and are supposed to convey 

 to the brain an eighth part of all the blood which flows 

 from the heart. 



PHRENOLOGY. 



Physiologists have been at great pains to ascertain 

 what parts of the brain are the particular instruments of 



What part of the brain is the cerebrum 1 What are the hemispheres 

 "of the brain 1 What is the medulla oblongata 1 What does the continu- 

 tion of this part form 1 What is the situation of the cerebellum 1 From 

 what parts do the nerves arise 7 What is said of the quantity of blood 

 sent to the brain ? 



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