PHRENOLOGY. 205 



637. This is divided into two equal parts, longitudinal- 

 ly, 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 cord which is contained within the scull. Its 

 continuation downward, s, is called the medulla spinalis, 

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

 brain, so called to distinguish it from the cerebrum, above 

 described. The tree-like figure, shown by dividing it 

 through the centre, is called the dbor 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 Cartes to be the seat of 

 the soul. 



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

 a minute description of the diiferent parts of the brain ; 

 oar object being to give a general, rather than a particular 

 account of its structure and functions. 



639. All the nerves are considered as originating either 

 directly or indirectly from the medullary substance, that is, 

 from the medulla oblongata, or the spinal cord. Those 

 which pass through the bones of the scull, 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. 



640. 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 con- 

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

 flows from the heart. 



PHRENOLOGY. 



641. 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 ? What are the hemispheres of 

 the brain ? What is the medulla oblongata ? What does the continuation 

 of this part form ? What is the situation of the cerebellum ? From what 

 parts do the nerves arise ? What is said of the quantity of blood sent to 

 the brain? 



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