THE CEREBRAL HEMISPHERES 



913 



The axones of corticifugal neurones proceed to the nucleus of the superior quadri- 

 geminal body along the optic radiation. 1 



Some fibres are detached from the optic tract and course through the cms 

 cerebri to the oculomotor nucleus. These fibres are small, and are believed to be 

 afferent branches for the Sphincter papillae and Ciliary muscles. 



The connections of the external geniculate body and pulvinar with the higher 

 cortical centre of vision are established by neurones, the cells of which lie in the 

 two ganglia just mentioned, and whose axones stream in an arched, more or less 

 compact bundle in the white substance of the cerebral hemisphere toward the 

 occipital cortex. Another system of neurones, whose cells lie in the cortex, sends 

 its axones in the reverse direction (corticifugal) to the two lower centres. The 

 cerebral tract thus formed between primary and secondary (cortical) centres is 

 called the optic radiation, to be studied more fully in the sequel. The components 

 of the optic path are delineated schematically in Fig. (>n'S. 



The Cerebral Hemispheres. 



External Morphology. Of all the component parts of the brain, the cerebral 

 hemispheres form the largest part, and their preponderance and remarkable 

 specialization underlie the extraordinary manifestations of the intellect so highlv 

 amplified in man. 



MEDICOMMISSURC 



CHOROID PLEXUS OF 

 THIRD VENTRICLE 



TENIA THALAMI 



OSTRUW 



COPULA 

 PRECOM- 

 MISSURC 



TERMA 



CHI ASM 



O PT I C 

 NERVE / 

 HYPOPHYSIS 



/OCULOMOTOR 

 / NERVE 

 / ALBICANS 

 TUBER 



AQUEDUCT 

 xVALVULA 



\FOURTH 



VENTRICLE 



Fin. 069. -Mesal aspect of a brain sectioned in the median sagittal plane. 



The term cerebrum, often employed loosely as embracing several brain parts, 



s here intended to include the brain mantle and the olfactory lobe equivalent to 



the telencephalon of His, with the exception of the pars optica hijpothalami. As 



58 



