CHAPTEE XIII. 

 The Fokm-eelations of the Human Beain. 



Acquainted with the fundamentals which characterize the central 

 nervous system of vertebrates, we will now give our attention especially to 

 the mammalian brain. Seeing, as you have, how it has been slowly evolved 

 through a long series of transitional forms, it will certainly be gratifying to 

 investigate the entire structure, somewhat more thoroughly, in an example 

 of the highly specialized brains. The preceding description has directed 

 jowT attention principally to the morphology, and to some extent the psycho- 

 physiology, of the central nervous system. At present, however, we must 

 attempt to make good the demands which medicine, far advanced as it 

 already is in the diagnosis of nervous diseases, must necessarily make of the 

 physician. 



The old physicians have studied and described the human brain almost 

 exclusively; thus we have the best knowledge of its form-relations. The 

 numerous investigations on brains of those who have suffered intra vitam 

 from nervous affections, investigations which we again owe almost entirely 

 to physicians, have increased our knowledge to such an extent that it is now 

 possible, in a measure, to survey and describe the human central nervous 

 system more accurately — at least in its most important relations. 



Although these chapters are not intended for beginners, but for stu- 

 dents who are already acquainted in general with the grosser anatomy of the 

 human brain, it will not be entirely superfluous to review these relations. 

 These outlines of the map, on which later all the points of importance are to 

 be designated, are once more accurately established by recapitulating what 

 has previously been learned. Guided by embryology, you certainly will 

 easily understand the morphological relations presented by the adult organ. 



A fresh brain is laid on its base. You will notice at once the great 

 fissure which separates the hemispheres; and the fissure of Sylvius, which 

 arose with the development of the temporal lobe. Since the forebrain has 

 grown over most of the other parts of the brain (see Pig. 19), these latter 

 could be made visible posteriorly by raising up the hemispheres and un- 

 covering them. It can also be accomplished by separating and partially re- 

 moving the hemispheres. The second method is more advantageous, because 

 a better view of the lateral ventricles and the corpus striatum is thus ob- 

 tained. Let us, therefore, proceed in that manner. 



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