158 



The first part contains the basal miclens or ixilaeostriatum primi- 

 tivum (its only constituent in Amphibia) and the mesostriatiim which 

 developes from the same mass as tiie basal nucleus including the 

 surrounding tissue {palaeostrintum augmentatum). 



The total palaeostriatum in man is represented by the globus 

 pallidus and eventual vestiges of grey substance occurring in and 

 mesially to tlie capsula interna (undernealh the fiss. neo-pulaeostriatica) 

 including a vestige of grey substance which is a continuation of 

 the latter and (as in birds) lies underneath the caudate, nucleus: 

 the substantia palaeo^triatica caudata, which in some animals may 

 be separated from the caudate nucleus by a continuation of the 

 lamina medullaris externa and of the fiss. neo-palaeostriatica. The 

 palaeostriatum arises entirely from the base of the forebrain near 

 the anterior wall of the preoptic recess. It consequently is entirely 

 telencephalic in character not of diencephalic origin as Spatz ') 

 supposes, though its cells in adult animals may be continuous with 

 the ventral and peduncular cells of llie thalamus and midbrain as 

 1 already pointed out in 1908'). 



The neostriatum (putamen and caudate nucleus) in mammals, 

 arises as well from the base of the brain in front of the palaestriatum 

 (immediately behind the anterior olfactory ventricle) as from the 

 adjacent pallium (Ei,L. Smith). The partly pallial origin of the 

 neostriatum (already supposed — but not proved — by Weknicke(?), 

 Obkrsteineh and Köli.iker) explains the fact tiiat in many cortical 

 affections of the brain frontal lobe chiefly) as general paralysis 

 (Mills, L. Bouman, Forstek, Gans) also the neostriatum is often affected, 

 more often than the palaeostriatum. 



Whether the hyperstriatum superius ot birds which arises only 

 from the mantle is included in the neostriatum in mammals or not, 

 cannot as yet be settled with certainty. 



The possibility exists that it is represented in mammals and man 

 by the clausirum, which also is a ventricular ingrowth of the 

 pallium (a hypopallial product in the sense of Ell. Smith, I.e.). 



Difference must be made between a cortical ingrowth and a (hypo) 

 pallial ingrowth. Both are formed in the mantle, but need not 

 necessary to be related, though a pallial ingrowth may be followed 

 by a cortical ingrowth (as fi. is seen witii the amygdala). 



1) Ueber Beziehungen zwischen der Substantia nigra des Mittelliirns und dem 

 Globus pallidus des Linsenl^erns. Erg. Heft zum Anat. Anzeiger Bnd. 55, 1922. 



') Weitere Mitteilungen ueber die Phylogenese des Corpus Striatum and des 

 Thalamus, Anat. Anzeiger Bnd. XXX, 1908. 



