822 



fact that it deeply penetrates the lieinisphere to supply the lateral 

 pail of the iiyperstriataiii indicates that this slniclure is pallial in 

 origin, as this vessel represents a greatly hyperlrophied pallial vessel. 

 The basal nucleus and inesostriatnm are supplied by palaeostriatal 

 arteries indicating that together these masses form the palaeostriatum. 

 Tiiis is in accordance with the ontogenetic studies on the bird's 

 brain of Ariëns Kappkrs. 



In this way the subdivision of the bird's brain may be linked 

 up with those of the re|>lile and so, from work already published, 

 homologised witli the constituents of the corpus striatum of mammals. 

 The |)alaeostriatiim of birds, represented by the palaeostriatum 

 priiiiidinn)!. and the jxihieoxtriatum auginentatuin , is homologous with 

 the globus pallidus of mammals. The hyperstriatnm corresponds to 

 the i)u(amen and caudate nucleus (neostriatum of Akiëns Kappers). 

 Though the hyperstriatum in most birds is divided by the lamina 

 mednlliiris hyjiei-Mriati into the liyperstrintuni siiperhis -dnd {he hi/per- 

 striatuin iii/erius the sections under review do not exhibit this sub- 

 division. Akiëns Kappers believes that the hi/perstriatiim inferms 

 corresponds with the putamen and caudate nucleus of mammals and 

 that a possibility exists that the lajperstiiaimn, super/iis repi'esenis 

 the claustrum which is also hypopallial in origin. The archislriatum 

 forms the hypopallial part of the nucleus amygdalae. 



The forebrain acts upon the brain-stem by the ventral forebrain 

 bundle, and upon the ganglion habenulae by the olfaclo-habenular 

 tract. The sti'io-mesencephalic, occipilo-uiesencephalic, and septo- 

 mesencephalic tracts connect it with the mesencephalon. The corpus 

 striatum recreives the external and medial thalamofrontal tracts from 

 the nuclens rotmubis and «^/c'/é?'/.y f/crxrt//.; of the thalamus respectively. 

 Accompanying the external ihalamo-froiital tract is i he dorsal supra- 

 optic commissure. The etierent mechanism of the corpus striatum 

 consists of the direct and crossed internal strio-thalamic tracts which 

 terminate in the ventral thalamus and mid-brain. 



LETTERING USED IN THE FIGURES. 



A. prp. Area praepiriformis. 



B. olf. Bulbus olfactorius. 



C. t. s. Gommissura telencephali superior. 

 Gap. ex. Gapsula externa. 



Cap. h. Gaput hyperstriati. 



Cblm. Cerebellum. 



Cer. H. Gerebral hemisphere. 



Co. Cortex. 



