THE MAMMALIAN NERVOUS SYSTEM 103 



(5) The corona radiata. This name is given to those fibers 

 which run between the cortex and the underlying parts of the 

 brain stem. Most of them run through the internal capsule of 

 the corpus striatum (see Sections 138, 139, 144, 145, and Her- 

 rick ('18), Figs. 77, 79, 80). They include the projection fibers 

 of the great sensory systems from the thalamus, various 

 other thalamo-cortical connections, the voluntary motor corti- 

 cal tracts (including the pyramidal and cortico-bulbar tracts), 

 and the cortico-pontile tracts. These fibers are named from 

 the fact that they diverge from the upper border of the internal 

 capsule like the rays of a crown. In the dissection at this stage 

 the broken ends of the vertical corona radiata fibers are seen 

 breaking through the transverse sheet of callosal fibers which 

 run at right angles to them. The cingulum and other longitud- 

 inal association tracts of the hemisphere run at right anglef to 

 both of these systems 



120. Association tracts of the human brain. In the human 

 brain tease away the tissues on the dorsal and lateral walls of 

 the hemisphere and dissect out: 



(1) short association fibers 



(2) fasciculus longitudinalis superior 



(3) fasciculus occipito-frontalis inferior 



(4) fasciculus uncinatus 



(5) fasciculus transversus occipitalis 



(6) fasciculus longitudinalis inferior 



(7) the cingulum 



These represent a few only of the more clearly defined asso- 

 ciation bundles, of which the white matter of the hemispheres 

 is largely made up. While making these dissections note 

 the relations of the fibers of the corpus callosum and of the 

 corona radiata. In well-preserved brains these tracts can be 

 dissected out with great completeness (see Section 141). Even 

 in poorly preserved brains some of them can usually be demon- 

 strated. See: Barker ('01), Chap. LXVII, pp. 1058-1069; 

 Cunningham ('15), Figs. 577, 578, pp. 649, 650; Curran ('09); 

 Gray ('18), Fig. 751; Herrick ('18), Fig. 121; Howell ('15), 

 Fig. 83, p. 185; Morris ('14), Figs. 701, 702, p. 891; Quain ('09), 

 Vol. Ill, Pt. I, Fig. 323, p. 359; Toldt ('04), Figs. 1230, 1231; 

 Villiger ('12), Figs. 124-127, p. 134. 



