THE NERVOUS SYSTEM. 



539 



the two halves of the pallial expansion (Fig. 471, be)] (2) the boundary line or 

 line of union with the thalamus lying caudally (pallio-thalamic boundary) 

 (Fig. 471, cd}\ (3) the boundary between pallium and corpus striatum (strio- 

 pallial boundary) (Fig. 471, bd). The boundaries of the future corpus striatum 

 are (i) the median (Fig. 471, ab), (2) the strio-pallial (Fig. 471, bd), (3) the 

 strkKhalamic or peduncular (Fig. 471, de) and (4) the strio-hypothalamic (. . r ig. 

 471, ae). The internal prominence which is the rudiment of the coipus 

 striatum, has three limbs or crura, (i) a ridge proceeding forward (anterior 

 crus), which corresponds externally to the furrow (external rhinal furrow) 

 fojming the lateral boundary of the anterior olfactory lobe, (2) a middle crus 



Prosencephalon 

 (Fore -brain) 



Rhinencepha 



Corpus striatum 



Corpora quadrigemioa 



Peduuculus cerebrl 



Brachium conjunctive 



and velum medullare 



aoterius 



Pars optica liypothalarai 

 Pai-s mamillaris hypothalami .. 

 Pons [Varolil 



Pars ventralis - 

 Sulcus limitans- 



(Lozenge- shaped 

 brain) 



Cerebellum 



FIG. 471. From a model of the brain of a human embryo at the end of the first month, right 

 half, seen from the left. His, Spalteholz. 



corresponding to the constriction separating the two olfactory lobes, and (3) a 

 posterior crus corresponding to the posterior boundary of the posterior olfactory 

 lobe. This latter is merged with the earlier furrow separating the telencephalon 

 from the thalamus and hypothalamus (peduncular furrow). What may be 

 called the main body of the corpus striatum, from which these limbs radiate, 

 soon becomes expressed externally by a shallow depression in the lateral sur- 

 face of the hemispheres immediately dorsal to the olfactory lobes. This 

 depression is the first indication of the /0ssa Sylvii (Fig. 465) . 



The boundaries of the pallial hemisphere above indicated are identical 

 with the boundaries of the future /0r#wW 0/M<wr0. 



The median lamina uniting the two halves of the pallium and the two corpora 

 striata may be termed the lamina terminates and represents the roof plate and 

 floor plate of this region. The point of meeting of the roof plate and floor 



