328 NORMAL HISTOLOGY. 



gain the cortex, however, do not correspond exactly with those enter- 

 ing the cerebrum as the peduncular bundles, since some of the latter 

 are deflected and pass to the caudate and the lenticular nucleus from 

 the internal capsule ; on the other hand, the peripherally-streaming 

 bundles are augmented by fibres which come from the thalamus and 

 the subthalamic region. The peduncular tracts continued to the 

 cortex consist principally of the pyramidal fibres, the fibres from 

 the caudate and lenticular nuclei, and the fibres to the temporo-occipi- 

 tal region from the optic thalamus and the pons. 



The tracts of the tegmentum largely contain fibres related to 

 the connections of the thalami, the cerebellum, and the corpora 

 quadrigemina ; regarding the exact course and communications of 

 these bundles much still remains to be determined. 



Two small but remarkable organs, the pituitary and the pineal 

 body, are closely associated in their genetic relations with the cere- 

 brum, since the first of these bodies originates partly and the second 

 entirely as a diverticulum from the cavity of the primary inter-brain. 



THE PITUITARY BODY. 



The pituitary body, or hypophysis cerebri, consists of two 

 portions, the large anterior oral and the small posterior cerebral 

 division. These are entirely distinct both in structure and in de- 

 velopment, since tjie anterior lobe is derived as a diverticulum 

 from the primitive oral cavity, and, as such, is lined with the oral 

 ectoderm, while the posterior lobe descends as an outgrowth 



from the floor of the primary inter- 

 FlG - 351- brain, its stalk remaining as the infun- 



dibulum. 



In the embryo temporarily, and in 

 many lower vertebrates permanently, the 

 tissues composing the posterior lobe 

 assume a distinctly nervous type ; in the 

 higher animals, however, this character is 

 lost, the lobe remaining small and rudi- 

 mentary and its cavity undergoing obliter- 

 ation ; the primary nervous character of 

 section of human pituitary body: the cere bral lobe disappears as the in- 



C, portion of posterior or nervous L . 



lobe; P, portion of anterior or grOWth of the COnnCCtlVC tlSSUC and 



glandular lobe, consisting of tubular the blood-VCSSCls takes place. The TC- 

 acini (a) ; s, connective-tissue septa ; . . 



v, biood-vesseis. mains oi the immature nervous elements 



are sometimes recognized in the branched 



and spindle pigmented cells found in this part of the pituitary 

 body, as well as in the partially-preserved cavity lined with ciliated 

 columnar cells. 



