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 (a) the pyramidal fibres, () the fibres 

 from lateral tracts, sensory paths to the temporo-occipital (?) region, 

 and (i) the fibres from the pontine nuclei and the cerebellum. 



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 the 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 - 35i- 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 

 the cerebral lobe disappears as the in- 

 growth of the connective tissue and 

 the blood-vessels takes place. The re- 

 mains of 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. 



Section of human pituitary body : 

 C, portion of posterior or nervous 

 lobe ; P, portion of anterior or 

 glandular lobe, consisting of tubular 

 acini (a) s, conneciive-tissue septa ; 

 v, blood-vessels. 



