NEUROLOGY 





Hind-brain or 

 Rhombencephalon 



1. Myelencephalon 



2. Metencephalon 



Isthmus rhomb- 

 encephali 



3 given in 







the corpora striata and thalami; later the fibers from the cells of the cortex are 

 added. Medullation of these fibers begins about the time of birth and continues 

 until puberty. A summary of the parts derived from the brain vesicles is given in 

 the following table : 



Medulla oblongata 

 Lower part of fourth 



ventricle. 

 Pons 



Cerebellum 

 Intermediate part of fourth 



ventricle. 



Anterior medullary velum 

 Brachia conjunctiva 



cerebelli. 



Upper part of fourth 

 ventricle. 



(Cerebral peduncles 

 Lamina quadrigemina 

 Cerebral aqueduct. 



r Thalamus 

 Metathalamus 

 Epithalamus 

 Pars mamillaris hypo- 



thalami 

 Posterior part of third 



ventricle. 

 Anterior part of third 



ventricle 

 Pars optica hypo- 



thalami 



Cerebral hemispheres 

 Lateral ventricles 

 Interventricular foramen. 



Fore-brain or 

 Prosencephalon 



1. Diencephalon 



2. Telencephalon 



The Cranial Nerves. With the exception of the olfactory, optic, and acoustic 

 nerves, which will be especially, considered, the cranial nerves are developed in a 



similar manner to the spinal nerves 

 (see page 735). The sensory or 

 afferent nerves are derived from 

 the cells of the ganglion rudiments 

 of the neural crest. The central 

 processes of these cells grow into 

 the brain and form the roots of the 

 nerves, while the peripheral pro- 

 cesses extend outward and consti- 

 tute their fibers of distribution 

 (Fig. 645). It has been seen, in 

 considering the development of the 

 medulla oblongata (page 739), that 

 the tractus solitarius (Fig. 660), de- 

 rived from the fibers which grow 

 inward from the ganglion rudiments 

 of the glossopharyngeal and vagus 

 nerves, is the homologue of the 



, , ,. , i j i i i i 



oval bundle in the cord which had 



Roof-plate 



Alar lamina 



Furrow between 

 alar and basal 

 la?nince 



Basal lamina 



Vagus nerve 



Floor-plate 



Fio. 659. Transverse section of medulla oblongata of 



human embryo, x 32. (Koiimann ) 



