NEUROLOGY 



THE ENCEPHALON OR BRAIN. 



General Considerations and Divisions. The brain, is contained within the 

 cranium, and constitutes the upper, greatly expanded part of the central nervous 



system. In its early embryonic 

 condition it consists of three hollow 

 vesicles, termed the hind-brain or 

 rhombencephalon, the mid-brain or 

 mesencephalon, and the fore-brain 

 or prosencephalon; and the parts 

 derived from each of these can 

 be recognized in the adult (Fig. 

 677). Thus in the process of de- 

 velopment the wall of the hind- 

 brain undergoes modification to 

 form the medulla oblongata, the 

 pons, and cerebellum, while its 

 cavity is expanded to form the 

 fourth ventricle. The mid-brain 



Cerebral peduncle 

 Superior peduncle 



Middle peduncle 

 Inferior peduncle 



Medulla oblongata 



FIG. 677. Scheme showing the connections of the several 

 parts of the brain. (After Schwalbe.) 



forms only a small part of the 

 adult brain; its cavity becomes 

 the cerebral aqueduct (aqueduct of 



BASAL GANGLIA 

 OF FORE-BRAIN 



CORPORA 



QUAORIGEMINA 



TT RETICULAR GANGLIONIC 

 1X< MASS WIT* CRANIA 

 NERVE NUCLEI 



CENTRAL GRAY (FLOOR OF 

 FOURTH VENTRICLE AND 

 AROUND AQUEDUCT) 



CENTRAL GRAY OF I. 

 SPINAL CORD 



FIG. 678. Schematic representation of the chief ganglionic categories (I to V). (Spitzka.) 





