NERVOUS SYSTEM. 325 



Foramina Cccca. — Above and below the tuber, centiically si- 

 tuated, are little round depressions or blind holes, which are ge- 

 nerally described as the foramina cceca, superior et inferior. They 

 serve as places of lodgment for small plexuses of bloodvessels. 



Still higher than the tuber is placed the 



Medulla Oblongata"^ , 



The smallest division of the cerebral mass : more properly 

 speaking, it is the commencement of the spinal marrow^ It rests 

 upon the cuneiform process of the occipital bone, and is continued 

 upward and backward to the foramen magnum. Regarded in an 

 excised or separate state, it is of an oblong, quadrilateral figure. 

 It has a deep fissure along its middle (in which runs the basilar 

 artery) that divides it into lateral portions. Contiguous to this 

 fissure, rising from the sides of it, are two longitudinal emi- 

 nences, called the Eminenticc pyramidales. From the lateral 

 parts project two other eminences, named the Uminentia Olivares. 

 The upper surface of the medulla oblongata forms, with the tuber 

 annulare, the floor of the fourth ventricle. Though, like the 

 tuber, it is composed internally of a mixture of cortical and 

 medullary substances, its shade is lighter than that body. 



Lastly, remains to be considered the 



Pituitary Gland, 

 A reddish body, of an ovoid form, seated upon the sella tursica, 

 within a fold of the dura mater. It has a membranous capsule, 

 surrounded by cellular adhesions, by which it is firmly retained 

 in its place ; whence it is not dislodged, even though the cerebral 

 mass be taken out. It has the appearance of being highly vas- 

 cular; it is, however, of a lighter colour internally than exter- 

 nally, and assumes, in places, a mottled aspect. The ancients 

 entertained a notion that it imbibed some fluid from the brain, 

 vvhich they called pituita, through the infundibulum, and trans- 

 mitted it to the nose; but we find that these parts have no 

 communication whatever : in short, its real use is unknown. 



OF THE SPINAL MARROWf. 



The medulla spinalis, or spinal marrow, is that extended 

 cylinder of brain-like substance which is continued from the 



* " The seat of power which controls the respiratory motions is the me- 

 dulla oblongata." — " He who holds the medulla oblongata in his hand, has 

 the key to the nervous system." — C. Bell, F.R.S. 



f " In animals which do not breathe by an uniform and general motion 

 of their bodies, there is no spinal marrow, but only a long compound and 

 ganglionic nerve, extending through the body for the purpose of sensation 

 and motion. This chord in those creatures does not actuate the animal 

 machine with alternate dilatation and contraction." — The Nercous Systein. 

 By Charles Bell, F.R.S. 



