350 NERVOUS SYSTEM. 



front of the Medulla Spinalis. The fissure is two or three lines 

 deep, which is rendered manifest by removing the pia mater. 

 The Corpora Pyramidalia are placed one on either side of it, 

 and are oblong bodies; being a continuation of the chords that 

 decussate from the opposite sides of the spinal marrow. These 

 bodies occupy the whole length of the Medulla Oblongata, in- 

 crease in breadth as well as in elevation during their ascent, 

 and are, lastly, somewhat cpnstricted or diminished abruptly, 

 where they join the Protuberantia Annularis or Cerebralis. 

 Precisely at the latter point, between their bases, is a deep tri- 

 angular pit, into which penetrates the pia mater. J. F. Meek- 

 el says, that they are united at their lower extremities by a 

 small transverse medullary Commissure of a line and a half ir> 

 breadth. This junction is above the decussation of the chords 

 from which the Corpora Pyramidalia arise. 



The ErninentiaB Olivares are two bodies ; one on either side, 

 at the external margin of the corpus pyramidale. They are 

 about seven lines long: two and a half wide, and are elevated 

 to the height of one line. The elevation ceases somewhat short 

 of the annular protuberance, but their anterior structure is con- 

 tinued into the latter, and may be traced into the thalamus ner- 

 vi optici. 



Like the pyramidalia, those bodies are medullary externally; 

 but within, there is a nucleus of cineritious matter, called, from 

 the irregularities of its margin, Corpus Fimbriatum, and which 

 encloses some medullary matter. The corpus fimbriatum is open 

 at the inner circumference, and has the medullary matter which 

 it contains, continuous there with the substance of the corpus 

 pyramidale. Below, its circumference is continuous with the 

 cineritious matter of the medulla spinalis. In the slight depres- 

 sion between the corpus pyramidale and the eminentia olivaris, 

 are the roots of the hypoglossal nerve. 



The Corpora Restiformia, also one on either side, are placed 

 at the lateral posterior margins of the medulla oblongata, just 

 posterior to the Eminentise olivares ; and are readily brought into 

 view by elevating the contiguous parts of the cerebellum. They 

 are elliptical risings of an inch in length; their lower extremi- 

 ties are in contact, and project where they begin to arise from 

 the borders of the posterior fissure of the medulla oblongata; 



