266 



INNERVATION. 



[CHAP. x. 



The restiform bodies form the lateral 

 i and posterior part of the medulla ob- 



longata. They are cylindrical in form. 

 I a Below they are distinctly continuous 



with the antero-lateral and posterior 

 columns of the cord. As they ascend, 

 they diverge and leave a considerable 

 space between them, which is the fourth 

 ventricle. Each restiform body passes 

 into the corresponding hemisphere of 

 the cerebellum, forming a considerable 

 portion of the crus, the stalk of fibrous 

 matter around which the hemisphere is 

 formed. These bodies are, therefore, 

 the bond of connexion between the 

 cerebellum and the spinal cord, for 



Posterior view of the medulla oblon- 1-1 .-i i r 



gata -.-pp. Posterior pyramids, separated which reason they have been appro- 



by the posterior fissure, rr. Restiform , i j j z. 77- 

 bodies, composed of cc, posterior columns, priately designated processus cerebelli 

 and dd. lateral part of the antero-lateral j j n ij j. 

 columns of the cord. aa. Olivary columns, tW meduUam OOlOngCltum. 



The posterior median fissure is 

 f ""' bounded on each side by a small co- 

 luinn, not exceeding one-eighth of an inch in breadth. These 

 columns are called the posterior pyramidal bodies. Their outer limit 

 and line of demarcation from the restiform bodies is indicated by 

 a superficial groove, along which a separation of the two struc- 

 tures readily takes place, in a preparation previously hardened in 

 spirit. 



The olivary bodies are oval projections on each side of the ante- 

 rior pyramids. When the latter have been carefully removed, it 

 may be demonstrated that these bodies are continuous with the 

 central part of the medulla oblongata. They are coated on the 

 outside with fibrous matter, within which is a folded lamella or 

 capsule of vesicular substance, enclosing a white nucleus. By 

 slicing off a layer of this body even with the surface of the medulla, 

 the capsule may be seen disposed as a wavy line, surrounding an 

 oval space of white matter. If examined in transverse section, 

 this wavy line of vesicular matter is still apparent, but it is incom- 

 plete behind and within; and the same may be observed on a 

 vertical section of the olivary body. This lamina is called the 

 corpus dentatum. 



When the pyramids are very largely developed, these oval pro- 

 jections on the surface of the medulla oblongata do not appear. 



