Physiology : a manual for students and practitioners . organs is dependent for regulation upon the connec-tion of the sympathetic nerves with the spinal cord. THE MEDULLA OBLONGATA. Describe, roughly, the medulla oblongata. It is a column of white and gray nerve-substance, and is an en-8—Phy. 114 NERVOUS SYSTEM. larged portion of the spinal cord, connecting the brain with thecord below. The white substance is composed of the medullaryfibres connecting brain and cord, and the gray matter is arrangedvariously between the bands of white fibres. It has an anteriorand a posterior fissure, correspon
Physiology : a manual for students and practitioners . organs is dependent for regulation upon the connec-tion of the sympathetic nerves with the spinal cord. THE MEDULLA OBLONGATA. Describe, roughly, the medulla oblongata. It is a column of white and gray nerve-substance, and is an en-8—Phy. 114 NERVOUS SYSTEM. larged portion of the spinal cord, connecting the brain with thecord below. The white substance is composed of the medullaryfibres connecting brain and cord, and the gray matter is arrangedvariously between the bands of white fibres. It has an anteriorand a posterior fissure, corresponding to those of the lower portionof the cord, and the central canal of the cord here opens into thefourth ventricle. How do the columns of the cord arrange themselves in themedulla ? The medulla continues in a general way the arrangement of thefibres in tracts of the cord below, but as the diameter is greater thegeneral shape is pyriform and the shape of the columns nearly pyra-midal (Fig. 31). The anterior columns of the cord become the Fig. Medulla Oblongata and Pons Varolii, anterior surface. anterior pyramids of the medulla; the posterior columns, the resti-form bodies, and the lateral columns correspond to the lateral tractof the medulla with the olivary bodies. The fibres, however, donot follow this arrangement so closely, but the columns of thfe corddistribute themselves variously in the medulla. THE MEDULLA OBLONGATA. 115 How are the anterior pyramids made up? TIk anterior enluiiiiis of tlu cord jscikI their fibres (the directpyramidal tract) up into the anterior pyramids, so that they arecontinuous tracts. Other fibres from the lateral columns join thefibres of the anterior pyramids, and here cross in bundles to theopposite side. These fibres uiay be seen crossing the anteriorfissure between the pyramids by gently separating the auterior])yramids. This is known as the decusuition of the pyrmnUIs. Thefibres which cross in this way belong in the cord to the porti
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysiology, bookyear1
