GRAY SUBSTANCE OF THE MEDULLA OBLONGATA. 



CHAPTERII. 



MOKPHOLOGIOAL CHANGES IN THE MEDULLA OBLONGATA OF MAN. 



(1.) In the region of the first cervical nerve the general form of the human 

 medulla has been very well represented by Stilling^ and by Clarke.^ The general 

 plan is similar to that observed in the sheep, with slight differences, chiefly due to 

 the nearly circular form of the human medulla^ as compared with the more elongated 

 or elliptical form in most of the mammalia, producing a greater concentration of 

 parts, especially in the lower regions, where the contrast is very decided. The 

 restiforin and post-pyramidal nuclei are developed earlier and are much larger in 

 man and the carnivora than in the lower mammalia, and a few other differences 

 occur higher up, which wiU, be noticed presently. 



(2.) Figs. 17, 17", Plates V, and XIV, show the general arrangement of parts 

 in the vicinity of the decussation of the pyramids. By comparison with Plates I, 

 and XIII, Figs. 1, 1", it wiU be seen that the principal differences consist in a more 

 complete separation of the cervix (d) and caput (6), and in the much greater devel- 

 opment of the restiform (r, r) and post-pyramidal {p, p) nuclei, which are already 

 very prominent and contain very many cells. The post-pyramidal nuclei have 

 expanded backwards into a fan-Uke network of cells and fibres, nearly fiUing the 

 post-pyramidal bodies on each side of the posterior fissure. The cells of the resti- 

 form nucleus are scattered throughout the posterior portion of the cervix, but are 

 mostly concentrated along its outer border, lateral as well as posterior ; they are 

 large and easily distinguishable, even with a low power. The cells of the tractus 

 intermedio-lateralis (t) are still persistent along the outer border of the gray sub- 

 stance, between the anterior and posterior cornua, but are mostly pushed inwards 

 towards the central canal, behind and on each side of which soon appears a large 

 group of cells, constituting the nucleus of the spinal accessory. The caput cornu 

 (b) contains a few scattered cells, as also does the network extending across to 

 the anterior cornu, which latter contains very numerous large multipolar cells. 



The large wings formed by the tractus intermedio-lateralis (t), are here plainly 

 seen ; they have been called by Eeichert' the lateral cornua (seitliche Strange oder 

 Horner). A little higher up, the anterior cornua are stiU further contracted, and 

 the first indications are seen of the olivary columns and of the antero-lateral nuclei. 



* Medulla Oblongata, pi. iv, fig. L 



" Philos. Transactions, 1858, pi. xiv, fig. 23 ; pi. xv, fig. 19. 



= Bail des Menschlichen Gehirns. II. Leipzig, 1861. 



