HUMAN AND MAMMALIAN. 



scattered ; no distinct roots can be traced to the surface. The vagus nucleus still 

 contains numerous cells, mostly crowded back from the apex. The nucleus has 

 been pushed forwards so that its base no longer lies on the floor of the fourth ven- 

 tricle, but is separated from it by a commissure of fibres and cells connecting the 

 hypoglossal nucleus with that of the auditory. 



The auditory nucleus {A) is now quite large, pyramidal in form, and has already 

 absorbed the outer portion of the vagus nucleus as well as the post-pyramidal body. 

 It is bordered along its outer edge by a network of fibres, inclosing large and numer- 

 ous longitudinal fasciculi, forming a very conspicuous fringe, which still higher up 

 is more distinctly separated from the inner portion, forming a very complete border, 

 called by Clarke the '■^ outer nucleus." Both portions of the auditory nucleus con- 

 taia numerous cells of medium size, obovate and stellate. 



The restiform body is still crowded with cells, and at its outer edge gives off fringes 

 of fibres reaching into the dark border of longitudinal fibres by which it is now 

 bounded (Jc), the band of external arciform fibres (a) being pushed further for- 

 wards, and thinned off posteriorly more and more, to make way for the posterior 

 and anterior divisions of the auditory roots, which presently make their appearance. 



The caput is penetrated by the vagus roots and studded with small cells, particu- 

 larly near the apex of the vagus nucleus. It is also connected with the restiform 

 body, and with the point of the auditory nucleus, by a network of ceUs and fibres, 

 and anteriorly with the remains of the antero-lateral nucleus. 



The small cells of the olivary bodies have mostly disappeared, except in the 

 immediate vicinity of the raphe. Some ceUs are still persistent in the locality of the 

 antero-lateral nucleus, while further back and close to the caput a large group is 

 seen, the commencement of a column which steadily increases as we ascend, its some- 

 what large cells being finally grouped together as the upper olivary bodies (Plates 

 XIII, XIV, 0'). In (Fig. 7") these cells as well as the remains of the antero- 

 lateral nucleus appear to be comiected with the posterior portion of the hypoglossal 

 nucleus by radiating fibres. 



(7.) StiU higher up the principal changes consist in the gradual pushing forwards 

 of the vagus nucleus, which, as it is pushed towards the apex of the great triangular 

 mass formed by the fusion of the vagal, hypoglossal, and auditory nuclei, becomes 

 the nucleus of the glosso-pharyngeal. These changes have been well figured by 

 StiUmg {Textur und Function der Medidla Oblongata. Erlangen, 1843, Taf. vii, 

 Figs. 1 — 6). The roots of the glosso-pharyngeal subdivide into many bundles in 

 their course through the caput ; some seem to pass into the auditory nucleus, some 

 into their ovm proper nucleus, whilst some, especially in higher sections, reach for- 

 wards as far as the remains of the hypoglossal nucleus. 



The restiform body is still further reduced in size by the dark border of longitudi- 

 nal and oblique fibres by which it is surrounded, which has now attained very con- 

 siderable breadth. The olivary bodies have entirely disappeared, with the excep- 

 tion of a few quite large cells which still linger about the raphe near the olivary 

 commissure. 



