HUMAN AND MAMMALIAN. 39 



CHAPTER VIII. 



THE OLIVARY BODIES OF MAMMALIA. 



The structure of the olivary bodies in the mammalia has received but little 

 attention hitherto, and their existence has been entirely denied by some authcrp. 

 Schroder van der Kolk and Clarke have given the only accurate description of the 

 structure and connections of these bodies, and the results of their observations are 

 both interesting and important. As already pointed out by both these authors, the 

 situation of the olivaries is different in most of the mammaha from their position 

 in man, lying directly behind the anterior pyramids between the raphe and hj'po- 

 glossal roots ; the latter running along the outer edge of the olivary bodies, instead 

 of passing on the inner side, as is the case in man. In the sheep, the structure of 

 the ohvary bodies is reduced to a very simple type (Plate XIII, Figs. 2", S", 4", 6'', 

 1", and the corresponding figures Plates I and II, also Fig. 5) ; in this latter figure 

 the olivary is seen to consist of a folded lamina, the convolutions of which are very 

 few in number when compared with those in the human medulla. 



The laminae are united by a transverse commissure across the raphe, similar to 

 that described in man, and contain numerous, rather small, oblong or fusiform cells, 

 measuring about ^3^^3-3- to y qVo" ^^ ^^ inch on their longest diameter. The lamina 

 is everywhere penetrated by regular, wavy bundles of fibres, between which the 

 ceUs are arranged in layers, some of the fibres being evidently continuous with 

 their processes. Just behind the pyramids, on each side of the raphe, the fibres, 

 which are mostly derived from the arciform plexus, are arranged in a very 

 regular manner, often forming beautifid, wavy bands which sAveep through the 

 olivary bodies, and cross at the raphe. In Figs. 6, 6, 6" is seen the greatest 

 development of the olivaries Avhich is attained in the sheep, and even here the 

 convoluted appearance is very slight, consisting only of three or four foldings, 

 which are very much larger in proportion to the whole size of the olivary bod)' 

 than in the human medulla; while lower down (Figs. 2'', 3") no indication of folding 

 is visible, the cells being arranged in layers between bundles of arciform fibres. 

 The form of the olivary body in the sheep, and the course of the arciform fibres as 

 they pass through it, has been very well drawn by Clarke {Philos. Trans. 1858. 

 Plate XV, Fig. 26). 



The simple plan of structure of the olivary body in the sheep is well seen in 

 longitudinal sections, where it appears to be inserted or thrust like a wedge 

 between the external and internal bundles of longitudinal fibres which diverge very 

 sharply at the point where the olivary first makes its appearance, the external 

 bundles running in front along the curved surface of the meduUa, while the internal 



