488 THE BRAIN 



The velum cannot be properly seen at present, but it will be exposed at 

 a later stage of the dissection. 



Lobus Uvulse. The uvula is a triangular elevation placed between the 

 two tonsils. It is connected, across the sulcus valleculee, with each tonsil 

 by a low-lying ridge of grey matter which is scored by a few shallow 

 furrows, and in consequence termed \hz furrowed band. The two tonsils 

 and the uvula form the lobus uvula. 



To see the furrowed band it will be necessary to remove the tonsil on 

 one side, when the posterior medullary velum also will be exposed. 



Lobus Pyramidis. The pyramid is connected with the biventral 

 lobule on each side by a faint ridge which crosses the sulcus vallecul<K. 

 The term lobus pyramidis is given to the three lobules which are thus 

 associated with each other. 



Lobus Tuberis. The tuber vermis, which forms the most posterior part 

 of the inferior vermis, is composed of several folia, which run directly into the 

 inferior semilunar lobule on each side. The three parts of the lobus tuberis 

 are thus linked together. The inferior semilunar lobule is traversed by 

 two, or it may be three, curved fissures. The most anterior of these cuts 

 off a narrow, curved strip of cerebellar surface called the lobulus gracilis. 



Dissection. A median section should now be made through 

 the vermis of the cerebellum and the two medullary vela into 

 the cavity of the fourth ventricle. When the two parts of the 

 cerebellum are drawn slightly asunder, a view of the fourth 

 ventiicle is obtained ; further, the connections of the two 

 medullary vela and the arrangement of the peduncles of the 

 cerebellum can be more clearly understood. 



Arbor Vitse Cerebelli. The cut surface of the cerebellum 

 presents a very characteristic appearance. The grey matter 

 on the surface stands out distinctly from the white matter in 

 the interior. Further, the complete manner in which the 

 surface is cut up by the sulci into secondary and tertiary folia 

 is seen. The central mass of white matter in the vermis is 

 termed the corpus medullare. From the corpus medullare, 

 prolongations pass into the various lobules, and they give off 

 branches to supply each folium with a central white stem or 

 core. The term arbor vita is applied to the appearance 

 which consequently results when a section is made through 

 the cerebellum (Fig. 198). 



Cerebellar Peduncles. The cerebellar peduncles are the 

 structures which connect the cerebellum with the medulla 

 oblongata, the pons and the mid-brain. They are three in 

 number on each side viz., the inferior, the middle, and 

 the superior. They are all directly connected with the white 

 medullary centre of the cerebellum, and are composed of 

 fibres which emerge from or enter the white central sub- 

 stance of the organ. 



The middle peduncle or brachium pontis is much the 



