SULCI OR FISSURES OF THE CEREBELLUM. 573 



face, from which it seems to derive no fibres. The arrange- 

 ment of the cineritious substance of the medulla oblongata, is 

 seen in fig. 220, e, page 560. 



It will thus be seen that the medulla oblongata, is very com- 

 plicated and intricate in its interior structure. It has been 

 variously described by different anatomists, and its structure is 

 not yet probably thoroughly understood. Its anterior or motorial 

 fibres appear evidently directed upwards towards the cere- 

 brum ; its posterior or sensiferous pass backwards and out- 

 wards as the corpus resiforme, (inferior peduncle of the 

 cerebellum) to the centre of the cerebellum, where it meets 

 with a cineritious mass, called the corpus dentatum. From 

 this point its fibres are radiated in increased numbers, to the 

 circumference of the cerebellum, from whence, they have been 

 considered by Foville as again reflected inward, returning nearly 

 upon the same course to be converged into the crus cerebelli 

 of each side, and continued onward to form a part of the 

 structure of the pons. 



Of the Cerebellum. 



The cerebellum lies below the posterior lobe of the cerebrum, 

 in a cavity inclosed, below and behind by the sphenoid and 

 occipital bones, laterally by the petrous portions of the tem- 

 poral bones, and above by the tentorium. It measures trans- 

 versely at its greatest breadth, from three inches ten lines, to 

 four inches ; longitudinally in the centre, twenty lines ; either 

 lateral portion is about two inches long, and about sixteen lines 

 thick at its middle. The lateral parts are called hemispheres. 

 The central portion, from being the first part of the organ de- 

 veloped in the inferior animals and in the human foetus, is 

 called the fundamental portion by Gall and Spurzheim.* It 

 consists of two portions, the inferior and superior vermiform 

 processes, so named from the transverse ridges upon the sur- 

 face, which give them the appearance of a worm. The anterior 



* Reil considered this central part, a general commissure, but this is evi- 

 dently an error, for we find this part sometimes, constituting the whole cerebel- 

 lum, as in rabbits, where there are no lateral lobes to connect. 



