CHAP. X.] THE MEDULLA OBLONGATA. 267 



Hence the olivary eminences are peculiar to the human subject, 

 and some of the monkeys. 



On tracing the olivary bodies downwards, they are found to 

 approximate towards each other, the anterior pyramids which sepa- 

 rate them gradually diminishing in breadth, and they apparently 

 terminate by becoming continuous with the antero-lateral columns 

 of the spinal cord. 



The olivary bodies, though separated from the margin of the 

 pons Varolii by a distinct depression, may be traced upwards 

 through the mesocephale along with the central substance of the ' 

 medulla oblongata (fasciculi innominati of Cruveilhier), forming a 

 considerable portion of the superior layer of each crus cerebri, and 

 apparently becoming continuous with the optic thalamus and quad- 

 rigeminal bodies. 



The olivary bodies and the central substance of the medulla 

 oblongata may be described as connecting the spinal cord with the 

 quadrigeminal bodies and the optic thalami. 



It seems highly probable, that the olivary bodies constitute the 

 essential portion or nucleus of the medulla oblongata; that on 

 which its power as an independent centre depends. Strong support 

 to this view is derived from the important fact, that these bodies 

 and the central portion of the medulla oblongata, with which they 

 are directly continuous, contain that intermixture of vesicular and 

 fibrous matter which constitutes the main character of a nervous 

 centre. 



If this be correct, the anterior and posterior pyramids, and the 

 restiform bodies, must be regarded as consisting chiefly of fibres 

 which pass from the spinal cord to the cerebrum, or cerebellum, 

 and not essentially concerned in the formation of the medulla 

 oblongata. The fibres of these bodies are in fact mainly commis- 

 sural ; the anterior pyramids serving to connect the cerebral hemi- 

 spheres to the spinal cord, the restiform bodies connecting the 

 cerebellum to it, and the posterior pyramids being the means of 

 connexion posteriorly between the medulla oblongata and the cer- 

 vical and dorsal regions of the spinal cord. But the olivary bodies 

 and the central matter of the medulla are directly continuous with 

 certain principal gangliform masses of the brain, the optic thalami 

 and quadrigeminal bodies, and by their prolongation upwards form 

 a large portion of the crura of the brain. 



From the description of the minute structure of the medulla 

 oblongata by Stilling, founded upon investigations conducted in 

 the same way as those on the spinal cord, it would appear that 



