MEDULLA OBLONGATA. 115 



The Medulla Oblongata is within the cranium, lying 

 upon the cuneiform process of the occipital bone, has the 

 same arrangement of the white and gray matter as the 

 spinal marrow, and by Mr. Salandier is regarded as the 

 foundation of the central organs. It is composed of six 

 eminences, the corpora pyramidalia, the corpora olivaria, 

 and -the corpora restiformia which are nothing more than 

 the enlargements of the nervous tracts belonging to the 

 spinal marrow. 



The corpora pyramidalia correspond to the motor tract; 

 the corpora olivaria to the respiratory, and the corpora 

 restiformia to the sensory. From the corpora pyramidalia 

 nervous filaments can be traced through the pons varolii, 

 crura cerebri, thalami, corpora striata, and thence ex- 

 panding to form part of the cerebrum. Some of these 

 filaments decussate low down, those on the right going to 

 the left side of the brain, and those on the left to the 

 right by which disposition, paralysis on the opposite side 

 of the body from injury of the head is explained. 



The corpora olivaria are by Mr. Solly regarded as chiefly 

 motor, and fibres can be traced from them through the 

 pons to the tubercula quadrigemina, or optic ganglia, and 

 thence along with the fibres of the corpora pyramidalia to 

 the cerebrum, some also going to the cerebellum. Hence 

 the cerebrum is by Gall and Spurzheim, who take this as 

 their starting point, said to be formed or developed from 

 the corpora pyamidalia and olivaria while the remain- 

 ing tract, the corpus restiforme, is as clearly traced into 

 the cerebellum. 



The corpus restiforme differs from the others, according 

 to the dissections of Mr. Solly, in having its fibres inter- 

 lacing instead of parallel. 



Most of the cranial nerves arise from the Medulla Ob- 

 longata; and from this fundamental point as a centre, the 

 primitive filaments have been traced, radiating to the cir- 

 cumference of the cerebrum and the cerebellum these 

 are called diverging fibres. Another set is traced from the 

 circumference back to the centre these are the converging 



