FUNCTIONS OF THE MEDULLA OBLONGATA. 279 



total destruction of the cord, by the same means, is almost instantane- 

 ously fatal. 



Functions of the Medulla Oblongata. 



In a physiological, as well as in an anatomical point of view, the 

 medulla oblongata is to be regarded as a continuation upwards of the 

 spinal cord ; but owing to the importance of the organs, the nerves of 

 which proceed from it, its functions are of greater consequence than 

 those of the cord. It is further remarkable as being the seat of the 

 decussation, or crossing from one side to the other, of the paths of the 

 voluntary motorial stimulus from the cerebrum above, to the spinal 

 cord below ; this decussation of the motor tracts occurs almost entirely 

 at the lower part of the medulla oblongata. (Brown-Se'quard.) 



The medulla oblongata acts, like the cord, as a conductor of the 

 effects of sensory impressions upwards, from the cord to the cerebrum ; 

 the paths of such sensory impressions, are probably, on grounds of 

 analogy, through the gray matter, and the continuations upwards of 

 the ascending fibres of the posterior pyramids, and not through the 

 restiform bodies, which pass up to the cerebellum. These paths do 

 not again decussate in the medulla, having already crossed over in the 

 gray matter of the cord. The medulla oblongata may, also, transfer 

 the effects of sensory impressions, from one nerve to another ; as when 

 any irritation in the stomach, acting on the vagi nerves, produces sym- 

 pathetic headache, or pains in other parts of the body. Moreover, 

 radiations of sensation may take place through the medulla oblongata, 

 as when the pain from a single decayed tootn is transferred to other 

 branches of the fifth nerve, and causes pain in the corresponding tooth 

 in the other jaw, or in various parts of the same side of the face and 

 head. 



The medulla oblongata likewise acts as the conductor of the effects 

 of the voluntary motorial stimulus passing down from the brain, on- 

 wards to the spinal cord and spinal nerves. The paths through which 

 this conduction takes place, are the fibres of the anterior pyramids, 

 division of one of which produces in an animal paralysis of one side 

 of the body (Magendie) ; whilst irritation of these is not followed by 

 indications of pain, as is the case when the restiform bodies are simply 

 touched. The fibres of the anterior pyramids decussate in so remark- 

 able and complete a manner, that the motorial stimulus, proceeding 

 down the peduncle of one cerebral hemisphere, crosses completely 

 over in the medulla, to the opposite side of the cord, at the so-called 

 decussation of the anterior pyramids. Thus, in artificial division of 

 one-half of the spinal cord of an animal, paralysis of motion occurs, 

 as already mentioned, on the same side of the body ; whilst if the sec- 

 tion be made opposite the decussation of the anterior pyramids, in the 

 medulla oblongata, paralysis of the muscles follows on both sides ; but 

 if the section be still higher, in the very highest part of the medulla 

 oblongata, the paralysis happens only on the opposite side of the 

 body. These results are confirmed by other experiments, and by ob- 

 servations, in disease, in man ; and these are of high importance, for 

 sections of the medulla oblongata itself, especially of its posterior 



