FUNCTIONS OF THE MEDULLA OBLONGATA. 405 



dulla, and proceed chiefly to the cerebellum, but that small 

 part behind, called posterior pyramid, is continued on with the 

 fasciculus teres of each side along the floor of the fourth ven- 

 tricle to the cerebrum. 



As in structure, so also in the general endowments of their 

 several parts, there is, probably, the closest analogy between 

 the medulla oblongata and the spinal cord. The difference 

 between them in size and form appears due, chiefly, first, to 

 the divergence, enlargement, and decussation of the several 

 columns, as they pass to be connected with the cerebellum or 

 the cerebrum; and, secondly, to the insertion of new quantities 

 of gray matter in the olivary bodies and other parts, in adap- 

 tation to the higher office and wider range of influence which 

 the medulla oblongata as a nervous centre exercises. 



Functions of the Medulla Oblongata. 



In its functions the medulla oblongata differs from the 

 spinal cord chiefly in the importance and extent of the actions 

 that it governs. Like the cord, it may be regarded, first, as 

 conducting impressions, in which office it has a wider extent 

 of function than any other part of the nervous system, since 

 it is obvious that all impressions passing to and fro between 

 the brain and the spinal cord and all nerves arising below the 

 pons, must be transmitted through it. The decussation of part 

 of the fibres of the anterior pyramids of the medulla oblongata 

 explains the phenomena of cross-paralysis, as it is termed, i. e., 

 of the loss of motion in cerebral apoplexy, being always on the 

 side opposite to that on which the effusion of blood has taken 

 place. Looking only to the anatomy of the medulla oblongata, 

 it was not possible to explain why the loss of sensation also is 

 on the side opposite the injury or disease of the brain ; for 

 there is no evidence of a decussation of posterior fibres like 

 that which ensues among the anterior fibres of the medulla 

 oblongata. But the discoveries of Brown-SSquard have shown 

 that the crossing of sensitive impressions occurs in the spinal 

 cord (see p. 393). 



The functions of the medulla oblongata as a nerve-centre 

 seem to be more immediately important to the maintenance of 

 life than those of any other part of the nervous system, since 

 from it alone, or in chief measure, appears to be reflected the 

 nervous force necessary for the performance of respiration and 

 deglutition. It has been proved by repeated experiments on 

 the lower animals that the entire brain may be gradually cut 

 away in successive pprtions, and yet life may continue for a 

 considerable time, ancj the respiratory movements be uninter- 



