ANATOMY AND PHYSIOLOGY OF THE BRAIN. 421 



performs functions in the highest degree important to 

 animal existence. It presides especially over the two func- 

 tions of deglutition and respiration, and accordingly its 

 removal leads to a sudden cessation of breathing and almost 

 instant death. 



The component parts of this organ would seem, as re- 

 gards sensibility, to have some relation to the correspond- 

 ing parts of the spinal cord. Thus, Longet found that 

 irritation of the anterior pyramids seemed painless, whilst 

 the slightest touch of the restiform bodies led to acute 

 suffering. In addition, the anterior pyramids are the sole 

 conductors of motor power, in proof of which Magendie 

 observed, after section of one of these, a complete absence 

 of voluntary movement on one half of the body, the sensi- 

 bility meanwhile remaining unimpaired. The fibres of the 

 anterior pyramids, moreover, cross over from one side to 

 the other in the median line a fact explanatory of those 

 cases of transverse paralysis in which, from injury of one 

 side of the pons or ganglia of the brain, paralysis of volun- 

 tary movement ensues on the opposite side of the body. 

 Motor nervous force, accordingly, from the two sides of the 

 brain, decussates in the oblong medulla, as we have already 

 seen that sensory impressions do in the whole course of the 

 spinal cord. The crucial transmission of impressions to 

 and frorp. the brain is best illustrated in some cases of dis- 

 ease. Several cases are on record of paralysis of one side 

 of the body co-existing with atrophy of the opposite side of 

 the brain (Van der Kolk) ; and every one conversant with 

 sheep is aware of the imperfect control over one half of the 

 body, when the opposite half of the brain contains a large 

 hydatid. 



The vital importance of the oblong medulla depends 

 chiefly on the functions it performs as the centre of the 



