564 THE SENSORIAL FUNCTIONS. 



we have been able to accomplish has been to 

 trace the impressions from the organ of sense 

 along the communicating nerve to the sen- 

 sorium : beyond this the clue is lost, and we can 

 follow the process no farther. 



The exact locality of the sensorium has been 

 eagerly sought for by physiologists in every age. 

 It would appear, from the results of the most 

 recent inquiries, that it certainly does not extend 

 to the whole mass of the brain, but has its seat 

 more especially in the lower part, or basis of 

 that organ. It differs, however, in its locality, 

 in different classes of animals. In man, and 

 the mammalia which approach the nearest to 

 him in their structure, it occupies some part of 

 the region of the medulla oblongata ; probably 

 the spot where most of the nerves of sense are 

 observed to terminate. In the lower animals it 

 is not confined to this region, but extends to the 

 upper part of the spinal marrow. As we de- 

 scend to the inferior orders of the animal king- 

 dom, we find it more and more extensively dif- 

 fused over the spinal marrow ; and in the In- 

 vertebrata the several ganglia appear to be 

 endowed with this sensorial property ; but, 

 becoming less and less concentrated in single 

 masses, the character of individuality ceases to 

 attach to the sensorial phenomena ; until, in 

 Zoophytes, we lose all traces of ganglia and of 

 nervous filaments, and every part appears to 



