294 The Older Doctrines [lect. 



experiment. " As the nature of the brain and of the nerves is 

 " one and the same, so are these alike in function. In treating 

 " of them we will so far as possible make use of experiments, nor 

 " will we at first at least go beyond the testimony of our senses." 



Experiments and the testimony of the senses teach us, he 

 says, that nerves alone feel : only those parts which possess 

 nerves feel, and they feel through their nerves. The question 

 whether tendons feel presented difficulties to him as it has 

 done to others after him ; but the main result of all his 

 experiments confirmed him in the view that nerves are the 

 only instruments of sensation, just as they by calling into 

 play the contractile power of muscles are the only instru- 

 ments of movement. 



All the nerves are gathered together into the ' medulla 

 cerebri,' into the central parts of the brain ; whence it may be 

 inferred that " this central part of the brain feels and that in it 

 " are presented to the mind the impressions which the nerves 

 " disturbed at their extreme ends have carried to the brain." 

 This conclusion is supported by the phenomena of disease and 

 by the results of experiments on living animals. Sensation 

 manifests itself by movements, and when these central parts of 

 the brain are irritated by the knife or otherwise, the movements 

 which follow abundantly prove that sensation has been excited. 

 These movements are readily seen when the corpora striata, 

 the thalamus, the crura cerebri, the pons and the medulla 

 oblongata are injured. He goes on to argue that the cortex of 

 the brain must also feel, though no movement results when 

 it is irritated. "But the medulla of the corpora striata, 

 " or of the crura, or of the pons differs in no way from that of 

 " the rest of the brain except the actual cortex, and this unless 

 "it itself felt would be unable to bestow feeling on the medulla. 

 " If indeed the medulla is one and the same, and exactly alike 

 "at the summit and at the base of the brain, and if the deeper 

 " medulla obviously feels, it cannot with any right be said that 

 " the medulla placed in the higher situation, though possessing 

 " exactly the same nature, is destitute of feeling. The nerves 

 "therefore feel and carry to the brain the impressions of ex- 

 " ternal objects. Those impressions are preserved in the brain, 



