ON THE MAMMALIAN NERVOUS SYSTEM. 



507 



The trunk of the last dorsal nerve was then excited. 



Cat 378. Cord divided between 8th and 9th dorsal vertebrae, and at disc between 

 3rd and 4th lumbar vertebrae. 



Excitation of left 13th dorsal nerve, effect in lower (lumbar) portion of cord. 



In order to see whether this effect was transmitted by the fibres in the posterior 

 or lateral column, the left posterior column was now divided opposite the centre of 

 the body of the 1st lumbar vertebra. The excitation of the root now gave the 

 following effect : 



We here see most unmistakably that the descending effect is very different in 

 character and localisation from the ascending effect previously described, for (l) it is 

 much smaller, (2) it is mainly dependent upon the continuity of the posterior column, 

 whereas the ascending indirect effect is dependent upon the integrity of the lateral 

 column. 



These results, which were quite unexpected by us, are in very remarkable 

 agreement with the anatomical researches of GOLGI, &c. 



SECTION 6.- ON THE ELECTEICAL CHANGES IN THE CORTICAL NERVE CENTRES. 



In all the preceding investigations we have studied the characteristics of a nerve 

 centre by examining the electrical changes, and thus the excitatory processes present 

 in the nerve fibres connected with such a centre. We chose the spinal cord since it 

 contains the simplest form of a complete centre that the Mammalian nervous system 

 presents. 



3 T 2 



