ON THE MAMMALIAN NERVOUS SYSTEM. 



341 



3. Spinal cord (dorsal region). 



4. Bulbo-spinal centres. 



5. Nerve. 



6. Muscular nerve-endings. 



The combinations of these parts involved in our experiments may be grouped as 

 follows, and to each group is affixed the highest and lowest galvanometric reading 

 obtained in the case of the Cat : 



From these figures, which apply to the Cat only, it is very evident that the specific 

 element distinguishing the cortex from the white fibres of the corona radiata leading 

 away from it is the energetic discharge of its own structure, the corpuscles. Reverting 

 now to the question raised at the beginning of this section, it is plain that the 

 average amount of the effect produced by the corona radiata forms practically half, viz., 

 102, that, viz., 193, evoked by the cortex, the remainder naturally corresponding with 

 the clonic after-effect. The levelling process effected by the block in the connection 

 between the pyramidal fibres and the nerves through the corpuscles of the bulbo- 

 spinal centres is so severe as apparently to reduce the increase due to the after-effect 

 to too law an intensity to make itself felt in the galvanometer in any marked degree, 

 for it will be seen in the above table that the figures for the sciatic nerve are 

 practically equal. 



Beyond multiplication of experiments to check and control these observations, we 

 did not see that further investigation in this direction would be so profitable as 

 examining the relations and action of the bulbo-spinal centres when separated from 

 the cervical region of the spinal cord (see Chapters VIII., IX., X., XL), since the 

 phenomena of conduction in fibres are far more easily studied than those in which 

 corpuscular mechanisms are involved. 



