152 NOTICES OF THE MEETINGS [March 12, 
the nervous system.* And as we have seen that the emotions may 
act directly upon the muscular system through the motor nerves, 
there is no a priori difficulty in believing that Ideas may become the 
sources of muscular movement, independently either of volitions or 
of emotions.— The relations of these different modes of action of the 
nervous system, and the place which this ideo-motor form of ‘ reflex ’ 
operation will hold in regard to the rest, will be made more apparent 
by the following tabular arrangement. 
——>THE WILL —> Volitional Movement 
Intellectual processes 
f 
Emotions Crresrum——>Motor Impulse 
i) 4 
= 
Ideas y 3 3 
55 
o & 
Zs 
- = ic} 
Sensations —_——_--> Srnsory GancLiAs— Motor impulse gS 
5 
2 
f 
Impressions ———_-> § pina Conp-———>Motor impulse 
Now if that ordinary upward course of external impressions, — 
whereby they successively produce sensations, ideas, emotions, and 
intellectual processes, the will giving the final decision upon the 
action to which they prompt, —be anywhere interrupted, the im- 
pression will then exert its power in a transverse direction, and a 
‘reflex’ action will be the result. This is well seen in cases of 
injury to the Spinal Cord, which disconnects its lower portion from 
the sensorium without destroying its own power; for impressions 
made upon the lower extremities then excite violent reflex actions, to 
which there would have been no tendency if the current of nervous 
force could have passed upwards to the Cerebrum. So, if sensations 
be prevented by the state of the Cerebrum from calling forth ideas 
through its instrumentality, they may react upon the motor apparatus 
in a manner which they would never do in its state of complete 
functional activity. This the Lecturer maintained to be the true 
account of the mode, in which the locomotive movements are main- 
tained and guided in states of profound abstraction, when the whole 
attention of the individual is so completely concentrated upon his 
* To Dr. Laycock is due the credit of first extending the doctrine of reflex 
action to the Brain. 
