1 78 HUMAN PHYSIOLOGY 



The individual becomes a pure reflex machine even as 

 regards the cerebral arc, and each stimulus is followed 

 by an immediate reaction. The power of suggestion is 

 exaggerated. If a hypnotised person is told that he sees 

 anything he acts at once as if he did actually see it. 



5. Localisation of Functions. The question must n xt, 

 be considered whether special parts of the brain are more 

 especially connected with its three great functions 



1. The reception of stimuli. 



2. The storing of effects, and the associating of present 

 stimuli with these stored impressions. 



3. The production of the resulting actions. 



1. Reception of Stimuli. In investigating the existence of 

 special mechanisms, for this purpose, two methods of inquiry 

 are available. 



1st. By removing or stimulating parts of the brain in the 

 lower animals and studying the results. 



2nd. By observations during life on the sensations or 

 absence of sensation in patients suffering from disease of 

 the brain, and the determination of the seat of the lesion 

 after death. 



1st. Sensations are the usual accompaniment of the activity 

 of the receiving mechanism. But, in the lower animals, it is 

 not possible to have a direct expression of whether sensations 

 are experienced or not, and, therefore, in determining whether 

 removal of any part of the brain has taken away the power 

 of receiving impressions, we have to depend on the absence 

 of the usual modes of response to any given stimulus. But 

 the absence of the usual response may mean, not that the 

 receiving mechanism is destroyed, but either that the react- 

 ing mechanism is out of action or that the channels of 

 conduction have been interfered with. (See Fig. 97.) 



Thus, if light be flashed in the eye of a monkey, it re- 

 sponds by glancing towards the source of illumination : and 

 if these movements are absent this may be due to loss of the 

 receiving mechanism, to loss of the mechanism causing the 

 movements, or to interruption of the channels between these. 



