1892.] Brain Centres. 741 
Reason, on the other hand, is often engaged in holding such 
reflexes in check. Deliberation, hesitation, doubt, antagonize 
instinct in many ways, and the reasoning processes being the 
later acquired by all animals are the first to be weakened by 
age or debility. There can be no such definiteness about the 
nerve tissues engaged in reasoning processes as in instinctively, 
automatically performed acts. 
An instinct may have its impetus in a brain centre that 
controls the motions of any particular group of muscles, there- 
fore there can be no special seat for instinct in general but as 
many different seats as there are brain areas concerned in 
coordinating the multitude of muscular acts. Reason involves 
every sense and sometimes controls all voluntary motions, 
hence its seat cannot be special, and, its operations being 
general, so must be its functionating mechanism. Further- 
more, the more recently formed and less definitely constructed 
fasiculi and nerve cells are apparently more engaged in reason- 
ing processes than the more. fully elaborated and perfected 
strands for simpler reflex acts, such as are concerned in 
instinctively performed motions. 
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