202 HEAD AND NECK. 



We know that reflex action, prompted by stimuli 

 from outside the body, acts best when it has but Uttle 

 connection with the brain. In fact, the smaller the 

 comparative size of the brain, the quicker and more 

 accurately are instinctive movements performed. Thus 

 we see animals with, comparatively, a very small brain, 

 or with none at all, get out of danger, or seize their prey, 

 with an amount of speed and precision which it would be 

 hopeless for any man to attempt to rival ; simply because 

 the action of his instinct is impeded by the influence of a 

 large brain. We find this demonstrated in ourselves, in 

 the case of movements which, like those in fencing, boxing 

 and dancing, for instance, can be executed only slowly 

 and clumsily at first, when they need the exercise of 

 thought, become capable of being performed with the 

 speed and correctness of a machine, as soon as practice 

 has made them almost automatic. 



Sir James Crichton Browne has shown that wild ducks 

 are far more intefligent than tame ones, which, since their 

 domestication, are " sinking into imbecility." In com- 

 paring twentv wild ducks with twenty tame ones, he found 

 that in the former, the proportion between the brain 

 weight and the body weight was i to 338.318 ; and in the 

 latter, i to 179.669. Hence the relative weight of the 

 brain of wild ducks is nearly twice as great as that of 

 tame ones. This is evidently a case of cessation of selec- 

 tion for many hundreds of years, and is similar to that of 

 the domestic horse, which is far less intelligent than liis 

 wild relations (Chapter XXXIII.). 



The prominent forehead (Fig. 292), to which I have 

 alluded on p. 194, indicates a large size of the intellectual 

 portion (cerebrum, p. 48) of the brain, which, on the 

 forehead is covered by only a thin plate of bone. With- 

 out wishing to import any of the jargon of phrenology 

 into a discussion on this subject, I may hazard the 

 suggestion that the portion of the brain which is con- 

 secrated to the functions of memory and perceptive power, 



