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154 ANIMAL INTELLIGENCE 
associations or the reverse. The mature dog has em- 
bedded in his nervous system and psychic nature a 
series of connections which, without any reasoning 
answer to warn him or the reverse, are perfectly 
indifferent. 
However, new and mysterious sounds may alarm a 
mature dog more than a puppy. 
The lower animals are more sensitive to concussions 
than man, as shown by their behaviour prior to earth- 
quakes, when there are slight oscillations of the earth, 
wholly unperceived by man, yet causing alarm to the 
domestic animals. 
I have noticed that puppies are very early stimulated 
by concussions, but regret that I have not exact ob- 
servations with fixed dates to report. 
One of the earliest indications of hearing is reflex 
movement of the ears. These are quite distinct, of 
course, from the voluntary movements often seen in 
dogs and other animals. But similar, though less 
marked, movements of the external ears may be 
observed in man also, as any one may prove by asking 
an individual to listen and determine the location of 
a tunine-fork sounded behind him. These I have for 
many years been accustomed to demonstrate to my 
classes in physiology, though I have not noticed that 
they are referred to in books. There seems to be no 
relation between the extent of the reflex and the 
voluntary movements of the ears, of which some people 
are capable. When at concerts I have sometimes ob- 
served them in great numbers and variety. 
Another matter that seems to have received scant 
attention, if I may judge from the absence of printed 
references, is the condition of the ears in puppies up 
to a certain date. At birth the external ear is turned 
back, and its internal aspect strikes one by its relatively 
undifferentiated character, and the auditory meatus is 
