sight of all familiar landmarks. During the journey one cage, 
which was suspended on a wire, was rotated hundreds of times at 
every point where the direction of the route was changed, while 
the other cage, containing control pigeons, was borne with great 
care in order to introduce as little confusion in the stimuli received 
by the semi-circular canals as possible. When released at the 
journey’s end one at a time so that they could receive no aid from 
seeing each other, Exner found that, out of the entire number, the 
first pigeon to arrive home was one that had been whirled! In 
further experiments Exner produced galvanic dizziness in half of 
his pigeons during the outward journey by means of a portable 
dry battery with which he repeatedly sent a slight galvanic shock 
through the ears. This operation causes a dizziness which is re¬ 
ferable to a failure In the semi-circular canals properly to func¬ 
tion. Thus in the case of his “galvanized” pigeons the semi-cir¬ 
cular canals had been unable to make records with any complete¬ 
ness during the outward journey but, notwithstanding the fact, 
such pigeons found their way home as quickly as the control indi¬ 
viduals which had not been so treated. ; * 
Finally, Exner narcotized pigeons in order to destroy their 
power of recording stimuli, with similar results. He accordingly 
concluded it is impossible so to confuse the sensory impressions re¬ 
ceived by a carrier pigeon upon its outward journey as to interfere 
with its ability to find its way home. Therefore, although the semi¬ 
circular canals undoubtedly assist very largely in equilibration 
and orientation as a mechanism to guide the homing pigeon they 
are inadequate and, taken alone, they certainly cannot account for 
the much more extensive journeyings of migrating birds. 
Sense of Direction Certain invcstlgators have attempted to at- 
Theory tribute to migrating birds a sixth sense, namely 
of direction, without going into embarrassing details as to what 
the physical basis of such a supposed sense might be. It has been 
repeatedly noticed that animals other than birds have an apparent 
sense of direction. Everyone can tell, either from experience or 
hearsay, the uncanny way in which a cat, tied securely in a bag 
and taken ten miles away and deserted, is found on the doorstep 
waiting to be let in when its unappreciating master returns home. 
But seriously after all the discounts rendered necessary by the ac¬ 
counts of the nature fakirs have been made, there remains in the 
behavior of animals a considerable residue of fact which seems to 
have Its only explanation in the assumption of a sense of direction. 
An instance Is given by members of the Harriman Expedition 
in Alaska of the remarkable flight of murres in a dense fog be¬ 
tween Unalaska island and their feeding ground upon another 
