492 THE LAWS OF ORIENTATION AMONG ANIMALS. 



Bonnier. To-day it is known that their function is directly connected 

 with the faculty of equilibration and is entirely independent of audition. 

 M. P. Bonnier, after having' studied throughout the entire animal 

 series the functions of tbe labyrinth and those organs which precede it, 

 by comparing the data of comparative anatomy and physiology and 

 verifying them by clinical observations, has been able to show that 

 these organs subserve directly what he calls the " sense of altitudes," 

 which furnishes the images of position, of distribution, and consequently 

 of movement and of displacement in space. 1 



It is not yet exactly known what is the physiological excitant which 

 puts in action the semicircular canals; awaiting further researches for 

 the settlement of this interesting point, we will try to determine the 

 method of action of the sense of direction. This way of procedure is 

 moreover in no way illogical— in natural sciences, as in others, the 

 knowledge of the effect usually precedes the knowledge of the cause. 



An animal wandering in a strange territory follows on his return 

 the reverse of the road, more or less winding, by which he came. 

 When he reaches known territory he moves in a straight line to his 

 destination. 



The carrier pigeon, set at liberty at a distance of some 500 kilometers 

 from its home, follows, in returning, the railroad which brought it; 

 it is now guided by its sixth sense. Having in this way reached the 

 known horizon, say 80 kilometers from its home, it no longer depends 

 on its sixth sense, but goes by its sight straight homeward. 



At other times when it reaches known regions the pigeon does not 

 think of making use of its five senses, but follows its former path 

 back to its cote. Sometimes it goes past it; thus we have seen 

 pigeons returning from a long* journey pass within 40 or 50 meters of 

 the cote, go on and only return after an hour or two, having covered in 

 this way, perhaps from 30 to 60 kilometers in the wrong direction. 



If a common pigeon, accustomed to using almost exclusively its five 

 senses, and a carrier pigeon broken to long voyages, are carried about 

 10 kilometers away from the cote, when they are successively released 

 an interesting fact is noticeable — the ordinary pigeon, going by sight, 

 will usually make its way much more rapidly than the carrier pigeon, 

 who will find its way back carefully with the aid of its sense of 

 direction. 



From this fact we may conclude that the sense of direction does not 

 combine its action with that of the live others. It begins to act in a 

 zone where the other senses are inactive, and often continues to act in 

 the known region to the exclusion of the other five senses. 



It seems that it is not actuated by impressions received from the 

 path followed and that it is in some degree a subjective organ. We 



1 We can only refer our readers to the researches of M. Bonnier on the Ear (Leaute 

 Collection) and to a recent report to the Biological Society on the Seuse of Orienta- 

 tion (December 11, 1897). 



