70 
ON THE SENSE OE SMELL IN DOGS. 
my uncovered head above the level of the surrounding fields. 
When she was led within two hundred yards of the place, she 
instantly perceived my odour, and ran in a straight line to where I 
had then ducked my head, so that she should receive no assistance 
from her sense of sight. This experiment shows that, in the 
absence of wind, the odour of my head (and no doubt, in a lesser 
degree, that of my body) bad diffused itself through the air in all 
directions, and in an amount sufficient to enable the setter to 
recognize it as my odour at a distance of two hundred yards. 
From the above experiments I conclude that this bitch distin- 
guishes my trail from that of all others by the peculiar smell of my 
boots (1 to 6), and not by the peculiar smell of my feet (8 to 11). 
No doubt the smell which she recognizes as belonging distinctively 
to my trail is communicated to the boots by the exudations from 
my feet ; but these exudations require to be combined with shoe- 
leather before they are recognized by her. Probably, however, 
if I had always been accustomed to shoot without boots or 
stockings, she would have learnt to associate with me a trail made 
by my bare feet. The experiments further show that although a 
few square millimetres of the surface of one boot is amply 
sufficient to make a trail which the animal can recognize as mine, 
the scent is not able to penetrate a single layer of brown paper 
(10). Purthermore, it would appear that in following a trail 
this bitch is ready at any moment to be guided by inference as 
well as perception, and that the act of inference is instantaneous 
(12 and 13 as compared with 2, 8, and 11). Lastly, the experi- 
ments show that not only the feet (as these affect the boots), but 
likewise the whole body of a man exhales a peculiar or individual 
odour, which a dog can recognize as that of his master amid a 
crowd of other persons (15) ; that the individual quality of this 
odour can be recognized at great distances to windward (15), 
or, in calm weather, at great distances in any direction (16) ; 
and that it does not admit of being overcome by the strong smell 
of aniseed (14), or by that of many other footprints (4) . 
