July 2 1, 1887] 



NATURE 



273 



medium which is perfectly elastic, homogeneous, and 

 isotropic, while the rocks are far from being so, we reply 

 that we have investigated the objection, and are satisfied 

 that while it has some validity, the effect of these in- 

 equalities is not great enough to seriously impair the 

 applicability of the law, nor to vitiate greatly the results 

 to be deduced from it. The analysis we offer is a novel 

 one. We attach considerable importance to it, and 

 the consequences which flow from it are somewhat 

 remarkable. 



[To be continued.) 



I 



EXPERIMENTS ON THE SENSE OF SMELL 

 IN DOGS} 

 ONCE tried an experiment with a terrier of my own, 

 which shows, better than anything that I have ever read, 

 the almost supernatural capabilities of smell in dogs. On 

 a Bank holiday, when the Broad Walk in Regent's Park 

 was swarming with people of all kinds, walking in all 

 directions, I took my terrier (which I knew had a splendid 

 nose, and could track me for miles) along the walk, and, 

 when his attention was diverted by a strange dog, I sud- 

 denly made a number of zigzags across the Broad Walk, 

 then stood on a seat, and watched the terrier. Finding I 

 had not continued in the direction I was going when he 

 left me, he went to the place where he had last seen me, 

 and there, picking up my scent, tracked my footsteps over 

 all the zigzags I had made, until he found me. Now, in 

 order to do this, he had to distinguish my trail from at 

 least a hundred others quite as fresh, and many thousands 

 of others not so fresh, crossing it at all angles.^ 



The object of the experiments about to be described 

 was that of ascertaining whether a dog, when thus dis- 

 tinguishing his master's trail, is guided by some distinctive 

 smell attaching to his master's shoes, to any distinctive 

 smell of his master's feet, or to both -these differences 

 combined. 



I have a setter-bitch, over which I have shot for eight 

 years. Having a very good nose, she can track me over 

 immense distances, and her devotion to me being very 

 exclusive, she constituted an admirable subject for my 

 experiments. 



These consisted in allowing the bitch to be taken out 

 of the kennel by someone to whom she was indifferent, 

 who then led her to a pre-arranged spot from which the 

 tracking was to begin. Of course this spot was always to 

 leeward of the kennel, and the person who was to be 

 tracked always walked so as to keep more or less to lee- 

 ward of the starting-point. The district — park-lands sur- 

 rounding a house — was an open one, presenting, however, 

 numerous trees, shrubberies, walls, &c., behind which I 

 could hide at a distance from the starting-point, and so 

 observe the animal during the whole course of each ex- 

 periment. Sundry other precautions, which I need not 

 wait to mention, were taken in order to insure that the 

 bitch should have to depend on her sense of smell alone, 

 and the following are the experiments which were 

 tried : — 



(i) I walked the grass-lands for about a mile in my 

 ordinary shooting-boots. The instant she came to the 

 starting-point, the bitch broke away at her full speed, 

 and, faithfully following my track, overtook me in a few 

 minutes. 



(2) I set a man who was a stranger about the place 

 to walk the park. Although repeatedly put upon his 

 trail by my servant, the bitch showed no disposition to 

 follow it. 



(3) I had the bitch taken into the gun-room, where she 



' Paper read by Mr. George J. Romanes, before the Linnean Society, on 

 December i6, 1886. Reprinted from the Linnean Society's Journal — Zoology, 



vol. XX. 



' " Mental Evolution in Animals," pp. 92-93 ; where also see for additional 

 lemarks of a general kind on the sense of smell in different animals. 



saw me ready to start for shooting. I then left the gun- 

 room and went to another part of the house, while my 

 gamekeeper left the house by the back door, walked a 

 certain distance to leeward in the direction of some par- 

 tridge-ground, and then concealed himself. The bitch, 

 who was now howling to follow me, was led to the back 

 door by another servant. Quickly finding the trail of the 

 gamekeeper, she tracked it for a few yards ; but, finding 

 that I had not been with him, she left his trail, and hunted 

 about in all directions for mine, which, of course, was no- 

 where to be found. 



(4) I collected all the men about the place, and directed 

 them to walk close behind one another in Indian file, 

 each man taking care to place his feet in the footprints of 

 his predecessor. In this procession, numbering twelve 

 in all, I took the lead, while the gamekeeper brought up 

 the rear. When we had walked two hundred yards, I 

 turned to the right, followed by five of the men ; and at 

 the point where I had turned to the right, the seventh 

 man turned to the left, followed by all the remainder. 

 The two parties thus formed, after having walked in 

 opposite directions for a considerable distance, concealed 

 themselves, and the bitch was put upon the common 

 track of the whole party before the point of divergence. 

 Following this common track with rapidity, she at first 

 overshot the point of divergence ; but, quickly recovering 

 it, without any hesitation chose the track which turned to 

 the right. Yet in this case my footprints in the common 

 track were overlaid by eleven others, and in the track to 

 the right by five others. Moreover, as it was the game- 

 keeper who brought up the rear, and as in the absence of 

 my trail she would always follow his, the fact of his scent 

 being, so to speak, uppermost in the series, was shown in 

 no way to disconcert the animal \yhen following another 

 familiar scent lowermost in the series. 



(5) I requested the stranger before mentioned to wear 

 my shooting-boots, and in them to walk the park to lee- 

 ward of the kennel. When the bitch was led to this trail, 

 she followed it with the eagerness wherewith she always 

 followed mine. 



(6) I wore this stranger's boots, and walked the park as 

 he had done. On being taken to this trail, the bitch could 

 not be induced to follow it. 



(7) The stranger walked the park in bare feet ; the 

 bitch would not follow the trail. 



(8) I walked the park in bare feet : the bitch followed 

 my trail ; but in quite a different manner from that which 

 she displayed when following the trail of my shooting- 

 boots. She was so much less eager, and therefore so 

 much less rapid, that her manner was suggestive of great 

 uncertainty whether or not she was on my track. 



(9) I walked the park in new shooting-boots, which had 

 never been worn by anyone. The bitch wholly refused 

 to take this trail. 



(10) I walked the park in my old shooting-boots, but 

 having one layer of brown paper glued to their soles and 

 sides.° The bitch was led along my track, but paid no 

 attention to it till she came to a place where, as I had 

 previously observed, a small portion of the brown paper 

 first became worn away at one of my heels. Here she 

 immediately recognized my trail, and speedily followed it 

 up, although the surface of shoe-leather which touched 

 the ground was not more than a few square millimetres. 



(11) I walked in my stocking-soles, trying first with 

 new cotton socks. The bitch lazily followed the trail a 

 short distance and then gave it up. I next tried woollen 

 socks which I had worn all day, but the result was the 

 same, and therefore quite different from that yielded by 

 my shooting-boots, while more resembling that which was 

 yielded by my bare feet. 



(12) I began to walk in my ordinary shooting-boots, 

 and when 1 had gone fifty yards, I kicked them off and 

 carried them with me, while I continued to walk another 

 three hundred yards in my stocking-soles ; then I took off 



