286 Messrs Spittal and Stevenson on the Impression made 



ing's remarks on that subject, be decided by experiment, I beg 

 to lay the following remarks, containing the conclusions which 

 my friend Mr Robert Stevenson junior, and I, from experiment 

 and observation, have come to on this topic. The common do- 

 mestic pig was the subject of our observations. 



To ascertain the impression made by the feet of these ani- 

 mals, we with some difficulty caused them to walk across a 

 board spread over with soft clay, to about three-eighths of an 

 inch in thickness, and were satisfied, on subsequent examination 

 of the marks made, that, at some places, these were bisulcated, 

 but at others, they presented, besides the bisulcated impression, 

 those of the two posterior toes ; and indeed, this was the most 

 frequent appearance. The board, in this case, was placed in a 

 horizontal position, and we could not, owing to the unruly na- 

 ture of the animals, succeed in making them walk along it while 

 in the position of an inclined plane ; but, what answered nearly 

 the same purpose, the animals were let out into a court, the sur- 

 face of which was generally uneven, hard at some places, and 

 soft at others. 



In this case, we observed, that while walking down a soft in- 

 clined surface, there were always four marks, and this was gene- 

 rally the case on soft level ground, where the yielding surface 

 was deep, so that the animal's feet sunk deeper than they could 

 have done on a shallow soft surface, thinly spread over an un- 

 yielding one ; and on places of such a nature, we frequently 

 observed bisulcated impressions, but more frequently with marks 

 of the posterior toes added to these. 



On observing the animals walking over an unyielding hori- 

 zontal surface, it was quite evident that the two posterior toes 

 generally touched the ground when the animals took long steps, 

 and it is clear that this brings the posterior toes nearer to the 

 ground, by causing the legs to form a more acute angle with it, 

 than when shorter steps are taken, — the legs in the latter case 

 forming more nearly a right angle with the ground, and rest- 

 ing entirely upon the two anterior toes, as is generally the case 

 when standing upright. They thus leave on the ground a bisul- 

 cated impression, provided the surface be not too soft, or the 

 yielding portion too deep, as mentioned above. 



On ascending an unyielding inclined surface, the two posterior 

 toes never touched the ground ; on descending the same, they 



