3 62 THE POPULAR SCIENCE MONTHLY. 



dors, by what we might call locomotive memory i. e., the faculty to 

 remember a long series of turns in their due sequence and with the 

 correct intervals of time or space. The sense of touch becomes here 

 vicarious to eyesight. In the same way a wide-awake animal might 

 take cognizance of certain locomotive data without the assistance of 

 its eyes. It might feel the turnings of its rolling cage, and remember 

 enough to imply the general direction. A stupefied animal could not 

 do it. The olfactory power of a dog exceeds ours about as much as 

 human eyesight exceeds that of a shrew-mouse. A dog will " set " a 

 covey of partridges across a broad field, and can scent a tramp from a 

 distance of half a mile. A nose that can track the faint scent of a 

 rabbit through thickets of aromatic herbage might easily distinguish 

 the atmosphere of a reeking manufacturing town at a distance of ten 

 miles. At fifty miles it might be barely possible under the most favor- 

 able conditions of wind and weather ; at one hundred and fifty miles 

 it seems impossible under all circumstances. Besides, a dog would 

 find his way to a backwoods cabin as readily as to a smoky metropolis. 

 The question still recurs : How does he manage it ? Should dogs be 

 gifted with the faculty of determining geographical latitude and longi- 

 tude by means of their noses ? 



The memory-hypothesis being disposed of, the scent-theory might 

 be definitely settled by a simple operation, viz., destruction of the 

 olfactory nerve. Any anatomist could do it. Helmholtz and Von 

 Graefe made similar experiments with the optic nerve, even without 

 inflicting permanent damage. A dog might be rendered scentless for 

 a day or two, and a trip to the next county under the above-described 

 collateral precautions would decide the point. Deerhounds, pointers, 

 and terriers would be the best subjects. for the experiment; grey- 

 hounds are not only inferior in acuteness of scent but in sagacity in 

 general ; and collies and poodles, though marvelously clever in their 

 peculiar spheres, seem to be almost destitute of what the French call 

 the sens tf orientation (the sense of orientation the process of deter- 

 mining the points of the compass). 



Leaving the exegetical question out of view, I will here venture a 

 conjecture in regard to the origin, or rather the original purpose, of 

 the strange faculty. The common ancestor of all domestic dogs was 

 probably some near relative of the Canis lupus, either the dog-wolf 

 of the Hindoo-Koosh, or the Canis aureus, the Indian or African 

 jackal. The puppies of all these canines are born in litters from six 

 to ten at a time, are helpless for the first ten weeks, and entail a great 

 amount of trouble on their food-purveyors. The mother, perhaps 

 straitened in her own means of support, has now to meet the demands 

 of a greatly enlarged household, and in all probability the available 

 supplies of animal food in her next neighborhood will soon be ex- 

 hausted. Her forage excursions must be extended to greater and 

 greater distances, in a barren country like northern Africa or Turkis- 



