THE MIRACLE OF SMELL.

Otago Witness, Issue 2667, 26 April 1905, Page 28

THE MIRACLE OF SMELL.

Watering some sportsmen partridge-shoot-ing in low ground in the sca-on, one is struck with the marvellous powers of the pointers and retrieveis, in securing a successful bag. In fact, without their extraordinary ability to scent the "living and the shot bird there would be little real sport, i.o far as results are concerned.

With what painstaking assiduity the pointers range among- the green ci - ops until come upon a hidden covey ! At once, as with soldier drill, they make a halt, a foreleg bent in ecstasy and tremor at the finding of the birds. The sportsman knows where to look for hi& next shot : a movement on and in the covey rises, to receive two barels from the lucky man, leaving perhaps a brace or two of their number behind if his .eye is true. The keepers (■ben ■come on with the retrievers to find these birds. Without scent these dogs would be next to useless, yet with marvellous accuracy they track down the wounded.

No doubt there is much in "their instinct,"' so far as sc p nt is concerned : but training does a good deal, and heredity does more. And about this sense of smell little is as yet known. How can the various scents be discriminated? By training druggists can detect them very acutely. Oil of cloves can be detected with one part in 88,000 of water by trained men, whereas the average of females can only detect smell in the solution with one part in 50,000 of water. Men have been able to detect the fusty smell of pruss-ic acid in a solution with one part in two million parts of water. No chemical test could detect this.

The faculty of scent is ver*- acute in certain insects. If a. virgin female of the moth, known as Saturnia Ca.vpini, is shut up in a box, males of the same species will trace her out for a mile through the multi-odoured air of the wood. But the hoemt of dogs seems to eclipse all in its marvellous results. The late Dr Gr. .T. Romanes gave to the scientific world the results of some intei'ssting experiments which hp made to •a.'Jcertam the character of the intensely-developed sense of smell in some dogs. Ho had a remarkable terrier which showed the almost supernatural capabilities of this sens©. Even when the London paiks were swarming with pedestrians, and the terrier was having its own conversation with some other dog, and he would zigzag about and hide, the animal would Efo to the place wh&re it had last seen its master, and there, picking 1 up the scent, would track his footsteps over all the meanderings he had made until it reached his retreat with joy.

Now comes the interesting question, "What is the source of the scent?" Is the doe guided by some distinctive smell attaching to its master's shoes, by any distinctive smell of its master's feet, or by both of thes9 differences combined? By careful ■experiments it has been shown that a sensitive dog" will follow the track of a man who is wearing' its master's boots, and will reject the tmok of its master who has on strange boots. If a layer of stiff brown paper is glued to the soles and sides of the usual shooting boots the dog will not follow its master's track ; but when the paper get& worn through at the heel and the boot touches he ground the scent is caught at once and speedily followed up.

On one' occasion Dr Romanes put a most intelligent bitch to a crucial test. He walked for 50 yards in his ordinary shooting boots ; Mien he walked a hundred yards in his stockings, and completed another hundred yards on his bare feet. The bitoh followed the first part of tlie trail at full speed.

Changing the experiments, he soaked his ordinary shoofcina 1 boots wiMi ' the oil of anifieed and walked with these over the park. Strange to say this strong odour did not interfere with the bitch's s<?enfc, for it ran him down as quickly as before. Accordingly this keen observer came to the oonolusion that his setter distinguished his trail from that of all others by the peculiar* smell of his boots, and not by the particular scent of his feet or body. The exudations from his feet required to be combined with shoe leather ; and brown paper can stop the transmission of thai scent. The sceniu.

moreover, ia not destroyed by the strong smell of aniseed or by that of many other footprints. There is> an odour conveyed through the air to dogs from tiie person which can be detected even up to distances of 200 yards ; but experiments in that line arc very difficult of verification. All know the wonderful power a. pugi hab in detecting by scant where a bit of bUcuit has been hidden in the drawing 1 room — for that animal's whole life sooiiic concentrated upon the gratification ot iis stomach — and the all-absorbing pa&s-ioii of a terrier at" a ditch where rats abound. It looks all excitement, impossible to be restrained. A rabbit may cross a main road, and a sensitive dog', coming a good while afterwards, will bolt off at once to search for its prize.

How infinitely minute must bo the particles that emanate from the object which the dog is~ tracking ! Yet matter is extremely divisible. The tenth part of a grain of musk will continue for years to fill a rcom with its odoriferous particles, and afc the end of that time will not be appreciably diminished in weight by the finest balance. A cubic inch of air rising from the flaaiiio of a Buneon burner has been found to contain no fewer than 489 millions of dust particles. A drop of blood which might be suspended from the point- of a needle contains about a million of red flattened corpuse!<-s. Still, though matter is so marvellously divisible, the olfac-toiy nerves are infinitely more sensitive Much has yet to be investigated with regard to the differentiation of the points in tlwpe nerves so that they may discriminate with such apparently miracukms acouvaev • yet even the reseults in the scent of doe.s show how marvellously fine is their discriminating power. Our sense of smell, unless in the trained* chemist, is not -oven so acute a? that of the semi-savage. The aborigines of Peru can, in the darkest night, and in the thickest woods, distinguish respectively a white man, a negro, and one of their own race by the smell. Much we have gained by civilisation : but not without some less to our bodily energies and senses. Alan's recuperative power after an injury is in the- inverse ratio to his social advancement. Similarly, he seems to become lees acute and delicate in th" eensc of smell as he fares 1-ctter and lives more comfortably. The faithful dog puts him to shame. — Daily Mail.