to powder. If, however, you drop in three or four other small pieces of chalk or dry clay and especially one or two pieces of squarish bits of stone, or any small object with a rather rough surface and some corners on it, you will find that you can grind the clay or chalk into powder nearly twice as rapidly, and that you can even break up grains of corn, thin-shelled hazel-nuts and walnuts in this curious form of mill, and this is precisely the meaning and action of this tremendously thick-walled pouch at the end or "door" of the stomach. The food is here ground into powder, after being softened and soaked in the crop and stomach instead of before, as in animals. Nature can make a grinding-apparatus at any part of the food-tube where it seems most desirable. With this exception and addition of a pouch-like swelling of the gullet, at the lower part of the neck, where food can be stored and soaked before being passed on to the stomach, the bird food-tube is practically the same as the animal's. It matches the character of the food in precisely the same way, for in birds which live upon flesh or fish or soft bodied insects, the walls of the gizzard are extremely thin, because such food after being torn up by the beak needs comparatively little grinding and the length of the food-tube is short in proportion to that of the body. In the grain-eating birds on the other hand, its walls are extremely thick and strong, because their food cannot be properly melted for absorption until it has been ground, and the food-tube is long in proportion to the length of the body, just as in grass- and graineating animals. As an instance of how quickly a food-tube can adjust itself to change in the diet, it has been found that the gulls in the north of Scotland, which during one part of the year live largely upon grain and seeds, and another part of the year chiefly upon fish, grow a much thicker walled gizzard during the time that they are living on grain than they have in the other half of the year when they live upon fish. Curiously enough, in the ant-eaters, some armadilloes and other animals of that class, which have lost their teeth and hence are known as "edentates," the lowest part of the stomach has become greatly thickened and lined with horny plates almost exactly like a bird's gizzard. As we have seen that our own teeth are intermediate between those of the flesh eaters and those of the grain eaters, although much nearer to the former than the latter, so our food canal is also intermediate between the two, although it is so little removed from that of the dog that nearly everything that we have said of the dog's food-tube is true of our own. Our stomach is a little larger, on account of the larger amount of potatoes, vegetables and such like bulky foods that we eat, but its shape is almost exactly the same, and our food-tube, for the same reason, is about six times the length of our bodies instead of about five times as in the dog. But we again come under precisely the same rules as the rest of our animal cousins in this respect, for negroes and other races of men living in warm climates where there is abundance of vegetable food, such as rice, bananas, yams, maize and fresh fruits, to be had the year round, and whose diet is in consequence more largely vegetable than that of our northern races, have added about another body's length to their alimentary canal. The same sort of lengthening has been proved to take place in the food-tubes of poor children in the city slums, who are fed upon coarse, innutricious and indigestible food. In them the canal may actually become ten or twelve times the length of the body. It is said by some observers that the Esquimaux, in the frozen North, who are compelled by their climate to live almost exclusively upon animal food, and that very largely in its most concentrated form of fat or oil, have shortened theirs nearly a body's length. You must not however conclude, from what we have seen of the shape of the dog's canal, that his food is or ought to be entirely meat or flesh. There are very few animals indeed that live absolutely and entirely upon a flesh diet. Those who take their flesh in the form of fish, such as the seals, some fishes, and the flesheating birds, are almost the only ones. Even when wild, although two-thirds or three-fourths of his diet consists of the flesh of animals and birds that he can capture, the dog also eats a certain amount of fruit during the season. Indeed the best place to find tracks of wolves, foxes and bears in the height of summer is in the patches of wild raspberries, wild cherries, salmon-berries and so forth, and later in the groves of wild plum trees. Some dogs will even go so far as to crack and eat nuts when they can find them, and nearly all these wild animals when captured, if given bread or sweet-stuff or even potatoes and carrots will eat them in fair quantities. I dare say most of you have seen dogs biting off blades of grass and swallowing them, but this is not for food, merely their way of taking medicine for certain digestive disturbances. Since the dog has become domesticated, sleeps for the most part under cover, spends a good deal of his time in-doors and has only about half the need of exercise or the opportunity for it, that he had in the days when he would find his breakfast on foot, on waking in i the morning, he no longer needs such a concentrated, highly nourishing and stimulating diet as one of pure meat. Indeed, too much meat will seriously upset his digestion, and, fanciers assure us, give him that unpleasant "doggy" smell, which is the principal objection to his being received in the parlor, as a member of the family. A diet consisting of a mixture of animal and vegetable foods, meat and bones with potatoes, rice, oatmeal, breads and biscuits of various descriptions will be found to be the best for his health under domestication, and though sugar forms but a very small part of his diet, when in a state of nature, only during the short fruitseason in fact, yet a small amount of it in his food is of great importance and one of our best known brands of dog biscuit owes part of its value to the fact that it contains sugar in the form of dates. In fact, so closely does the dog's alimentary canal correspond to our own that when he is brought under domestication and housed and "cityfied" as we are, he thrives best on almost precisely the same diet that we ourselves use. There is no better food for any dog than an abundance of household scraps, and dogs in kennels who are fed in large numbers, upon specially prepared and purchased foods, seldom thrive as well as those who get the "littleof-all-sorts" diet which any household scraps can give in perfection. As for the dogs and their cousins the bears, in captivity, a well-mixed diet, like our own, is found to agree with them far better than a purely animal one. Of course here as everywhere else, the food fuel must be regulated according to the kind and amount of work required of it, and for hounds and other hunting dogs, setters, collies, and dogs that are used to draw carts and wagons, larger quantities, in proportion, of meat and larger total amounts of food are required, than in the case of pet and lap dogs of all sorts, or the ordinary city dog, who is confined for the most part to a small yard and has only an occasional formal run of an hour or so as an apology for exercise. The more nearly vegetative a dog's existence becomes, the lighter and more vegetable should his diet be. In fact, some unfortunate little wretches of lap dogs, toy spaniels and pugs, can only be kept alive at all and in any temper short of fiendish, by cutting down the meat in their diet almost to the vanishing point. Some of them are kept by fanciers, when training for a particular beautiful coat of hair, for show purposes, upon a diet of toast, dipped in tea, or milk-and-water; shavings, instead of sea coal, under their boilers. PROFESSOR HAECKEL AS AN ARTIST. S BY THE EDITOR. OME time ago we called attention to Professor Haeckel's work on Art Forms in Nature which was appearing in installments, and now we make the announcement that the work has been completed and lies before us in a stately folio volume, containing 100 VIEW FROM THE RAMBODDE PASS. After a photograph from Haeckel's Wanderbilder. 4535 plates, many of them colored, and accompanied by descriptive text.* The elegant beauty of some of the lower forms of life is sur* Kunstformen der Natur. Leipsic, 1906. 1 |