152 DIVEK their resins and volatile oil. Their therapeu- tic effect is due rather to the alterative action of the urine bearing these constituents on the mucous membranes by which it is excreted and over which it passes, than to any increase in its amount. Benzoic acid passes into the urine in the form of hippuric acid, and may be used when it is desirable to increase the acidity of that fluid. Digitalis, although frequently used as a diuretic, is probably only secondarily so. It increases the flow of urine by virtue of its action upon the arterial tension of the kidneys, promoting thereby a more rapid flow and even distribution of the blood through them. Digi- talis is frequently combined with squill. Diu- retics are used in various stages of kidney dis- eases (where they should be very cautiously managed), in gout, rheumatism, dropsy, and affections of the urinary passages. Although very useful and efficient in many cases, they cannot always be relied upon, and consequently are not regarded as among the most certain of medicines. It is well known that many wines, especially hocks and acid wines, are apt to run off by the kidneys. Ardent spirits, especially gin and whiskey, will also increase the urine, but neither wines nor ardent spirits are often prescribed as diuretics. DIVER (colymbus, Linn.), a bird of the order natatores and family colymbida, the latter con- taining the divers and the grebes. The bill in this genus is long, strong, straight, curved slightly at the tip, which is sharp, with com- pressed sides ; the nostrils are in a membra- nous groove; the wings are moderate and pointed, the first and second quills the longest ; the tail is very short and rounded ; the tarsi rather short, compressed, and covered with reticulated scales ; the toes long, the three ante- rior united by an entire web, and the inner side of the internal toe margined with membrane ; the hind toe short, with a small membranous margin; the claws moderate, depressed, and broad. Only three species are well ascertained, the C. glacialis, C. arcticus, and C. septentri- onalis (Linn.), which belong to the arctic circle, migrating to the northern temperate regions of America and Europe. The great northern diver, generally called loon in the United States (C. glacialis), is a large, pow- erful, and handsome bird; the largest males measure about 3 ft. to the end of the tail, with an extent of wings of nearly 5 ft., and a viirht of from 8 to 10 Ibs. The head is mod- erate, narrowed in front ; the neck thick and long ; the body elongated and depressed ; the t'.-i-t very far back; the plumage short and dense. The bill is black, iris deep bright red, t'rrt grayish blue, with the webs brownish Mark ; tin- ht-ad and neck are dark greenish Mm-, with purple reflections; on the throat then- is a transverse white patch, with longi- tudinal dusky streaks; in the middle of the ncrk an- t vo white patches, continuous behind, but separated an inch in front ; the sides of the neck at the lower part are streaked longi- tudinally black and white, there being on each feather two oblong spots of the latter hue ; the upper parts are glossy black, with spots of white in regular transverse curved lines with 1. The Great Northern Diver (Colymbus placialis). 2. The Red-throated Diver (C. septentrionalis). the convexity backward, the spots being round- ed and small toward the neck, sides, and tail coverts, larger and quadrangular on the middle of the back, largest on the scapulars; the lower parts are white, except on the sides under the wings, which are black with ellipti- cal white spots, a faint dusky band across the vent, and the lower tail coverts, which are blackish, tipped with white ; the tail is brown- ish black, with a paler tip. The female re- sembles the male in colors, but is smaller. The young in winter are dark grayish brown above, white underneath, with the sides dusky ; toward spring the white spots begin to appear, and the plumage is that of the adult at the end of summer ; the go further south than the adults. The flight is rapid, long sus- tained, and at a considerable elevation. The gait of the bird on land is generally slow and awkward ; on the water, when at ease, it swims lightly, but when alarmed it sinks the body so deeply that not more than inch of its back can be seen. As a diver it is unsurpass- ed except by the darter and the auk, disappear- ing quickly, flying rapidly beneath the surface, remaining under water a long time, and coming up again at a great distance from the spot of its disappearance. Loons are occasionally found drowned in fishermen's nets, and are sometimes caught on hooks. The curiosity of the loon is often taken advantage of to draw them within shot, as the bird will almost always approach any bright-colored object waved by a con- cealed gunner; hence the phrase "stupid as a loon." Its notes are so loud and plaintive that to be " as noisy as a loon " has become a prov- erb. Its food consists of fish, lizards, frogs, aquatic insects, and the roots of fresh-water plants ; it fishes in both salt and fresh water, and usually swallows its food beneath the surface. The flesh is tough and rank. The loon breeds
