to vary slightly in different parts of the State. In the Judith Basin and in the Sun River country it does not grow plentifully on the level prairie, while in these same regions the foothills are so completely covered with it that they appear as large white tracts when the plant is in full bloom. On the other hand in the range country along the course of the Musselshell River the white loco weed is met with more extensively on the high prairie ranges. Attention has already been called to the fact that as a general rule native ranges are freer from poisonous plants the farther one goes away from the mountains. This statement is also true of the white loco weed, which seldom occurs abundantly on any prairie range in Montana at a distance of 20 miles from the mountains.

HISTORY AS A POISONOUS PLANT.

For many years a disease called loco, affecting cattle, horses, and sheep, has been generally known to the stockmen of the western ranges. This disease has most commonly been attributed to the action of certain plants, more rarely to that of alkali. Several species of plants have been suspected of producing the loco condition in animals and have been called loco plants or loco weeds and also crazy weeds from the nature of the disease. Nearly all of the plants which have been considered loco weeds belong to two genera of the pea family, Astragalus and Aragallus. These genera are represented by numerous species on the western stock ranges. Most of the species are somewhat restricted in their distribution either to the southern or northern portion of the range country, or grow more abundantly in one region than in another. In Colorado the plant which is most commonly known as loco weed is Astragalus mollissimus. In Montana, on the other hand, the plants most generally called loco weeds by the stockmen are species of Aragallus. A number of other plants have occasionally been mistaken for loco weeds, and among these may be mentioned species of Astragalus and lupine. The species which is most concerned in causing the loco disease in Montana is Aragallus spicatus and is closely related to A. lambertii.

It is the belief of a number of stockmen that a condition almost, if not quite, the same as the loco disease may be produced in sheep by eating undue quantities of alkali soil. Reference has already been made to the fact that some stockmen do not salt their animals at all, or only at long intervals. When animals are not salted regularly they soon discover localities where large quantites of alkali are found in the soil and visit such places frequently for the purpose of eating this alkali soil. A few of the more observant sheep raisers have come to believe that sheep are less apt to become locoed when regularly salted than when they eat large quantities of alkali in consequence of not being supplied with salt. For this fact two explanations have been offered.

On the one hand a number of sheep raisers believe that the eating of large quantities of alkali is itself the cause of the loco disease. A few sheep men have maintained that the locoed condition is in every case due to eating alkali or to drinking strongly alkaline water. This assertion is definitely disproved by the fact that sheep and horses are known to have become locoed while feeding on mountain ranges where no alkali soil was to be found and where all of the water was free from alkali. A considerable number of sheep became locoed while feeding on a range of this character on the slopes of the Rockies near Augusta. Mont. No alkali was to be found on this range in either soil or water. These sheep were removed to another range where the loco weed did not grow so abundantly, but where all the water was somewhat alkaline. Their condition improved slightly under the changed conditions. although they were still able to find and eat the loco weed in small quantities.

On the other hand, an equally large number of sheep men believe that there is no connection between the loco disease and alkali. A second explanation for the observed fact that sheep most frequently acquire the loco habit when not salted is that the lack of salt and the physiological action of the alkali may bring about a depraved appetite which manifests itself in the formation of the loco habit. As already stated in a previous part of this report,' the different forms of alkali, such as are found in Montana, can scarcely be considered substitutes for common salt in the animal economy. Disturbances in the normal physiology of animals are likely to result in the majority of cases from total absence of salt. It is well known that a number of diseased conditions in animals are accompanied with manifestations of a depraved appetite. From a general description given of the loco disease it is apparent that this condition might very justly be termed a perverted appetite. It has, to be sure, not been demonstrated by actual observation that the depraved appetite which is shown in the formation of the habit of eating loco weeds is in every instance the result of the first taste of these plants. A number of observations made by the principal sheep raisers and by ourselves indicate, as already stated, that sheep more frequently form the habit of eating the loco plants when not regularly supplied with salt than when abundantly furnished with this substance. All reliable observations point to the conclusion that it is highly desirable to supply sheep with a sufficient quantity of salt, which they can get whenever they wish it.

It has been frequently suggested that the peculiar effects produced by eating loco weeds are due to inadequate nutrition. In such a theory it is of course assumed that the loco weeds do not contain the elements necessary to the diet of a sheep or horse. The proof of this assertion is not forthcoming, and it seems more reasonable to believe that the

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