Part 8

O'Brine, D. Progress Bulletin on the Loco and Larkspur. Colo. State Agric. Coll. Bul. 25, p. 12. 1893.

Faville, in O'Brine, D. Progress Bulletin on the Loco and Larkspur. Colo. State Agric. Coll. Bul. 25, p. 11. 1893.

Sayre, L. E. Loco Weed. Amer. Vet. Rev., vol. 11, p. 559. 1887.

Stalker, M. The "Loco" Plant and Its Effect on Animals. Bur. Animal Industry, 3d Ann. Rept. (1886), p. 274. 1887--Sayre, L. E. Loco-Weed. Amer. Pharm. Assoc. Proc., vol. 38, p. 108. 1890.--O'Brine, D. Progress Bulletin on the Loco and Larkspur. Colo. State Agric. Coll. Bul. 25, pp. 16, 17. 1893.

Mayo, N. S., l. c., p. 118.

Ruedi, C. Loco Weed (Astragalus Mollissimus): A Toxico-Chemical Study. Trans. Colo. State Med. Soc., 1895, p. 418.

Sayre, L. E. Loco Weed. Amer. Vet. Rev., vol. 11, p. 559. 1887.

O'Brine, D. Progress Bulletin on the Loco and Larkspur. Colo. State Agric. Coll. Bul. 25, p. 12. 1893.--Klench, J. P. Rattleweed or Loco Disease. Amer. Vet. Rev., vol 12, p. 399. 1888.

Anderson, F. W. Poisonous Plants and the Symptoms They Produce. Bot. Gaz., vol. 14, p. 180. 1889.

McCullaugh, F. A. Locoed Horses. Journ. Comp. Med. and Vet. Archives, vol. 13, p. 436. 1892.

=HISTORICAL SKETCH OF LOCO INVESTIGATIONS FROM A PHARMACOLOGICAL STANDPOINT.=

During the western immigration of 1849 the Indians along the Missouri River described to the immigrants a plant (Astragalus mollissimus) producing death in horses and cattle, which was preceded by various forms of excitement.

The attention of the United States Department of Agriculture was first called to the toxic action of the loco plants in 1873, when specimens of the plants, which were identified as Astragalus hornii and A. lentiginosus, were sent from California by Mr. O. B. Ormsby, with the statement that they were poisonous to stock, especially to horses. Mrs. J. S. Whipple also corroborated this information. The botanist of the Department, Dr. George Vasey, published a note and requested further information concerning the plants. These notes were enlarged by a similar contribution by Dr. P. Moffat on Aragallus lamberti. The following year Vasey reported with more fullness, and his description of the action of the plants is substantially what we find in most of the books of to-day.

In 1876 Lemmon noted that Astragalus mortoni was "a deadly sheep poison." At the same time Rothrock, botanist of the United States Geographical Survey under Lieutenant Wheeler, described these plants, and Kellogg, a botanist in California, reported that Astragalus menziesii was causing great losses in horses, sheep, and cattle and claimed that the stockmen had been familiar with this disorder for at least ten or fifteen years. This report of Kellogg was followed by that of Rothrock in 1877.

In 1876 a specimen of Aragallus lamberti was sent from Colorado to Professor Prescott, of the University of Michigan, under the name of "crazy weed," with the statement that it was poisonous to horses and cattle and that, while the Mexicans often used it in making beer, it sometimes caused symptoms in men. His pupil, Miss Watson, undertook a study of its chemical properties. She failed to isolate any pure chemical compound, but claimed that in the root there was a body giving alkaloidal reactions and that there was also a resinous body present. Another of his pupils, W. R. Birdsall, took the ground-up root himself in doses of 20 grains at various intervals for several days and later 40-grain doses in one and a half hours, but without experiencing any marked symptoms except colicky pains. A kitten also was given about one and a half ounces of the fluid extract without effect. Prescott sums up by saying that "it would seem that the dried ground root possesses no poisonous properties." The work of Miss Watson was considered of sufficient importance to be abstracted in the Annual Report of the Commissioner of Agriculture for 1878 (1879), page 134.

Gradually the Department of Agriculture became more and more interested in this subject, and Peter Collier, chief chemist, in 1878, examined the roots and leaves of Aragallus lamberti for alkaloids, but found none.

In 1880 Peter Collier published a proximate analysis of Astragalus mollissimus made by Francis A. Wentz, of Kansas. His investigations showed it to have an ash content of 6.76 per cent, while the Aragallus lamberti, analyzed by L. F. Dyrenforth, of Chicago, showed an ash content of 4.32 per cent. Collier sums up by saying:

From the additional work done at this Department it seems probable that the deleterious effects observed from animals eating this plant may be due principally to the fact that the sweet taste causes cattle to reject more nutritious food and strive to subsist upon the Oxytropis only. This plant is mechanically a very unfit substance for food, being of a tough, fibrous, and indigestible character. It is possible that, when the animal becomes somewhat enfeebled by lack of proper nourishment, the small amount of alkaloid may have a direct poisonous action. Again, it seems probable that the plant may contain much larger proportions of alkaloid at certain stages in its development than at others, or the seeds may prove to be the most injurious portion.

The departmental work was continued by further short notices by Vasey in 1884, 1886, and 1887, and by the report of Stalker in 1887. This report by Stalker is still the best description on the clinical side of the question.

Rothrock, meeting the loco plants in his survey work, describes their effects on animals as follows:

Certain it is, however, that, once commenced, they continue it, passing through temporary intoxication to a complete nervous and muscular wreck in the later stages, when it has developed into a fully marked disease which terminates in death from starvation or inability to digest a more nourishing food. The animal toward the last becomes stupid or wild, or even vicious, or, again, acting as though attacked with "blind staggers."

Under the name of Crotalaria, H. Gibbons, in 1879, refers to a plant growing in California which it was claimed was producing characteristic symptoms of poisoning in horses and sheep. This plant Professor Maisch afterwards identified as Aragallus lamberti.

Dr. Isaac Ott undertook the physiological study of the question and used an alcoholic extract of Astragalus mollissimus. He found from its action on frogs, rabbits, and cats that the plant had decided physiological action, as follows:

(1) It decreases the irritability of the motor nerves.

(2) Greatly affects the sensory ganglia of the central nervous system, preventing them from readily receiving impressions.

(3) Has a spinal tetanic action.

(4) Kills mainly by arrest of the heart.

(5) Increases the salivary secretion.