In 1888 Hill reported that a species of Astragalus was acting detrimentally on cattle, goats, and sheep in Cyprus and that these animals fell down as if intoxicated, and also that the natives in time of great drought feed their cattle with this plant mixed with straw, but that they were always made sick until they became used to it.

In 1885 Professor Sayre, of the University of Kansas, undertook the investigation of the loco question. His first report was made in the Transactions of the Kansas Academy of Sciences for 1885, and his reports have been continued at various periods up to 1904. The results of his experiments on various animals--dogs, cats, and frogs[99]--have been entirely negative. He administered alcoholic preparations to himself and took them until they became too nauseous to continue, and found they produced absolutely no symptoms besides the nausea. He suggests, however, that if the plant really is poisonous it is due to its fine hairs, which might mechanically cause death. Sayre has stated that he has sent thousands of pounds of the dried loco plants to various investigators in America and Europe, but all reports were negative as to pharmacological activity. He has, however, done some work on the pure chemistry of the plant and found that the plant contained 10 per cent of moisture and yielded 12.01 per cent of ash. Of this ash, 25 per cent was soluble in water, while 50.6 per cent was soluble in HCl. The insoluble portion consisted largely of silica. He found CaO, K_{2}O, MgO, Al_{2}O_{3}, and Fe_{2}O_{3}, with the acid radicals SO_{3}, Cl, P_{2}O_{5}, CO_{2}, and SiO_{2}.[100] Although Sayre claims that the plant is physiologically inactive, he tried by chemical means to isolate a physiologically active body and, naturally enough under the circ.u.mstances, failed to find one. He claims that while the plant might give alkaloid reactions, he was unable to isolate this body in a pure state, and that alfalfa reacted similarly.

The investigation on animals was continued by Kennedy.[101] He administered an infusion of 1/2 ounce of green _Astragalus mollissimus_ to a fasting dog weighing 23 pounds, but there were no symptoms after 12 hours. A decoction of 1 ounce of the green plant and one of 4 ounces of the dried plant were likewise without action. Extracts with hydrochloric acid were also inactive. When 400 grams of the dried and powdered plant were fed in substance the result was merely to increase the appet.i.te.

The organic acid obtained from 4 ounces of the plant was also found to be inert.

Kennedy did not state in what season the plant was collected and from what locality it was obtained, but says simply that the plant extract was inactive to a dog, a carnivorous animal, and that therefore the plant is nonpoisonous. He adds that death might be due to the tough fibers and indigestible character of the plant. He overlooks, however, the fact that the plant might vary in its toxicity, and he infers from the experiments on carnivorous animals that these results would hold good for herbivora, yet he does not claim that carnivora become locoed in nature.

Kennedy found that the plant lost 80 per cent in weight on drying and that the water extract which represented 30.6 per cent of the powdered and dried plant contained magnesium sulphate and sodium chlorid, tannic acid, gum, coloring matter, an extractive, and a "peculiar organic acid." The ashed plant yielded 20 per cent of ash, consisting of magnesium sulphate, sodium chlorid, alumina, silica, and a trace of iron. "The abundant precipitate produced by the alkaline hydrates, pota.s.sium, sodium, and ammonium was found to consist of magnesium hydrate, an abundance of this base being present in the plant." Kennedy also obtained alkaloidal reactions, but failed to isolate the body giving these reactions.

In 1889 the investigations were greatly stimulated by the report of Doctor Day,[102] then of the University of Michigan. She claimed that she was able to produce marked physiological symptoms, using both _Astragalus mollissimus_ and _Aragallus lamberti_ in her work. She administered daily 60 to 70 c.c. of a decoction[103] of the plants to kittens, together with abundant milk and other food. She states that in two days--

The kittens became less active, the coat grew rough, appet.i.te for ordinary food diminished and fondness for the "loco" increased, diarrhea came on, and retching and vomiting occasionally occurred.

The expression became peculiar and characteristic. Emaciation and the above symptoms progressively increased until the eighteenth day, when periods of convulsive excitement supervened. At times the convulsions were tetanic in character; frothing at the mouth and throwing the head backward as in opisthotonus were marked. At other times the kitten would stand on its hind legs and strike the air with its forepaws, then fall backward and throw itself from side to side. These periods of excitement were followed by perfect quiet, the only apparent sign of life being the respiratory movements.

After a short interval of quiet the convulsive movements would recur. These alternate periods of excitement and quiet lasted thirty-six hours, when the posterior extremities became paralyzed, and the kitten died about two hours afterward. There was no apparent loss of consciousness before death.

The post-mortem examination revealed the presence of ulcers in the stomach and duodenum. Some of the ulcers had nearly perforated the walls of the stomach and duodenum. The heart was in diastole; brain and myel appeared normal. As might be expected from the emaciated condition, the entire body was anaemic.

In a second case 60 to 70 cubic centimeters of a more concentrated decoction were fed daily, with other food as before, to a vigorous adult cat. The symptoms of inactivity, loss of appet.i.te, rough coat, diarrhea, and the peculiar expression of countenance were as in the first case. By the twelfth day the cat was wasted almost to a skeleton, and was correspondingly weak. Paralysis of the hind limbs came on, and the cat died on the thirteenth day. There were no periods of excitement in this case.

These cats developed a craving for the decoction and "would beg for it as an ordinary kitten does for milk, and when supplied would lie down contented."

Doctor Day made controls with healthy animals under the same conditions, with the exception that they received no loco plant. She also fed a young wild jack rabbit on milk and gra.s.s for a few days and then subst.i.tuted fresh loco plants for gra.s.s.

At first the "loco" was refused, but after two or three days the "loco" was eaten with as much relish as the gra.s.s had been. After ten days of the milk and "loco" diet the rabbit was found dead, with the head thrown back and the stomach ruptured.

Subcutaneous injections of the concentrated decoction caused nervous twitchings in frogs and kittens, and if large amounts were used death followed in from one to two hours from paralysis of the heart. The same symptoms were produced in frogs by the injection of an alcoholic extract of the residue left after the evaporation to dryness of the decoction.

In other words, Doctor Day was able to produce a chronic form of loco poisoning with the characteristic symptoms so often described save in the occurrence of diarrhea. Diarrhea is not usually noted on the range.

Sayre had already reported an ulcerated condition of the intestines of a locoed cow similar to that described by Doctor Day as occurring in cats.

Doctor Day urged that the reason previous experimenters failed to produce symptoms was that they had used too small an amount of the plant and that by systematic feeding to healthy cats cases of loco disease may be produced.

Storke states that "Dr. V. C. Vaughan, of the University of Michigan, has since fully corroborated Dr. Day's views."[104]

In her experiments Doctor Day used the leaves, roots, and stems of the plants gathered in September. She believed that the greatest amount of poison is present in autumn and winter. She later undertook the isolation of the active principle, and proceeded as follows:[105]

The roots, stems, and leaves were boiled ten hours, strained, and the decoction concentrated to a sirup, poured, while hot, into a hot flask, corked and set away. At the end of ten days the sirup had separated into two layers--the upper a blackish liquid, the lower a brownish sediment. The liquid was poured into a flask and covered with six times its volume of very dilute alcohol, 30 per cent (the sediment also was washed with dilute alcohol, to insure a complete removal of the liquid), corked, and let stand three days; agitated occasionally, then filtered, and the filtrate slowly evaporated in the air, when crystals were formed. It was found important not to hurry the evaporation, for when this took place too rapidly the crystals did not form.

These crystals are microscopic in size, blue-white in color, and of a variety of forms. The most characteristic are slender and pointed, arranged in rosettes or grouped in various ways. They are soluble in distilled water and very dilute alcohol, very sparingly soluble in strong alcohol, not soluble in chloroform or ether.

The evaporated ma.s.s containing the crystals, when dissolved in distilled water, is slightly acid in reaction. A small amount of this fed to a kitten produced the train of characteristic toxic symptoms--sleepiness, loss of appet.i.te, retching, and diarrhea--that is produced by quite large amounts of the decoction.

The crystals Sayre[106] claims to have already seen. He says that they gave no precipitate with Mayer's reagent, platinum chlorid, or with ammonia, but that barium chlorid and ammonium oxalate gave a precipitate, and he believes that they were in reality an inorganic combination of calcium, so that while Doctor Day may have obtained an extract which produced characteristic symptoms she certainly has not isolated any pure active principle. Later she admitted that it was not possible "to make positive statements as to the chemical character of the active principle."[107]

In 1884 there was a fatal outbreak of a disorder in horses in portions of the Missouri Valley in Iowa, Nebraska, and Dakota. This was almost uniformly fatal in a few weeks or months. The animals lost strength and became emaciated, although they were kept in pasture where there was abundant gra.s.s. There was marked stupor, the animals falling asleep while eating, and they "would remain standing for a whole week, sleeping much of the time, with the head resting upon some object." The post-mortem examination showed that "in every instance there was marked hemorrhagic effusion into the fourth ventricle, the liver and spleen were abnormally dense, the walls of the intestines were almost dest.i.tute of blood, and the stomach enormously distended with undigested food."

The post-mortem find and clinical symptoms suggested to Stalker[108]

that this disorder was due to some plant a.n.a.logous to _Astragalus mollissimus_. He found abundant in these regions _Crotalaria sagittalis_, or rattle-box, one of the so-called loco weeds, and by the administration per os to a young horse of an infusion of 15 pounds of the plant, given in two days, produced the clinical symptoms and the post-mortem condition of the brain which he previously observed on the range.

Power and Cambier[109] undertook the chemical study and the isolation of the active principle of this plant, together with that of _Astragalus mollissimus_. They found that the _Astragalus mollissimus_ if distilled with water yielded a distillate which possessed a peculiar odor, which they thought due to a trace of volatile oil. On distilling with alkali they obtained ammonia and a trace of trimethylamine. In the case of Crotalaria only ammonia was found.[110] They argued that because trimethylamine was not obtained in this case choline was not present. On distilling the _Astragalus mollissimus_ with acidulated water (H_{2}SO_{4}) the distillate was found to contain acetic acid--settling the nature of the "peculiar organic acid" described by Kennedy. From this plant they obtained a resin or mixture of resinous bodies by extracting the plant with alcohol, and after concentration precipitating with acid water. These resins in doses of from 2 to 5 grains failed to produce any symptoms in kittens.

An alb.u.minoid which was obtained by precipitating a concentrated aqueous extract of _Astragalus mollissimus_ by means of alcohol likewise was found to be inactive to a kitten in doses corresponding to 50 grams of the crude plant. A globulin which was isolated by precipitation from a 10 per cent sodium chlorid solution proved also to be inactive in doses of 0.2 gram. They then extracted 3 kilograms of these plants with 1/2 per cent sulphuric acid, and after evaporation to a thick gum the ma.s.s was extracted with strong alcohol, the alcoholic solution was evaporated, and the alcoholic residue taken up in water and precipitated by neutral and basic lead acetates, and after removing the lead with sulphureted hydrogen the filtrate gave precipitates with various alkaloidal reagents. The sirupy residue which they obtained from _Astragalus mollissimus_ by decomposing the precipitate with Mayer's solution administered to kittens in doses of 0.1 gram produced merely frothing at the mouth with profuse flow of saliva, but the animals soon recovered. The presence of a large amount of calcium was shown but not estimated quant.i.tatively.

Power and Cambier summed up their conclusions by stating that both the Astragalus and the Crotalaria contain very small amounts of toxic alkaloids, to which they believe the symptoms of poisoning produced were due. Their work from a chemical standpoint is excellent, but from a pharmacological point of view seems to be deficient; in fact, Power does not claim to be a pharmacologist. What would seem to be the proper course would have been to test for themselves the action of the plant on various animals and, after deciding which reacted most characteristically, test, after various precipitations, both the precipitates and filtrates on various animals to see whether the original symptoms and pathological lesions could be produced. They failed, however, to test their mother substance. It is well recognized that plants grown under varying conditions and on different soils vary in the amount of the physiologically active principle they contain.

In the case of Crotalaria, Power and Cambier had before them the experiment of Stalker, in which he reproduced the disorder by feeding the plant extract to horses, yet they claimed that the body which they administered was the active principle, merely because it produced some frothing at the mouth and salivation in a kitten. The percentage of active principle they found would be too small to account for the symptoms, except in the case of a very active compound.

Certain of these precipitates were also later examined physiologically by O'Brine.[111] He also found the resin precipitated from an alcoholic extract of the plant and also the alcoholic extract from 2.2 pounds of the dried _Astragalus mollissimus_ to be physiologically inactive.

Oatman,[112] using Power and Cambier's method with alfalfa (_Medicago sativa_), obtained a noncrystalline ma.s.s which when given in 0.1 gram dose caused frothing at the mouth in a kitten, but no serious symptoms.

This 0.1 gram represented about 5 pounds of powdered leaves and tops of the plants.

Since the appearance of Power and Cambier's work Sayre has published various papers on the loco weeds in the Transactions of the Kansas Academy of Sciences for 1903-4, vol. 19, p. 194, 1905; 1901-2, vol. 18, p. 141; Seventh Biennial Report of the State Board of Agriculture of Kansas, vol. 12, p. 97, 1891; Journal of the Kansas Medical Society, vol. 4, pp. 222 and 241, 1904, etc. He has contributed nothing especially new, but says that "the old theory that an alkaloidal poison is secreted in the plant causing the loco trouble has not been found tenable," but wishes to be understood that he does not discredit the ground for the opinion that in some mysterious way certain disorders occur in cattle in connection with what is commonly called loco-weed. He suggests that this connection might be somewhat similar to the relationship between the disorder caused by over-feeding half-starved animals on clover or alfalfa[113] and has had the plant a.n.a.lyzed as to its nutritive value, giving the table in the Transactions of the Kansas Academy of Sciences, vol. 19, p. 194. He makes the suggestion that any injurious action the plants may have might be due to the fine, hair-like projections on the plant which mechanically set up irritation. This supposition can be thrown out at once by the experiment of Day and others, who induced symptoms in animals by extracts of the plant, and by the fact that other coa.r.s.e plants do not act similarly. This fine, hair-like material was found to const.i.tute about 33 per cent of the plant on grinding. But Sayre himself does not seem to be positive as to any conclusion. He, like O'Brine and others, has obtained alkaloidal reactions from the plant, but states he has obtained similar ones from alfalfa.[114] At one time he said:

I do not consider loco directly or indirectly the cause of the condition, but am of the opinion that what is called "locoed" is, first, congestion of the brain and spinal marrow (causing blindness and first symptoms), and, second, softening to a greater or less extent.[115] These terms describing the alleged symptoms of "locoism" might occur in well recognized diseases resulting from brain lesions, which latter occur in so-called forage poisoning and poisoning from foul drinking water, etc.

We are not prepared to affirm or deny that the loco-weed produces a train of symptoms characteristic of the plant.[116]

Again Sayre states:

It seems not unreasonable to suppose that the peculiar condition of the animals of the plains, when they gorge themselves with this highly nitrogenous weed, has something to do with the disease. A condition of malnutrition may set in and give rise to the rapid growth of a toxic-producing micro-organism or an irritating principle. This principle may be capable of cultivation and of producing disease artificially. Be this as it may, we feel warranted in saying that the so-called poison is a development within the animal, not a product preexisting in the weed itself.

Sayre also suggests the possibility of the plants producing hydro-cyanic acid, which, it is well known, occurs in sorghum.[117] In the Journal of the Kansas Medical Society (vol. 4, p. 243), he claims to have isolated a crystalline body, but this he has not tested physiologically. Sayre especially deserves credit for keeping the loco investigation alive, and no doubt his change in position is due to his lack of facilities for pharmacological testing.

Carl Ruedi[11] fed rabbits daily by a stomach tube with 10 c.c. of an extract (unstated strength) of _Astragalus mollissimus_ and recorded the following results:

After only five injections one of the rabbits died, and the post-mortem showed to a nicety the congestion of the whole tract of the vena portae and the anaemia of the brain. I put six rabbits under the influence of loco, and the effect was marked, but not rapid, if not given in very concentrated solutions. The solutions were prepared differently, and each of the rabbits had its own preparation, but the effect was nearly the same. In the beginning loco acts as a stimulant; the animals get lively, hilarious, running about; cleaning themselves, etc. This lasts about eight hours, then they become very quiet, sit in a corner of a box, and one can do with them pretty nearly what one likes; they do not move from the place, or just run into another corner, to fall back into the same complacent reverie. One can leave the door open and hammer away at the box, but they do not show any inclination to run away.

During the excitement, however, they become fierce, and I had once the opportunity to watch one of the drollest things possible: One of the rabbits, two hours after dosing it, got loose and ran under a porch. A heavy tomcat came near this hole, and commenced sniffing about; this offended the rabbit highly, and it jumped on the neck of the cat, bit it through the skin, and the cat ran screaming away. When the animals are first under the influence of moderate doses of loco, they suffer greatly from hyperaesthesia of the cutaneous nerves; when one touches them with a stick while lying in a corner, without hurting them, one sees the platysma working away very forcibly, and sometimes they utter sounds of pain. According to my experiments the loco-weed works slowly but surely; as soon as the anaemia of the brain sets in, the animals act in every respect mad like; one hour they are excitable, and then again dull and languid as can be. The rabbits eat, when well, very quickly, and whenever they have opportunity; not so the locoed rabbit; he eats slowly for a minute or two, then he goes into a corner and meditates, comes forward to nibble at a carrot or a piece of cabbage, but he never eats greedily, and does not steal it from the mouth of his neighbor, or only very exceptionally. I observed these rabbits for ten days; they did not die, because I gave them weaker solutions; but they all became very ill, and as I had to leave the park I killed them with the needle inserted into the medulla oblongata, and made the post-mortem. In all of these cases I found great congestion in the abdomen, and marked anaemia of the brain.

The congestion of the vena portae commences certainly very early, but still the first symptoms are the nervous symptoms, first as excitants, then depressing or sedative, with a marked hyperaesthesia of the cutaneous nerves.

Ruedi made an attempt to isolate the active principle and separated a base, which he calls "locoin," from an ether shaking. This base, however, he found to be physiologically inactive, but believes the activity to be due to a body which he calls "loco-acid," which is present in the mother liquid after the shaking with ether. He, however, has not obtained this in any degree of purity and gives no chemical data to substantiate this statement save that the fluid was acid.

Experiments made at the University of Pennsylvania with certain loco plants on cats, dogs, and rabbits proved negative.[119]

Other experiments on rabbits have been made by Doctor Lewis. These rabbits were fed on the leaves, stem, and whole plant, and also extracts of one of the loco plants (presumably _Astragalus mollissimus_) for one or two months, without producing any noticeable effect.[120]

This uncertainty in the results of the investigation as to the cause of the loco disease turned the attention of observers into other lines.

President Ingersoll,[121] of the State Agricultural College of Colorado, in his autopsies on sheep was struck by the presence of tapeworms (_Taenia expansa_) in the gall duct and small intestines. He apparently tried to prove a relationship between the tapeworms and the locoed condition by feeding the extract of a loco plant to sheep, and thus showing its harmlessness. He prepared a decoction from 20 pounds of loco plant (the species was not stated) and boiled this down from 12 gallons to 1 quart. This concentrated extract was fed in three days to a bottle-fed lamb; this lamb showed no symptoms, although kept under observation for two weeks. This theory of the causation of loco by worms was also considered by Curtice,[122] and later brought forward by Steele[123] and Marshall.[124] This idea is very suggestive when considered in relation to the etiology of bothriocephalous anaemia.[125]

Others, again, have claimed that the disease is due to a parasite found upon the loco plants, but all specimens examined by entomologists proved to be harmless.[126]

Lloyd, from his study of the subject, says:

From first to last I have failed in obtaining a characteristic proximate principle, either from the fresh or dried plant. The disease called loco was as murky as the milk sickness so prevalent in the new settlements of Indiana and Kentucky in early days, and, like the numberless herbs that have been presumed to produce that obscure peculiar disease, milk sickness, loco was unresponsive to my chemistry.[127]

It may be safely said that if a specimen of the plant were to be examined in the ordinary manner by a chemist who had no idea of its importance he would report that it did not contain a characteristic proximate const.i.tuent.[128]

Can it be that an admixture of loco and some undetermined plant or earth infected with bacteria taken with the roots, each innocuous under other conditions, can by digestion together in the stomach and intestines result in the production of a poison?[129]

To sum up, it seems to the writer that the poison of loco is a product, and not an educt.[130]