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
circumstances, 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 appetite.
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,
potassium, 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, appetite 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 anæmic.
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 appetite, 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 grass for a few days and then
substituted fresh loco plants for grass.
At first the "loco" was refused, but after two or three days the
"loco" was eaten with as much relish as the grass 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 mass 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 appetite, 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 grass. 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 destitute
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 analogous 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 albuminoid 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 mass
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 quantitatively.
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 mass 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 analyzed 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 coarse plants do not act similarly. This fine,
hair-like material was found to constitute 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 portæ and the anæmia 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 hyperæsthesia 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 anæmia 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 anæmia of the brain.
The congestion of the vena portæ commences certainly very early,
but still the first symptoms are the nervous symptoms, first as
excitants, then depressing or sedative, with a marked hyperæsthesia
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 anæmia.[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: