THE RELATION OF DIET TO DISEASE
BY
DR. E. P. CORSON-WHITE
Food in the widest acceptation of the term, means every thing ingested
that goes, directly or indirectly, to growth, repair of the body, or
production of energy, all of which phenomena must continue when food is
withheld or supplied in insufficient quantities. Under the latter
condition the processes go on at the expense of the body tissues as
these are protected only when the diet is adequate in every way. A
proper diet, therefore, must be one on which an animal will attain
maximum development, maintain a normal weight curve, show a minimum
susceptibility to disease, live out a full term of life, breed normally,
and rear healthy offspring, capable of normal independent life after
they are weaned. It must fulfill the caloric needs of the body, and in
young animals it must also supply the growth impulse. In its physical
properties it must fit the morphological demands of each type of
gastrointestinal tract. In its chemical content it must supply all the
elements found in the body in usable form, and in amounts sufficient to
cover the needs of the body for growth, repair and waste. To evaluate
fully the influence of food on the individual animal it is necessary to
study its relation: (1) to the type of alimentary tract, (2) to the type
of bacterial flora and their metabolic processes, (3) to the chemical
needs of the body, (4) to the changes arising in the catabolism and
anabolism of all types of food, (5) to exercise or its lack, keeping in
mind always the constant interdependence of all factors. Our knowledge
of nutrition has to a very large extent paralleled the advances in
chemistry, especially the researches into the structural makeup of
living cells, the intermediate stages in their upbuilding and
degradation and the products resulting from their physiological
activities.
Incorrect feeding both qualitative and quantitative undoubtedly plays an
important rôle in producing disease. In the early works on nutrition,
the proportion of fats, carbohydrates and proteins was regarded as the
essential point of a normal diet. The researches on the composition of
foods marked the first real epoch in this history and Fischer’s[57]
studies on the variation in the composition of proteins from different
sources first introduced the idea of quality. Later Mendel and Osborne
investigated the biological values of purified proteins, while at the
same time McCollum and others were studying the value of the groups of
proteins occurring in a single natural food stuff, were calling
attention to the so-called vitamines, and were emphasizing the need of
balanced inorganic materials. These studies have practically
revolutionized our knowledge, particularly of the effects of badly
balanced foods. They have clearly demonstrated that dietary values can,
in all probability, be discovered only by careful biological study of
feeding experiments together with the finer analysis of the components
of the diet, especially of the protein and fat radicles. At the same
time a definite appreciation of the rôle of each element in metabolism
must be kept in mind.
These varied studies on nutrition have shown that the chemical
requirements of a diet are in their ultimate analysis essentially the
same for all species of the higher animals—that is all require
approximately the same amount of protein, fat, carbohydrate, etc., per
kilo of body weight, while the morphology of the tract decides the
physical properties of the diet.
RELATION OF FOOD TO ALIMENTARY TRACT.
Food derived from animal sources is high in protein, readily digested,
and highly putrefactive. This type of diet is suited to an alimentary
tract which permits rapid passage through its length, and is fitted with
sturdy walls. The gastric section is simple, the intestine short and
narrow with ill-defined separation of its parts into small gut, cecum
and colon. This type is found in all land Carnivora. The fish-eating
carnivores have a strong tubular stomach and an enormous length of
intestine, but no cecum. The omnivores occupy a middle place. In them
the alimentary tract consists of a simple stomach, a short wide
intestinal tube, and a more complex, although still comparatively
simple, cecum which is generally longer than that found in the
carnivores. This tract is too small to manipulate the bulky vegetable
masses necessary to provide their minimum protein requirement, and too
long and complicated to dispose quickly of the putrefactive animal
tissue. Among these animals colitis is common, due to the fact that the
shape and position of this part of the tract favors stasis, or at least
a sluggish movement of its contents at a point in the digestive scheme
where the food residue is rich in protein by-products, ready for
bacterial growth.
The herbivores with food derived from plants which requires a long
period of time for its digestion, have, on the other hand, voluminous
stomachs, or large ceca or both; and very long small intestine. In this
tract the concentrated food of the carnivores would provide an
enormously excessive protein intake or if only the protein requirement
is supplied would leave the tract so empty that it would be unable to
functionate.
All studies in comparative anatomy demonstrate the fact that while
neither a complex stomach nor a large cecum is essential to the
digestion of vegetable food, a capacious and complex alimentary canal,
as a whole, bears a relation to vegetable diet, particularly in the
mammals. Either a highly developed concentrated glandular apparatus is
added to the stomach, as in the wombats, beavers and dormice, or the
stomach is subdivided, sacculated, or otherwise amplified as in the
ruminants and herbivorous marsupials. Sometimes both complexities are
combined as in the case of the sloths. If the simple stomach is
retained, it is supplemented by a large sacculated colon or cecum, as in
the horse. In birds, the proventricle is larger in meat- and fish-
eaters, while the gizzard is more muscular in grain- and insect-feeders,
and the intestines are longer in those devouring coarse green grass and
leaves. The length of the ceca is related entirely to the diet, the long
ones corresponding to the diet which needs protracted periods of time to
exhaust its nutriment.
THE BACTERIAL FLORA.
The bacterial flora harbored in the intestinal tract is closely related
to the type of food and to the character of the alimentary tract.
Levin[58] found sterile intestinal tracts in white bears, seals,
reindeer, eider ducks and penguins when in the Arctic regions; but these
same animals when they are brought to a temperate climate rapidly
acquire intestinal bacteria. The function of the normal inhabitants of
the tract is, probably, to protect the body against invasions of
obnoxious species. Herter found in man that a few species adapt
themselves to the digestive tract and control the growth of newcomers
capable of doing injury. These common varieties become a source of
danger only when present in large numbers.
Bacteria which produce decomposition of food in the digestive tract are
of three types: (1) Pure putrefactive anaerobes, (2) organisms both
fermentative and putrefactive, but tending generally to antagonize the
putrefactive anaerobes, and (3) fermentative organisms. In the stomach,
fermentation of carbohydrates with the production of organic acids is a
frequent occurrence. Putrefactive types are very rare except with
pyloric stenosis, a condition which favors excessive fermentation by
diminishing the tone and motility of the stomach and the amount of
hydrochloric acid. This condition is further increased by excessive
carbohydrate food. In general the products of fermentation tend to
restrict putrefaction, yet both may be operative. In the small
intestines, bacteria are always present because of the protein richness
of secretions, the rapid digestion of food and the slight or ineffectual
antiseptic properties of intestinal juice, bile and pancreatic
secretions. The putrefactive bacteria rapidly increase and decompose any
protein that is unabsorbed—a process most marked in the colon because
its shape and position favor stasis or slow movement of its contents. In
general the greater the amount of unabsorbed and digestible protein and
the longer the material stays in the intestinal tract, the greater the
putrefaction. The meat-eating animals develop Gram-negative bacilli,
while the carbohydrate-eaters show a predominance of Gram-positive
types.
Ingested food never contains the enormous amount of bacteria found in
the feces. The alimentary tract with its contents forms a most
efficiently combined incubator and culture medium, in which bacterial
growth exceeds that of any known location both in intensity and
complexity. The range of reaction and composition of nutritive
substances at different levels of the intestinal tract is such that a
great variety of bacteria capable of growth at body temperature develop.
The prominent types that appear in the flora of each order of mammals
are fairly constant in their occurrence. They depend primarily on food
ingested, and show well marked seasonal variations, dependent again on
changes in food. Faulty feeding may itself give rise to a toxic
condition of the gastrointestinal tube, and thus often prepares this
soil for the development of organisms.
The intestinal flora also changes along rather definite lines as the
diet of the host changes from the monotony of the infant to the variety
of the adult. At birth the tract is sterile, but bacteria soon make
their entry through the mouth in food and water. The majority of these
organisms pass to the stomach where many are destroyed, but a number
travel to the intestines where they may gain a foothold. There is always
a mechanical transportation of intestinal bacteria from higher to lower
levels. A continued preponderance of protein in the diet of all animals
leads to a partial or complete suppression of the Gram-positive acid-
forming groups and an increase of the proteolytic Gram-negative types;
while on the other hand an excess of carbohydrate leads to diminution or
suppression of proteolytic activity and an increase in the fermentative
organisms. Therefore the most important normal factor in determining the
intestinal flora in health is the chemical composition of the ingested
foods.
The nature of the dominant organisms which develop in diets rich in
carbohydrates varies with the carbohydrate itself. In all ordinary diets
there are (1) starches—forms not readily fermentable, and (2) sugars—
which are largely absorbed from the higher levels of the small
intestine, leaving residual starches and proteins in relatively great
concentration in the lower levels. Therefore the obligate fermentative
organisms are prominent only in the higher levels, the facultative
appear in the intermediate places, and the obligate proteolytic
organisms in the lower intestines. This accounts in a measure for the
great increase of lower intestinal disturbances in omnivores. Complete
proteins resist putrefaction, but the products of protein digestion and
of the intestinal secretions constitute the main substrata for
putrefactive bacteria. Animal protein develops more active proteolytic
bacteria than vegetable protein, which accounts for the greater
predominance of putrefactive infections in carnivores than in omnivores.
There are two important factors to consider in discussing the influence
of diet on intestinal bacteria: (1) The substitution of types, which
frequently follows a monotonous diet, and (2) the change in metabolism
of existing types of bacteria when dietary conditions are such that the
intestinal medium at one or another level fluctuates in its content of
usable carbohydrate and other nutrient. The nature and extent of these
modifications and their effects upon the host vary greatly, not only
qualitatively but quantitatively. An invasion of the tract by exogenous
bacteria, as the dysentery bacillus, cholera, typhoid, etc., in food or
water may lead to a more or less pronounced replacement of some of the
normal intestinal types by these alien organisms, and to the production
of disease.
The importance of all the foregoing facts concerning the changes in the
food, in the intestinal cultural substrata and in the advent of new
kinds of organisms was emphatically demonstrated in the marked fall in
gastrointestinal diseases in carnivores after proper screening of meats.
The simple protection of the food given to these animals eliminated the
air bacteria which, entering from dust and flies, alter the chemistry of
the meat before consumption or change the flora of the intestine after
consumption. Normal organisms, or types indistinguishable from them, may
multiply, through unusual conditions, extend their normal habitat, and
eventually lead to abnormal reactions detrimental to the host. These
facts throw considerable light on the site and character of
gastrointestinal lesions found in various orders, a subject to be
discussed more fully later.
There are many intestinal disturbances of unknown causation, in some of
which bacteria presumably play a secondary part. The primary disturbance
is due to the products resulting from the action of bacteria upon food.
Many toxic bodies are produced either before or after ingestion by the
bacterial decomposition of carbohydrate, fat or protein, independent of
any actual infection. The symptoms arising from bacterial decomposition
of foods depend largely on the organism concerned and vary from a mild
intoxication to a severe toxemia.
RELATION OF DIETARY GROUPS TO AUTOPSY DIAGNOSES.
Analysis of the autopsies on file from sole point of view of dietary
habits of the animals gives rather interesting groupings of disease
states, which apparently and, in some cases definitely, emphasize the
relationship between food, metabolism and disease. (Table 19.)
From this table a few facts stand out prominently. It is definitely
shown that both birds and mammals on a diet of mixed animal and plant
tissue show a low percentage of disease in the gastrointestinal tube,
liver, pancreas and kidney. The mammals on this diet give the highest
figures for anemias and degenerative osseous conditions. Birds on this
diet show very little osteomalacia, but a fair amount of anemia.
Possibly this may be accounted for by the fact that all of them pick
gravel and may be able from this to supply some of the inorganic
deficiency. Carnivorous birds and mammals, on the other hand, show an
exceedingly large assortment of gastrointestinal disorders, diseases of
the accessory glands of digestion, and of the kidneys. Disorders of the
thyroid gland are almost entirely confined to carnivorous mammals—7.5
per cent., compared to 0.25 per cent. in all other orders. Gout, while
common among birds, was not present in any mammalian autopsy, while
arthritis in mammals reached its highest record among grass- and grain-
eating herbivora. The percentage of rickets was highest in the young
carnivores (2.6 carnivores as against .4 per cent. in all other
mammals), and was very rare among all birds.
The succulent vegetable diet was lowest in its relation to degenerative
visceral disorders and highest in acute gastritis; the latter fact was
probably due to the fermentation of soft moist food that requires rather
a long time for its primary digestion. This type of food has also a high
and easily available sugar content which makes it a very favorable
medium for many of the fermentative types of bacteria. Most of the
lesions in this group were around the pylorus and upper duodenum.
TABLE 19.
_An Analysis of the Pathological Findings Described in the 5,365 Autopsies from
the Point of View only of the Dietary Habits of the Animals. The Percentage
Results Represent the Proportionate Number of Cases of Each Pathological Lesion
Found in the Entire Group of Animals on Each Special Diet without Reference to
Zoological Orders._
═════════════════╤═══════════════════════════════╤═══════════════════════════════
Disease states │ Mammalia 1860 │ Aves 3505
─────────────────┼──────┬───────┬────────────────┼──────┬───────┬────────────────
„ │Omniv-│Carniv-│ Herbivora │Omniv-│Carniv-│ Herbivora
│ ora │ ora │ │ ora │ ora │
─────────────────┼──────┼───────┼──────────┬─────┼──────┼───────┼─────┬──────────
„ │ „ │ „ │Succulent │Grain│ „ │ „ │Seeds│Succulent
│ │ │Vegetables│ │ │ │ │Vegetables
─────────────────┼──────┼───────┼──────────┼─────┼──────┼───────┼─────┼──────────
Malnutrition │ .1│ 1.6│ .6│ 2.2│ .05│ .4│ .1│
Food Poisoning │ .3│ │ │ 2.5│ .05│ .2│ .08│
Acute Gastritis │ 3.2│ 6.3│ 9.3│ 3.1│ .9│ 2.│ 1.3│ 13.5
Acute Duodenitis │ .5│ .3│ │ .5│ .1│ 1.4│ 1.2│ 5.4
Acute Enteritis │ 2.5│ 3.4│ 3.│ 3.1│ 7.│ 1.│ 8.│ 5.4
Acute │ 26.3│ 53.2│ 19.9│ 29.2│ 25.3│ 38.6│ 35.6│ 64.8
Gastroenteritis│ │ │ │ │ │ │ │
Chronic Gastritis│ 1.1│ 6.│ 2.│ .8│ .2│ 1.4│ .3│ 5.4
Chronic Enteritis│ 2.│ 5.6│ 3.│ 2.2│ 1.1│ 3.3│ 1.3│ 13.5
Colitis │ 1.9│ │ │ │ │ │ │
Acute │ .1│ 2.2│ 1.│ 3.1│ .4│ .6│ .08│
Pancreatitis │ │ │ │ │ │ │ │
Chronic │ .5│ 1.7│ │ │ .2│ 1.2│ .5│
Pancreatitis │ │ │ │ │ │ │ │
Acute Liver │ .8│ 1.3│ .3│ 1.4│ 4.2│ 2.8│ 2.5│ 2.7
Disease │ │ │ │ │ │ │ │
Chronic Liver │ 3.│ 6.3│ 3.3│ 6.│ 1.1│ 2.5│ 1.6│ 13.5
Disease │ │ │ │ │ │ │ │
Acute Nephritis │ 9.1│ 12.2│ 12.7│ 12.4│ 5.1│ 6.7│ 4.1│ 8.1
Chronic Nephritis│ 4.5│ 11.6│ 6.7│ 7.8│ 2.9│ 6.7│ 2.1│ 13.5
Myocardial │ .1│ .34│ │ 1.1│ .3│ 2.│ .4│ 8.1
Degeneration │ │ │ │ │ │ │ │
Arterial Disease │ .1│ 3.1│ .3│ 2.2│ .3│ 3.1│ .66│ 1.8
Anemia pernicious│ .3│ .32│ │ │ │ │ │
Anemia secondary │ 4.2│ .32│ 1.2│ 1.5│ 1.1│ 2.5│ 1.5│
Thyroid Disease │ │ 7.5│ .3│ .7│ .3│ .2│ .3│
Adrenal Disease │ 1.6│ 1.3│ .3│ 1.5│ │ │ .08│
Diabetes │ │ .2│ │ │ │ │ │
Osteomalacia │ 5.2│ .4│ 2.3│ .2│ .1│ .6│ 2.8│
Osteitis │ .6│ │ │ │ │ │ │
deformans │ │ │ │ │ │ │ │
Arthritis │ │ .3│ .3│ 2.2│ │ .2│ .08│
Rickets │ .1│ 2.6│ .6│ .7│ │ │ .08│
Gout │ │ │ │ │ │ .4│ .08│
Sore Eyes │ │ .3│ │ .2│ .1│ │ .3│
Malignancy │ .05│ .9│ .6│ │ .05│ │ .6│
Tuberculosis │ 32.6│ 3.5│ 4.5│ 9.6│ 12.│ 1.7│ 17.2│ 5.7
─────────────────┴──────┴───────┴──────────┴─────┴──────┴───────┴─────┴──────────
Overeating is a factor that must be borne in mind when considering the
hay- and grass-eating herbivora. Packing of the rumen is a not
infrequent discovery. This condition is also found in certain seed-
eating birds. As a supply of food is constantly at the disposal of these
animals and exercise is prevented by captivity, continuous eating
becomes their principal diversion. In this group also food poisoning was
highest, a condition which may be due to (1) spoiled food, (2) poisonous
substances in the foods, (3) fermentation of grass foods (spoiled hay or
musty fodder). Malnutrition also, is higher than with any other diet,
due probably to the somewhat meagre nutritious value of the food. This
group also shows a high percentage of acute pancreatitis, degeneration
of the liver, myocardium and arteries. Arthritis was present in this
group 2.2 per cent., against 0.2 per cent. in all other groups.
A study of Table 19 demands a constant recollection of the morphology of
the tract involved and its main points of vulnerability, the bacteria
capable of living on the particular type of food or its constituents and
the by-products produced during the digestion and absorption of these
foods. Not one of these factors can be ignored in evaluating the
influence of diet, which to be correct must supply elements in
proportions that are chemically available for body needs (for instance,
Von Wendt[59] found that more iron was required if the diet was
deficient in calcium). These proportions must be worked out by carefully
combined chemical and biological experiments.
MALNUTRITION.
There was one omnivorous beast, a Hamadryas Baboon, which represented
the only true case of starvation, probably induced by nostalgia, as it
never ate after coming into the Garden. Thirty cases of partial
starvation or malnutrition are listed in our records, the majority among
the rarer specimens, ten carnivorous, seven herbivorous and one
omnivorous mammals, ten carnivorous and two seed-eating birds, due
possibly to inappropriate diet or to some unknown factor that rendered
the diet inadequate. At the autopsy nothing was found to account for
death except the draining of all storage supplies.
STARVATION.
The reports of studies conducted during long laboratory fasts have been
among the most valuable records for the understanding of the chemical
requirements of diet and of the close chemical interrelationship
existing between the different food factors. In absolute starvation life
is very short, primarily because water is necessary for respiration, for
dissolving products of metabolism and for preventing changes in
digestive intestinal secretions. The amount of water needed varies with
different species of animals. If the water is supplied, the organism is
enabled to maintain its energy for continued existence from the
destruction of its own tissues. The length of life depends upon the
amount of protein ingested before the fast commenced, and the amount of
stored fat and glycogen, especially that stored in the liver. The
mechanism of the results is similar. The animal body uses first its
available glucose, and when this is partially exhausted burns its stored
fat and protein. The fat combustion is usually defective, ketone bodies
appearing in the urine in large quantities. The change from fat to
protein metabolism accounts for the premortal rise in metabolism which
occurs usually a few days before death. The chemical composition and
corpuscular richness of the blood is tenaciously preserved; glucose and
protein concentration are practically normal up to the day of death.
There is at times a slight increase in globulins and always an increase
in fat due to its transportation from storage depots. The cause of death
is primarily due to loss of substance in organs necessary to life and to
an acid intoxication.
Wasting occurs first in stored substances, fat, glycogen, etc., then in
the least used organs. The bones usually show some rarefication. The
animal, as a rule, dies from acid intoxication before atrophy of the
organs is marked.
In the wild, when animals are forced to seek their food with the
expenditure of much energy and where feasts are often followed by fasts,
this using up of storage supplies cannot help being a factor in
preserving the integrity of the storage and eliminative organs. In
captivity this cannot occur. Food is supplied regularly, exercise is
lacking, consequently overloading and disease of storage and eliminative
organs is more or less constant—a situation very marked in the
Carnivora.
TABLE 20.
_Detailed Analysis of the Various Diets Used at the Philadelphia Garden
on Basis of 100 Grams of Mixed Food._
═════════════╤══════════════╤═════════════╤══════════════╤═════════════
│ Omnivora │ Carnivora │ Herbivora │ Herbivora
│ │ │ Succulent │ Coarse Food
│ │ │ Vegetables │
─────────────┼───────┬──────┼──────┬──────┼───────┬──────┼──────┬──────
„ │Mammals│Birds │ Meat │ Fish │Mammals│Birds │ Hay │ Seed
│ │ │ │ │ │ │ Food │ Food
─────────────┼───────┼──────┼──────┼──────┼───────┼──────┼──────┼──────
Protein │ 14.3│ 11.5│ 15.6│ 17.2│ 6.1│ 3.2│ 6.4│ 7.1
Fat │ 9.5│ 7.2│ 18.8│ .3│ 2.6│ .5│ 2.2│ 1.3
Carbohydrate │ 26.7│ 41.2│ │ │ 18.5│ 25.7│ 35.9│ 51.2
Calcium │ .034│ .068│ .058│ .109│ .067│ .025│ .071│ .044
Magnesium │ .058│ .093│ .118│ .133│ .164│ .119│ .289│ .16
Potassium │ .497│ .713│ 1.694│ 1.671│ .538│ .242│ .644│ .324
Sodium │ .103│ .284│ .421│ .373│ .08│ .291│ .089│ .261
Phosphorus │ .263│ .484│ 1.078│ 1.148│ .556│ .342│ .692│ .458
Chlorine │ .117│ .377│ .378│ .528│ .038│ .044│ .073│ .063
Sulphur │ .338│ .486│ 1.146│ 1.119│ .134│ .125│ .217│ .163
Iron │ .0032│ .0063│ .015│ .0055│ .0018│ .0012│ .0022│ .0012
─────────────┴───────┴──────┴──────┴──────┴───────┴──────┴──────┴──────
A further study of Table 19 in the light of the finer analysis of the
ingredients of the diets, shown in Table 20, explains, at least in part,
the high percentage of certain types of disease in relation to
particular diets.
In the food of the first group, the omnivorous mammals, there is a
moderately increased carbohydrate content and an unevenly balanced
inorganic content, the last being the factor most at fault. The calcium
and phosphorus are both so low that at the best the animal could only be
in equilibrium, while any drain of the fixed bases would sooner or later
have to be replenished from the calcium and phosphorus storage depots,
the bones. Osteomalacia is most marked in the Cebidæ, monkeys whose diet
is even lower in these same elements: calcium .025, phosphorus .116, and
iron .0008 per 100 grams of food. The inorganic composition of all
animals is grossly similar; the typical digestion developed from the
habitual diet of the animal explains the more apparent changes and
variations in their reactions to certain deprivations.
IRREGULARITIES OF INORGANIC METABOLISM.
Twelve essential elements are present in the body, namely: carbon,
nitrogen, hydrogen, oxygen, phosphorus, calcium, sulphur, sodium,
chlorine, potassium, iron, magnesium. Of these, five are furnished by
the protein molecule and three of the five are duplicated in the fats
and carbohydrates; the remaining seven must be present in the mineral
ash. These elements functionate in three ways, (1) as constituents of
bone, (2) as essential elements of organic compounds, (3) as soluble
salts in body fluids. Chlorine, sodium, sulphur are supplied in
sufficient quantity with most diets. In the case of chlorine, marked
differences exist between the herbivores and carnivores. The meat-eating
mammals easily acquire sufficient sodium chloride from the flesh and
blood of their victims, while the herbivores on the other hand, find in
their vegetable food large amounts of potassium and very little sodium
or chlorine which must therefore be acquired separately. Both omnivores
and herbivores crave salt, probably because this large potassium content
of vegetable food tends to increase the sodium elimination. A
deprivation of salt always leads to a distaste for foods rich in
potassium. So far as is known excessive sodium stimulates protein
catabolism, and through the overstimulation of the digestive tract, may
interfere with the absorption of food.
Sulphur is largely taken into the body in organic combination with the
protein, (a very little inorganic sulphur appears in the drinking water)
therefore if the protein requirements are adequate the sulphur will
usually be adequate.
Magnesium is abundant in meat and most plant tissues; so that except in
diets of highly refined foods, it is more often excessive than
deficient.
The other elements, calcium, phosphorus and iron are frequently
insufficient, especially for animals on omnivorous diet (cf. Table 20).
Phosphorus enters into every living cell, and in cases of starvation is
excreted up to the last. It is involved in practically all the cell
functions. In the body it is present (1) as an inorganic compound in the
bone tissues and blood where it helps to maintain neutrality, (2) as
phosphorus-containing protein, phosphatids and phosphoric esters of a
carbohydrate, all closely associated with the cell and its nucleus. In
foods, phosphorus occurs in the same positions, that is, inorganically
or combined with protein, fat or carbohydrate. It is not entirely proved
but is very probable that the phosphorus in organic combination has the
greater metabolic value, inasmuch as there is greater storage of
nitrogen and stimulation of tissue growth on foods containing
phosphorized proteins, fats, etc. It has been shown, however, that the
animal body can satisfactorily supply its phosphorus requirements by
inorganic phosphates. The omnivorous diet, even the widely varied diet
of man, is very often deficient in phosphorus, a fact which becomes very
important when we consider that the omnivorous diet produces many acid
residues which must be neutralized, and that phosphorus is largely
responsible for the maintenance of tissue neutrality. Voit showed that
the phosphates excreted during starvation were withdrawn from the bones;
and there is much proof that during the daily metabolism a certain
slight movement of phosphorus takes place. The metabolized phosphorus is
excreted by carnivores practically from the kidney alone; by herbivores
almost entirely through the intestinal wall, while in the omnivores it
is excreted by kidney and intestinal tract. Whether these facts have any
real influence on the phosphorus need of different types is not
altogether determined.
Calcium also enters into many of the essential functions of life,
coagulation of the blood, contractility of the heart, etc. Omnivorous
diet is usually deficient in this element, which is very irregularly
distributed both in animal bodies and plants. Insufficient amounts lead
to deprivation of body tissues and to the production of osteomalacia-
like conditions. Voit produced marked thinning of the skull bones and
sternum by a diet poor in calcium. Steenbok and his associates had the
same results in cattle by feeding “shorts” a diet rich in magnesium.
Etienne[60] showed that an excess of magnesium in an otherwise well
balanced food caused a continual loss of calcium. Adults stand a
deprivation of calcium much better than children or young animals. They
often show no symptoms and retain a normal blood content as the losses
from the blood and soft tissues are promptly replaced from the bones.
Sooner or later all these animals show weakness and flexibility of the
bones. Osteomalacia occurred in 5.2 per cent. of the animals on an
omnivorous diet, that is this number showed gross evidence of absorption
of bone salts. This condition occurring in man and the lower animals is
a generalized softening of adult bones that were at one time normally
calcified. Three clinical varieties are recognized in man: a mild form
seen in pregnant, puerperal and lactating women, a senile form in which
the lesions are usually limited to the pelvis, and a severe progressive
form encountered in both sexes and at any age. This last form ends in
marasmus. Its chemical characteristic is a loss of calcium and
phosphorus with retention of sulphur and magnesium.
The progressive type has occurred very frequently among the Cebidæ whose
diet on careful examination, showed a protein content low in quantity,
poor in quality, and especially deficient in the phosphorus-containing
proteins and total fat. The carbohydrate was high. The ash was small in
amount and predominatingly acid. The daily ration often showed only an
unweighable trace of calcium, phosphorus or iron. Sodium, potassium,
sulphur and magnesium, on the contrary, were present in amounts
sufficient for equilibrium or in excess. The Vitamines A.B.C. were
present but were not always correctly proportioned. The fat soluble A
was low and in some daily rations was entirely lacking.
Diet has at various times been proposed as at least one factor in the
production of this condition, a premise that has gained considerable
weight through the increase in the number of cases, both in man and in
the domesticated animals, reported from the war-famine district of
Central Europe where the dietary was restricted and unbalanced. It has
been shown that when calcium is low in the diet, the amount excreted
materially exceeds the intake. Benedict[61] has further shown that even
during absolute fasts calcium is excreted. The requirements of this
element for man have been fairly well worked out, but for animals we
have no standards. Still it seems certain from the foregoing
observations that storage supplies are called upon very early in cases
of deprivation, while in pregnancy and lactation when the calcium
requirements are greatly increased, a reason is found for a higher
incidence of osteomalacia, Steenbok and Hart[62] have shown that the
skeletons of cows and goats gave evidence of a drain of inorganic salts
during the production of milk unless the calcium and phosphorus of the
diet were liberally supplied. In osteomalacia it would seem that
inefficient diet, if not the cause, was at least a very potent factor in
pathogenesis. The disturbance of the calcium-phosphorus-metabolism may
be due to the deprivation of the alkaline salts as in the famine
osteomalacia, to a drain from the alkaline storage of the body
associated with an inefficient diet as in the osteomalacia of pregnancy
and lactation or to the combined action of a diet faulty in more than
its salt content, which by the production of acid in its oxidation and
by favoring the development of acid-forming bacteria, causes a drain of
the body alkali for neutralization of the acid; or it may possibly be
due to a combination of all these factors acting through their influence
on the ductless glands.
Paget’s disease or Osteitis Deformans is a chronic constitutional
process which usually involves all the bones of the adult skeleton.
DaCosta[63] believed it to be a disorder of bone metabolism probably
dependent upon absence or perversion of some internal secretion. We have
had the unique opportunity of observing three cases of this disease in
Cebidæ, the family of monkeys which has presented the highest incidence
of osteomalacia. The experience is all the more interesting because of
the typical picture presented by the specimens, and of the absence of
references in the literature on the subject, to the occurrence of the
malady in wild animals. The interesting point about these cases lies in
the fact that the disease appeared in all three only after lime water
was added to the diet to supply the deficiency of calcium.
Search for literary record of the disease brought to light a case in a
horse that Barthelemy[64] described, but this involved the epiphyses of
the bone while osteitis deformans is confined as a rule to the
diaphyses. This case was probably more closely allied to osteitis
fibrosa cystica. Goldman[65] described examples in fowls and Rossweg[66]
refers to specimens in domestic goats and monkeys. Many of these cases
first come under observation through fractures, an accident common to
osteomalacia, but very rare in well developed osteitis deformans. The
diet of our monkeys was exceeding low in those substances essential to
bone development. Sherman[67] has shown that the calcium balance is
regulated to a certain extent by the calcium ingested, and that when the
diet is poor in this element, the output materially exceeds the intake,
a condition which is definitely changed when the animal is put on a diet
high in calcium.
So far as we could find there are no recorded studies of the mineral
metabolism of beginning cases of Paget’s disease. It seems possible from
the study of osteomalacia that the low mineral and otherwise faulty
diet, added to the symptoms produced by that diet might so disturb the
chemical equilibrium, directly through the neurotrophic mechanism or
through the perversion of the ductless glands, that the mere addition of
the lime water might entirely change the pathological picture. This is
in accord with the histology where the initial lesion is resorption of
bone followed by irregular proliferation. It is also in accord with the
probable chemistry of calcification. These animals all showed a lowered
carbon-dioxide-carrying-power of the blood, and therefore lowered
ability to carry calcium in solution. It is possible that Paget’s
disease is but a stage in a deficiency disease, a faulty reparative
response through a disordered neurotrophic mechanism, or through a
perversion of the glands governing calcium metabolism. Such perversion
could be caused by an improperly balanced diet, or by the addition of an
excess of calcium to the diet of an animal whose body fluids were unable
by reason of previous faulty diet or other disorder, to hold it in
solution. In young animals the calcium demands are much higher than in
adults, a need met in the high calcium content of breast milk, a content
in excess of almost every other food, but apparently just sufficient to
maintain calcium equilibrium. After it is weaned the young animal
frequently shows disorders of its inorganic metabolism. Herter estimated
that a child should store at least 0.1 gram of calcium daily and he
described many cases of arrested bone development occurring during
infancy and early childhood, because of an inefficient assimilation of
calcium. One case, probably of this character, was found in a Hamadryas
Baboon (_Papio hamadryas_) a typical example of infantilism. The animal
was an adult male about half the size of an adult female. His skin was
fine and more delicate than normal, the bones were small and slender,
contour of body was that of a young animal, genitalia were imperfectly
developed, thyroid gland apparently normal, gastrointestinal tract
atrophic, associated was a slight arthritis, portal cirrhosis of liver
and diffuse nephritis.
First among the results of inorganic insufficiency in youth stands
Rickets. This disease occurs in children starting usually at about the
sixth month and continuing with irregular remissions for several years.
The bone changes, which are the most prominent, are always associated
with more or less severe anemia, a general lowered resistance and flabby
musculature. The excretion of calcium is very high in the feces and low
in the urine. There is a frequent negative calcium balance dependent
upon the great loss in the feces. Healing is preceded by a
hyperretention of calcium and a relative increase in the urinary
calcium. The excessive loss of calcium in the feces is not brought about
through the agency of fats because fat could only remove calcium as
insoluble soaps and these are not at all increased. This fact
contradicts the idea of fat starvation as a cause of rickets. Howland
and Kramer found that the blood in active rickets had a normal or
slightly lowered calcium content, but a regularly reduced phosphorus
content. The latter deficiency was extreme at times. They ascribe to
this deficiency the failure of the bones to calcify. It can be readily
understood that a decrease of phosphorus in the blood would render
difficult the precipitation of calcium phosphate.
Recently two series of studies, the first by Pappenheimer, Zucher and
McCann and the second by Shipley, McCollum, Park and Simonds have shown
that rats fed on a diet low in calcium but with a sufficient amount of
fat soluble vitamine and phosphorus develop a bone condition with many
fundamental resemblances to rickets. They were also able to produce the
condition with an excess of calcium and deficiency of phosphorus. On the
first diet, the condition differs from rickets in that the arrangement
of the proliferating zone of cartilage cells is maintained and the
evidence of bone resorption in the diaphyses is excessive. A diet
deficient in both calcium and phosphorus leads to an atypical rickets.
In the animals autopsied at this Garden rickets occurred very much more
frequently in the flesh-eaters than in any of the other dietary groups.
On closer analysis it was found that rickets in almost every case
appeared in the carnivores which did not receive bones as a part of the
food. Rickets occurred frequently in the omnivorous macaques which
however did not show osteomalacia, although they belong to the same
dietary group as the Cebidæ. The reason they did not suffer the latter
disease while adult but had rachitic young is probably due to the fact
that this monkey group, which breeds best in our Garden, receives in
addition to the diet given to Cebidæ one raw egg. This increased the
calcium content of their food more nearly to the requirements of these
mammals. These monkeys also have mouth sacs, which enable them to
acquire more food per kilo of body weight than the smaller Cebidæ which
are not so advantageously equipped. The food even in the amounts
consumed by the macaques is low in calcium, phosphorus and iron. It is
very possible that there are enough of these ingredients present as a
rule, to maintain the animal in organic equilibrium, during normal life,
and possibly even enough to supply the needs of the embryo but not
sufficient to maintain the young during the period of lactation. A few
macaques dying during the delivery of young showed slight osteomalacic
changes in the pelvis. This was notably present in one described in
detail by E. A. Schumann.
The calcium requirements of the female are always much increased during
pregnancy and lactation due to the withdrawal from the mother to meet
the needs of the embryo and nursling. Forbes and Beegle[68] found that
lactating animals made heavy drains on their storage calcium even when
the diet was liberal and the animal was storing nitrogen.
Iron is the essential element of hemoglobin and chromatin—the body
constituent most directly concerned with the process of oxidation,
secretion, reproduction and development. The iron of the food is
absorbed from the small intestines, enters the circulation through the
lymphatics, is deposited in the liver, spleen, and bone marrow and
eliminated through the intestinal walls. There is very little iron
reserve in the adult body; and as a result any failure of the intake to
equal the output causes an immediate reduction of the hemoglobin. Voit
found that the iron eliminated in the feces of starving dogs, or dogs on
a diet low in iron comes from the body through the intestinal walls.
Medicinal iron stimulates the production of hemoglobin and red blood
cells but whether it is directly employed in the production of
hemoglobins has not been proved. Undoubtedly most of the extra iron
given with the food passes through the alimentary tract without being
absorbed or metabolized. The greater the amount of iron in the food, the
greater the influence of the inorganic iron. Anemia occurred in all the
animals we examined at least four times as frequently in omnivorous as
in all the other dietary groups, a fact probably explained by the low
content of iron and calcium in this diet. Both Von Wendt[69] and
Sherman[70] demonstrated that larger amounts of iron were required to
maintain the iron equilibrium when the amount of calcium was low.
Herter has shown that many anemias are associated with intestinal
putrefaction. The carnivores, however, on a diet that putrefies very
easily and on one in which the iron content is apparently of distinctly
lower nutritive value than that of the iron found in milk, eggs and
vegetables, presented an anemic incidence of only 0.32 per cent. This is
probably due to the excellent hygienic care of the meat foods and to the
morphology of the carnivorous intestinal tract, which is short, straight
and fashioned for quick elimination. The cases of anemia steadily
increase among the animals as the conformation of the tract approaches
the omnivorous type with the longer and wider hind-gut.
Herbivora, obtaining their iron from vegetable sources, are much less
liable to blood disorders. The iron needs of the female are greater than
those of the male because of the drains of pregnancy and lactation.
Young animals demand more iron than adults. All exclusively breast-
feeding animals have a considerable storage of iron in the body at
birth, while those that eat food immediately have no such supply.
Bunge’s[71] experiments showed that breast-fed animals contained about
six times as much iron as the milk that nourished them. The iron content
of all these animals is highest at birth, remains constant during the
suckling period and then rapidly decreases to the adult standard. After
this level is reached the iron metabolized must be supplied from the
food if the hemoglobin is to be spared.
The functions of all these inorganic substances are intimately
interrelated and in places interchangeable. Calcium is capable of
correcting disturbances of inorganic equilibrium in the animal body
whatever the direction of the deviation from the normal may be. These
interrelationships are most involved in the maintenance of body
neutrality. The normal processes of metabolism involve a continual
production of carbonic, phosphoric and sulphuric acid which must be
immediately disposed of if the neutrality of the body is to be
permanent.
The factors involved in this are carbonates, phosphates, ammonia and
proteins. Carbon dioxide is the chief excretory product but is at the
same time a normal constituent of the blood and as such, is an important
factor in this physicochemical regulation. There is a tendency for the
respiratory mechanism to hold its carbon dioxide tension nearly
constant. Late investigations have shown that lowering of this tension
is an early sign of beginning acidosis. When food such as protein, is
taken in excess the strongly acid residues are neutralized by the sodium
and potassium carbonates which are eliminated with a corresponding loss
of sodium and potassium. The carbon dioxide tension diminishes, 37.2 per
cent. on a high protein as against 43.3 per cent. on a vegetable diet.
If this excess is long continued, the result may be, and often is, an
increased elimination of the base-forming elements which if not made
good tends to diminish the body’s reserve alkalinity. A diet with a
preponderance of basic elements leads to an alkaline urine with an
increased uric acid solvency and an increased carbon dioxide tension and
reserve alkalinity. A diet with a preponderance in the acid-forming
elements, on the contrary, leads to an increased urinary acidity and
urinary ammonia, decreased ability to dissolve uric acid and lowered
carbon dioxide tension and alkaline reserve.
DEFICIENCIES OF VITAMINES.
Recent investigations have shown that diets furnishing sufficient
amounts of protein, fat, carbohydrate and inorganic salts may yet prove
inadequate for growth or even for maintenance. Hopkins,[72] feeding rats
on purified food mixture was unable to obtain any growth until he added
small quantities of milk or of the ether-soluble portion of milk but
with this addition growth progressed in the normal manner, but it was
out of all proportion to the energy or protein value of the addition.
Five substances of this character, called by Funk[73] Vitamines, have
been described, two of which have definitely established a place as
essential food factors. According to him, pellagra, rickets, scurvy and
beriberi are the result of a lack of these unidentified but specific and
indispensable food complexes.
The first vitamine isolated was the fat soluble A, an adequate supply of
which is necessary, not only because of its stimulating growth
properties, but because its absence produces a serious condition of the
eyes and, at times, marasmus leading to death. Xerophthalmia is a common
condition in animals on experimental diets. The eyes are swollen, the
cornea inflamed and often opaque while blindness and death invariably
occur unless the dietary error is corrected. McCollum[74] rescued
animals almost at the point of death by butter or other fat rich in this
vitamine. Opacities of the cornea are often seen in the animals in this
and other gardens among ungulates—hay-eating mammals; four advanced
cases were found, three in seed-eating birds and one in a fox on a diet
made up solely of horse muscle. The quantity of vitamine A present in
muscle, hay and seeds is very small. It is supplied in largest amounts
in milk, eggs, glandular organs and leaves, substances which were very
low or absent in the diet of all the affected animals. This
xerophthalmia has been reported in man on several occasions, especially
by Hrdlicka[75] in American Indians, by Mori[76] in 1400 Japanese during
a period of food shortage (this epidemic was cured by the addition of
chicken livers to the diet), by Bloch[77] in forty-seven children of
Copenhagen fed on a fat free milk who were cured by the administration
of cod liver oil. The disease is not however a fat starvation, as it is
entirely uninfluenced by vegetable fats which do not contain this
vitamine.
Beriberi is an established deficiency disease, frequently seen among the
poorer classes of the Orient whose diet is limited to polished rice and
fish. It has appeared in Labrador coincident with the excessive use of
bolted flour. A similar condition has been induced in pigs and cattle by
a diet made up of an excess of cotton seed meal and tankage. Two forms
of the disease are described: (1) acute or wet, characterized by marked
edema, ascites, hydropericardium, hydrothorax, edema of the lungs, and a
congestion of the spleen, liver, kidney, and heart muscle, (2) chronic
or dry, characterized by polyneuritis. The disease was first produced
experimentally in pigeons by Eijkman[78] in 1897 by means of a diet of
polished rice. The paralysis appeared in 2–3 weeks after the diet was
initiated. Fraser and Stanton[79] in 1907, found that it could be cured
by an alcoholic extract of rice polishings. Funk[80] later determined
the vitamine character of this extract. In pigeons and fowls
experimental feeding usually results in the chronic or polyneuritic
form, expressed by a typical degenerative inflammatory condition of the
peripheral nerves. In pigs, on the contrary, Rommel and Vedder[81]
produced both types, though the acute or wet beriberi appeared more
frequently. In rats the same deficiency causes multiple hemorrhages in
the cerebellum and midbrain followed by a degeneration of the associated
nervous structures. It is possible that the pathology following a lack
of the vitamine B or in fact any of the vitamines will vary with the
different species or with varying demands of different individuals. This
antineuritic vitamine affects more than the nervous system, and it is
possible that all vitamines may have wider effects than are at present
described.
Scurvy was the first condition to call attention to diet as a cause of
disease. It occurs in man when deprived of fresh vegetables. That faulty
diet was in some way the cause of scurvy has been known for many years,
but only since 1905 has there been any systematic attempt to determine
the peculiar value of the curative foods. At this time Theobald
Smith[82] called attention to a disease suggestive of scurvy which
developed in guinea-pigs fed on a diet of oatmeal. This observation was
confirmed by Holst and Frölich[83] who stated that the disease could be
prevented by the addition of fresh milk or cabbage, because in these
foods there was present an antiscorbutic or C vitamine. This
unidentified substance was easily destroyed or diminished by heat or an
alkaline medium. It was found in rather large amounts in succulent
vegetables and fruits. McCollum[84] and his coworkers showed that the
oat kernel was low in inorganic salts and vitamine A and poor in the
quality of its protein; but with these faults corrected it proved to be
a complete food for rats. McCollum also found that scurvy developed more
readily in animals if the physical properties of the diet favored
constipation. He was able to delay the onset of the disease in guinea-
pigs for a considerable period by the addition of mineral oil which has
no food value, or phenolphthalein, a cathartic. At the same time,
Jackson and Moore,[85] found the cecum of all guinea-pigs dying of
scurvy, packed with putrefying feces. They were able to produce a mild
type of the disease by the injection of the diplococci isolated from the
swollen joints.
From these observations it seems safe to conclude that scurvy may not be
purely a deficiency disease, or even a simple dietary one, although the
presence of a vitamine influence is not excluded; but it is probably the
result of a bacterial invasion of tissues debilitated by a faulty diet
and by the toxins produced by the putrefactive bacteria developing in a
diet unsuited to the anatomical demands of the alimentary tract. This
theory receives support from the fact that pasteurization destroys all
aciduric bacteria, allowing only the spore-forming putrefactors to
develop; and from the fact that scurvy develops more frequently in
children on stale pasteurized than on stale raw or boiled milk. In this
Garden no suggestion of scurvy has been noted.
Pellagra is very definitely a disease of poverty endemic for years among
the poor, especially in the mountains of Northern Italy. It has been
under observation in the United States since 1907. So far as is known no
cases have been observed among animals. Opinions differ as to the rôle
of diet in the etiology but the results of recent studies seem to show
that uncomplicated cases of average severity clear up entirely on a diet
rich in animal protein. No vitamine deficiency has so far been
determined. Wilson’s careful studies of the diets known to have produced
the condition show that the etiological factor lies in a deficiency of
the protein molecule. The results of Goldberger[86] corroborate this
fact, and he concludes from his latest studies that “the dominating rôle
of diet in the prevention and causation of pellagra is referable
primarily to the character of the protein supply or to the specific
quality of the aminoacid makeup of the protein supply.” Just what
aminoacid or combination of aminoacids it is, has not been determined,
nor has the possibility of a vitamine alone or in combination with the
aminoacid factor been absolutely excluded.
The principal influence of the omnivorous diet is toward those
degenerations arising primarily from imbalances in the inorganic makeup,
or to insufficiencies of certain necessary factors. The vitamine
deficiencies are markedly less prevalent in animals than in man whose
food is less often consumed in its natural state. It is now known that
much of the injury and loss of nutritive value in foods is produced by
the processes involved in preparation, preservation, refinement and
storage. Whenever the choice of food is not restricted, vitamine
deficiencies do not occur. The vitamine requirements probably differ in
different species and in individuals from the same species according to
their environmental and individual variations. It is very possible that
if the diet is low in vitamine content there may arise conditions of
relative deficiencies; and McCarrison has shown that a vitamine
deficiency associated with a high fat or carbohydrate content may
disturb the balance of the endocrine glands. It is however to the
inorganic content of the omnivorous food that most of the disturbances
peculiar to this diet are to be assigned.
With the flesh eating animals and birds the records present a very
different picture. Disorders of the digestive tube, of the storage
organs, of the organs of elimination and of the endocrine glands
predominate. Their diet is low in carbohydrates and, at times, in fats
and very high in protein. Bone supplies the inorganic salts, which in
this Garden is fed only to the larger mammals. The carnivorous birds get
their inorganic supply from mice which are eaten entire. The carnivores
are as a rule large and are given to active fighting or to long flights.
In the wild, very probably there are long periods between feasts, while
in captivity the food is always plentiful and regularly supplied. This
regularity added to the lack of exercise, particularly among the larger
animals, must lead to excessive demands upon the storage and eliminating
organs. Storage is always promoted by rest and liberal diet, and cleared
away by exercise and starvation. The life of these birds and mammals,
moreover favors inactivity of the bowels, which, together with the
highly putrefactive diet adds another serious factor to a problem which
in gardens is almost insurmountable.
IRREGULARITIES OF CARBOHYDRATE METABOLISM.
The carbohydrates are derived from the glucose and glycogen of the meat
and from the protein molecule. They are absolutely less than in the diet
of herbivores but become a factor in the disorders of this group because
of the lack of exercise and the regularity of feeding. In digestion the
carbohydrate becomes available for absorption and bacterial growth in
the upper small intestine and appears on the other side of the
intestinal wall as blood glucose in which form it is burned for energy
or stored as glycogen for the future maintenance of the blood glucose.
The blood of different animals has a glucose concentration between
0.05–0.1 which for each species is quite constant, as it is regulated by
the coadaptation of four factors: combustion, fermentation of glycogen,
formation of fat, and elimination from the kidney. In excessive feeding
the amount needed for energy is burned, the remainder is stored in the
liver up to its capacity, then in the muscles and other cells, after
which fat is formed and all further excess is eliminated by the kidney.
Overfeeding causes an immediate overloading of the oxidative mechanism
with symptoms of gastric disorder, achylia, and at times acid
fermentation with irritation of the stomach walls and the development of
bacteria in the organ. This is frequently followed by glycosuria,
several types of which are described: (1) associated with an increased
concentration of glucose following excessive ingestion exceeding the
normal glycogenic function of the liver, a form common among the
Herbivora, (2) that due to a reduction of the glycogenic function of the
liver, (3) that associated with disease of the ductless glands in which
the resulting glycosuria probably depends upon the influence of these
glands upon the pancreas, (4) that dependent upon the defect of
glycolysis or to an overstocked liver seen in gout, obesity or
hypertrophic cirrhosis, and (5) renal glycosuria due to a lowering of
the renal threshold and usually associated with gout, arteriosclerosis
or chronic nephritis; this last is best explained on the ground of
increased renal permeability. Normally when the blood sugar
concentration rises above a certain level the elimination _via_ the
kidney begins and continues until the blood has again reached its normal
concentration. The relation of the kidney to glucose concentration is
not constant and variation is always toward the side of lesser
elimination while the kidneys become accustomed to the higher level.
Diabetes, a disease of the islands of Langerhans in the pancreas, is
essentially a disturbance of sugar metabolism always associated with an
exaggerated and defective fat and protein combustion. It is not only
that the diabetic has lost the faculty of combustion but these
abnormalities all establish states of intoxication to which the diabetic
must sooner or later succumb. Among lower animals the disease is rare.
Dogs are most frequently affected (about 1 in 12,000 deaths). It has
also been described in horses, cattle and monkeys. In our records there
was one case an Arctic fox (_Canis lagopus_) presenting a typical
picture. Degeneration of the islands of Langerhans was seen in three
other animals, but there was no other evidence of diabetes. This disease
is not due to diet but to the absence of a normal ferment
(pancreaticozymo-excitor) for one particular type of food.
IRREGULARITIES OF FAT METABOLISM.
Disorders of fat metabolism are very rare among lower animals
notwithstanding the fact that fat even in the carnivorous diet,
represents about 13 per cent. of the whole intake. It plays two
important rôles in the body, storage for energy reserve, and as a most
essential structure in cellular protoplasm, in which position it joins
with protein in complex combinations of still unknown composition which
present to a striking degree the phenomenon of absorption. Very marked
biological differences exist in the value of fats from different
sources, due to the presence or absence of vitamines. The body fat is
derived from the fat of the diet or is synthesized from glucose. The
former is specific to the fat consumed while the latter is specific to
the animal. In omnivores the type depends upon the varying extent to
which animal fats enter the diet, in carnivores it depends almost
entirely on the fat intake, while in the herbivores practically all the
fat is synthesized from the carbohydrate. On digestion, fat splits,
yielding a glycerol and fatty acid which are collected in the lymph
spaces of the intestinal mucosa, there changing to some complex
combination which is not only soluble but diffusible.
Fatty infiltration and fatty degeneration are conditions of much
pathological interest and of great frequency in captive animals. The
researches of Mansfield[87] have thrown considerable light upon these
conditions. He found that the total fat content in cases of most marked
degeneration was normal or reduced. The proportion of fat free from
protein was increased and the firmly bound fat decreased. This increase
is due to neutral fat brought from without the organ by the blood when
for any cause the oxidative powers are decreased, and setting free of
the previously invisible intercellular fat and lipoids, which are
normally present in the cells, by autolytic or physicochemical changes.
This condition is pretty evenly distributed among the dietary groups,
the liver being most commonly involved. The hepatic cells are easily
degenerated by the toxins or other harmful substances passing through
the organ and become passive and unable to throw off or to utilize the
deposited fat. In all probability the same general situation occurs in
the atheromatous changes in arteriosclerosis which on this diet shows a
high incidence. The causative agent is probably some poisonous
substance, possibly a protein degradation product, indol, pressor
substance, acting on the intima over long periods, or at irregular but
often repeated periods causing first destruction then fat accumulation.
It is also possible that it may be caused by repeated absorption of some
sensitizing protein. Arteriosclerosis in these animals is often closely
associated with nephritis.
Obesity may result from excessive ingestion of food in individuals whose
habits are sedentary and whose digestions are active or it may come from
an inherent abnormality of metabolism dependent upon ductless gland
disease. It is very common in castrated animals. The obesity of
overeating is always of milder type than that associated with endocrine
disturbance.
So far as is known there are two main disorders of fat metabolism—the
failure of the diabetic to form fat from glucose, and acidosis, the
inability of the organism to burn fat beyond betaoxybutyric acid,
acetoacetic acid, or acetone. The symptoms are unsteadiness of gait,
stupor, coma, air hunger, in all of which the essential features are due
to the impoverishment of the body in available bases. In infants this
frequently follows an excessive fat diet. It is also common in
starvation due to the deprivation of sugar. It is associated with
phosphorus poisoning, narcosis, carcinoma, liver disease, inanition,
etc. It has been produced experimentally by the administration of acids
or by foods deprived of their bases. The excess of acid in the body
whether produced in the body or introduced from without must be
neutralized in part by the ammonia manufactured in the ultimate
metabolic transformation of the protein and by the alkaline salts of the
blood and tissues. When alkali is reduced the carbon dioxide accumulates
in the tissues, blocking oxidation. The urine immediately shows an
increase of ammonium salts, a decrease of the urea and an increase in
the output of sodium, potassium, calcium and magnesium, which last two
are drawn from the bones.
Symptoms do not arise until the fixed alkalies are exhausted; and they
are immediately relieved by the administration of alkalies, except in
those cases of starvation where the administration of sugar and the
subsequent sparing of the fats relieves the situation. In herbivores,
acidosis does not follow starvation, but, on the other hand, it is
markedly easier to excite it in herbivores than in carnivores whose
heavy protein diet produces more ammonia, which better enables the
animals to protect their fixed alkalies. The acid intoxication of
infections arises from different causes and is dependent on the
intensity of the type of infection; but ultimately it also depends upon
the depletion of the fixed alkalies.
IRREGULARITIES OF PROTEIN METABOLISM.
Fat and carbohydrate disturbances are not infrequent in carnivores, but
it is with the protein fraction of the diet that most of the trouble is
connected. Natural foods contain several proteins or groups of proteins,
whose biological adequacy depends upon their yield of aminoacid.
Experiment has shown that many proteins are entirely lacking in one or
more of these essential radicles; and no food can be adequate unless it
contains at least all the aminoacids that the individual animal is
unable to manufacture for itself. So far as is known, no animal can
produce in itself either lysin or tryptophane. Gliadin, the principal
protein of wheat and lacking in lysin, is unable to support growth even
when given in amounts sufficient to insure the storage of nitrogen, and
is associated with a diet adequate in all other factors. Absence of
tryptophane prevents not only growth but maintenance. Any of the
aminoacids, whose radicles are contained in tissue proteins, may
contribute to the maintenance of adult equilibrium; but no growth occurs
unless all the necessary groups are present. Except in laboratories,
diets are never made up of isolated proteins, but they are often
composed of proteins derived from one plant and are often deficient.
McCollum and his associates in their studies showed that while there
were pronounced differences in the composition of many foods used by men
and animals not only in their protein content but in water, fats,
carbohydrates, etc., yet in the combinations found even in rather
restricted diets, the errors, as a rule, corrected each other.
During digestion the protein molecule is broken down into the component
aminoacids which are absorbed and synthesized in the intestinal walls,
and appear on the other side as the specific blood protein, which serves
as the substrate for the anabolism of all the special tissue proteins.
Excessive protein is stored to a slight extent as aminoacid for the
future maintenance of the blood protein, the integrity of which is
tenaciously protected during hibernations, sexual migrations, and even
during starvation. The animal body tends to adjust its nitrogen
metabolism to its nitrogen supply; the adjustment requires an
appreciable amount of time. A diet changed to a lower nitrogen level
results in a continued loss of nitrogen, increased combustion of fats
and carbohydrates. The animal makes no apparent effort to reëstablish
equilibrium, and sooner or later digestive disturbances and loss of
strength occur.
If, on the contrary, the protein is steadily increased after an animal
has established equilibrium, the nitrogen metabolism increases and the
level of nitrogen equilibrium rises to higher and higher levels. There
is, at the same time, a lowering of the fat combustion, an increase in
the respiratory quotient and in the heat production. The excess protein
must be split, deaminated, burned and eliminated. Fifty-five per cent.
of the intake is converted into glucose which is burned and the excess
stored as glycogen. The sulphuric acid formed during the protein
cleavage is neutralized by the body alkalies. In these cases the liver
is often congested and enlarged. The urine shows excess of urea and
ammonia. At times the excess, being so great that it cannot be absorbed,
undergoes chemical and bacterial decomposition which causes digestive
disturbances, torpor and constipation.
The organisms associated with protein food are usually the putrefactive
types which break the protein molecule into the aromatic bodies,
phenols, indolacetic acid, indolpropionic acid, skatol, etc. These
bodies on absorption are believed to give rise to hypertrophy of the
adrenal, interstitial changes in the kidney, and arteriosclerosis.
Another group of substances, pressor bases and amines, are manufactured
by certain anaerobes acting on proteins. These, when fed by mouth, are
detoxicated by the liver cells, but when formed below the portal
circulation, give rise to anaphylactic phenomena—urticaria, etc. Certain
other organisms give rise to soluble toxins as in botulism and
thyrotoxicon poisoning. All these types of toxins will destroy if they
act acutely in sufficient concentration; or as is more common, if they
act persistently over long periods, or at oft recurring intervals they
will cause serious injury to the tissues coming in contact with them,
and have a part in the production of cirrhosis of the liver, chronic
nephritis, myocarditis, arteriosclerosis, etc.
All foods have a limit beyond which they are excreted untouched or
imperfectly oxidized. Many of these partial oxidation products of
protein are in themselves toxic and may also be a source of these
degenerative organ conditions. The pathological material studied by us
showed a marked decrease in gastrointestinal diseases in close
association with the more hygienic care of the meat foods.
Always associated with the protein foods are the nucleoprotein
complexes, which are split by both bacteria and digestive juices into
globulins and nucleic acid, and then through the agency of a special
enzyme, into purin bases and uric acid, in which forms they are excreted
in the urine and feces. The oxidation of purins is never complete.
Gout, representing the pathology of purin metabolism, is a paroxysmal
inflammatory disturbance, due to the deposition of sodium urates in the
joints or in the internal organs, usually accompanied by a fibrosis
especially in the liver, kidney, arteries, etc. The disease occurs
almost exclusively in birds. Isolated cases have been described in dogs,
horses and hogs, but among lower animals it is undoubtedly very rare. In
birds it is most frequent in the carnivores—4 per cent., as against 0.02
per cent. in all other groups. It is higher in fish-eating birds than
among the flesh-eaters. The avian gout is usually of the visceral type
and was most marked in its distribution over the organs in the Anseres
and Psittaci, birds whose diet apparently is not unduly heavy in
nucleoproteins, but whose tract approaches the carnivorous type. The
only arthritic cases occurred in Boat-billed herons (_Cancroma
cochlearia_), fish-eaters. Our records show examples in Accipitres,
Galli and Columbæ, although the number of cases in the last order were
few and slight in extent. This disease stands in close relation to diet,
as it develops on generous protein food, high in nucleoprotein or
hypoxanthin, especially if this be associated with restricted activity.
The carnivorous mammals lead in the disease of the thyroid glands.
Thyroid disease occurs among the birds, but is equally distributed among
the dietary groups. Thyroid activity has a marked influence on
metabolism probably through the influence of the iodine-containing
protein of its secretion. There are some experimental evidences in favor
of a detoxicating function of the thyroid, of which the following are
quoted: (1) The effects of thyroidectomy are most marked in the
carnivores; Herbivora are often capable of several years of life without
thyroid tissue; (2) administration of meat to thyroidectomized omnivores
or herbivores caused a marked increase in all symptoms. The importance
of the relation of the meat diet, detoxication and thyroid disease
receives considerable confirmation from the fact that among the 1,860
mammalian postmortems thyroid disease occurred in 2.6 per cent. of all
mammals, 94.9 per cent. of which were found in flesh eating varieties.
Wells[88] suggested that possibly this could be interpreted as an
indication that toxic materials found in the meat in the intestinal
tract were, under normal conditions, detoxicated by the thyroid. Against
a local neutralization, however, is the improvement following the
administration of dried thyroid substance. The function is either
neutralization of toxic substances or the stimulating action on
intracellular metabolism, both of which might be called into play by an
excessive protein diet.
THE CARNIVOROUS DIET.
The pathology of the more prominent diseases developed in carnivores
points at least to diet as a predisposing or determining factor. This
diet is very high in a distinctly putrefactive protein and yields
products, chemical and bacterial, which are toxic and which give rise to
acute or more often chronic diseases of the alimentary tract and its
adnexa. By reason of the amount ingested, excessive because of lack of
exercise, there is a severe tax on the storage organs and on the
detoxicating glands, as the liver and thyroid. The constant absorption
of these toxic substances gives rise to chronic degenerative or fibrotic
changes in the organs through which they pass: liver, kidneys, arteries,
heart. In birds the degenerative diseases are even more marked than in
mammals on the same diet. The ultimate fault of this diet, especially
for mammals and birds with restricted activity, lies in the production
of toxic bodies, produced either in the incomplete degradation or
oxidation of the protein molecule or as the result of bacterial action
on the protein molecule, a poisonous quality which is probably enhanced
by the chemical changes occurring while the digested protein is passing
through the intestinal mucosa. Garden conditions are such that these
factors are almost unsurmountable unless the substitution of vegetable
protein could be accomplished. Failure is often caused by limited
feeding to carnivores of muscle and bones, whereas they should be
supplied with glandular organs and blood.
THE HERBIVOROUS DIET.
Herbivorous diet must be divided into two groups, (1) that composed of
succulent vegetables, and (2) of grasses, grains and seeds. In the first
group there is an apparent variation in the results found in mammals and
birds. In both there is a marked decrease in the chronic degenerative
pathology. In both, acute gastritis is more prominent, far outstripping
the incidence of this condition in other classes.
This diet yields a large and quickly available amount of carbohydrate
which in conjunction with the moisture, heat and bacteria which are
unavoidably associated with raw vegetables, makes an ideal situation for
infection. These foods carry many saprophytic bacteria, moulds, etc. In
birds the conditions are aggravated by the injuries that may occur from
the sharp objects picked up with the gravel. The incidence of acute
infection is higher among birds than among mammals of this group, and
often there is involvement of the whole tract. The explanation of the
other pathological findings occurring among birds must be found in the
frequently repeated low grade infections which result finally in the
production of chronic lesions in the digestive tract, liver, pancreas
and kidney. Toxins as an etiological factor cannot be altogether
excluded, but as a rule they are not important because the by-products
of vegetables are distinctly less toxic than those derived from animal
sources. Arteriosclerosis is much less frequent and less intensive in
herbivorous birds than among the carnivorous, probably because of
differences in the concentration and character of toxins in the two
groups.
SOFT HERBIVOROUS DIET.
The diet of succulent vegetables is composed of tubers, edible roots and
leaves. The tubers and edible roots are high in water and carbohydrate
and poor in the amount and quality of the protein, most of which is not
even a true protein but a mixture of aminoacids. The leaves, on the
contrary, are rich in organic ash, especially calcium, sodium, chlorine,
and fat soluble A vitamine, and as a rule contain a good quality of
protein. They often, however, contain injurious substances. This diet,
while measurably less nutritious than that of the carnivores, can
satisfactorily nourish many animals with an extensive intestinal tract
during growth and even throughout their entire life, but proves entirely
inadequate when fed to an omnivorous tract.
SEED DIET.
Closely allied in general character to the diet of succulent vegetables
are the seed diets, eaten only by birds and having no parallel among
mammalian foods. All seeds, in contradistinction to tubers, contain true
proteins which, however, are of poor quality because of the deficiencies
in the aminoacid content. They are as a rule low in the fat vitamines
and in the amount of calcium, sodium and chlorine carried. In three
pathological conditions only do these birds show any oversusceptibility:
(1) Sore eyes, (2) acute enteritis, (3) osteomalacia. Sore eyes were
frequently noted in this group. The lesions were very like those
described in animals deprived of the fat vitamine, which was present in
this food in very small amounts or entirely absent, thus giving a very
plausible explanation of this condition, especially as in some of the
cases no other cause could be found. Gastric disease of any type is rare
in this group because the food at the gastric stage is highly resistant
to bacterial action. In the duodenum, however, the conditions are early
changed because the bacteria carried with the food through the stomach
become active in the presence of available carbohydrate and protein
decomposition products.
Osteomalacia is confined almost as exclusively to the seed-eating birds
as it was to the omnivorous mammals, and it is also associated with the
same deficiencies, calcium and phosphorus (cf. Tables 19 and 20). It is
also interesting to note that these two diets, the omnivorous and seeds,
yield the greatest number of cases of tuberculosis. Mammals showed 32.6
per cent., as against 5.8 per cent. in all the other dietary groups, an
observation which becomes more striking when man is added to the
omnivorous group. Seed-eating birds showed 17.2 per cent., as against
6.4 per cent. in other groups. In both diets the fat, fat vitamine and
inorganic salts, especially the calcium, are deficient in amount. In the
wild, birds vary their diet of seeds with insects, worms, soft fruits
and the tender shoots of plants, and at the same time they increase
their inorganic intake by the minerals picked up with the gravel and
from the water which has penetrated the soil.
GRAIN AND GRASS DIET.
The hay-eating animals constitute a large and well studied group—
including practically all the domestic varieties. Table 19 shows that
these animals yield the greatest number of cases of malnutrition, food
poisoning, acute pancreatitis, acute degenerative conditions of liver
and myocardium.
Recent literature describes many cases of osteomalacia, especially among
horses and cows, in the famine districts of Europe. In our collection of
1,860 postmortems only one case was found, that of an Isabelline gazelle
(_Gazella isabella_), a hay-eating animal, and in this case it was
secondary to infection.
Arthritis, occurring in 3.4 per cent. of all the autopsies, was almost
entirely confined to the hay-eating animals. The literature describes
many cases of arthritis almost entirely confined to ungulates, of which
many were associated with calving and subsequent infection.
Bacteriological researches have found it most often associated with
streptococci, staphylococci, or Bact. perfringens, organisms that
require a certain amount of carbohydrate for their proper development.
The relation of diet to this condition probably lies only in the fact
that it provides an excessive carbohydrate substrate suitable for the
optimum development of these organisms. Folin and Bergland, noting
glycoresis in Herbivora, thought that it represented the absorption and
excretion of unusable carbohydrate, present in grains, vegetables,
fruits, etc., and that it was sharply separated from the main
carbohydrate metabolism. These products were absorbed from the blood
exactly as they were ingested like lactose, dextrose, etc., are
absorbed, but do not enter into the economy although they might cause
disorders, especially forms of arthritis.
The grain foods are composed largely of carbohydrates (principally in
the form of cellulose and starch) small amounts of protein and little or
no fat. They have a very low nutritive index so that large amounts must
be consumed to supply adequate calories. This food is constantly
present, and during the enforced idleness of captivity is almost
continuously eaten. Despite these facts, however, malnutrition is
present in 2.2 per cent. of the animals on this food. Associated with
the plentiful food and lack of exercise are overeating and pica.
Overfilled stomachs occurred thirty-four times. They were limited to
these mammals and to the seed-eating birds whose environmental
conditions are practically the same. Pica or excessive appetite for
abnormal food, is also more frequent in these groups, but is usually
associated with badly balanced diets, and thus represents an effort on
the part of the animal to supply its own deficiency. It is present in
osteomalacic monkeys and has been reported in cattle from regions where
osteomalacia is common and following crop failures where the rations are
restricted. In cattle it very often accompanies food poisoning,
especially that produced by ingestion of peat hay.
Disturbance of the alimentary tract and its adnexa occurs in two forms:
(1) Infection which is quite common and involves the duodenum, pancreas
and liver, and (2) toxic. Compared with other diets alimentary disorders
are not frequent among grain feeders, despite the ease with which grass
foods ferment and the great variety of organisms found in them such as
moulds (aspergillus), Bact. coli, paratyphosus, enteritidis,
suipestifer, oidium lactis, etc. Few bacteria can attack whole protein,
cellulose or starch, and the decomposition products, peptone, glucose,
etc., are not available in any quantity until the lower stomach and
duodenum are reached. The inflammation of the alimentary tracts of these
animals is confined to the fourth stomach and duodenum, with, in many
cases, extension to liver and pancreas.
Acute and chronic degenerative changes occur very frequently, and as a
rule are the result primarily of absorbed toxins. After ingestion of new
hay this often appears. The toxic substance probably is a terpinol
ester, cumarin, which is produced by an enzyme in the cut grass.
The result is a gastroenteritis with jaundice, thirst and marked
flatulence. It is very probable that many of the gastrointestinal and
degenerative lesions are the result of the combined action of toxin and
bacteria.
FOOD POISONING.
Food poisoning occurs in all diets, but especially among the grass-
eating mammals. To-day under the general heading of food poisoning are
included those cases due to (1) some injurious substance inherent in the
food itself, true food poisoning, (2) those due to toxic substances
liberated or produced in food contaminated by parasites or bacteria, (3)
those due to bacteria that are carried by food and develop into true
infection after ingestion. Most of the cases of meat poisoning described
in literature undoubtedly belong to this third class, _i.e._, flesh is
infected during the life of the animal or during its preparation for
food and the virus develops in the host after ingestion. A fourth and
more rare class of food poisoning is due to the condition of the
individual consuming the food-protein sensitization.
Injurious constituents of normal flesh foods are very uncommon. There
are a few poisonous fish, notably the balloon, puffer, and Fuga fish of
Japan, which when eaten give rise to cholera-like conditions ending in
convulsions and paralysis. A marked intoxication has been described in
dogs which have fed upon the Greenland shark. Some fish are poisonous at
certain periods as spawning season, the poison then being confined to
the roe. Still others are harmless unless rendered toxic by some
injurious food. This poisoning of muscle meats is seen in quail and
partridges fed on mountain laurel, in some fish after consuming certain
marine plants, and in cattle poisoned by amanita.
The most common sources of poisoning are spoiled meat and flesh of
diseased animals, both of which are serious factors in the production of
the gastrointestinal disorders of omnivores and carnivores. Practically
all the reports of meat poisoning from the literature have been traced
to the use of raw or insufficiently cooked flesh, and have yielded on
bacteriologic examination _Bact. paratyphosus_, _Bact. enteritidis_,
_Bact. suipestifer_, _Bact. coli_, or _Bact. proteus_.
The bacteria may produce toxin in the food previous to ingestion causing
in the host only a severe intoxication. This is the situation developed
after eating sturgeon infected with _Bact. piscidus agilis_, an organism
which manufactures a highly poisonous alkaloid. A similar intoxication
follows the ingestion of potatoes infected with _Bact. proteus_ or
containing the poisonous alkaloid, solanin, which is produced in
diseased and sprouting potatoes. Other examples of this are (1)
ergotism—due to an infection of rye and wild grasses with _Claviceps
purpurea_ which produces three poisonous bodies, ergotinic acid, which
is not poisonous when taken into the stomach, sphacetinic acid and
cornutin which act on the nervous system, brain, cord, vagus and
vasomotor centre giving rise to toxic polyneuritis, and (2) favus, an
acute febrile anemia with jaundice and hemoglobinuria probably due to a
bacterial infection or fungus growth of the bean. Infected food may also
produce soluble heatresisting toxins that produce immediate symptoms and
increase the animal’s susceptibility to infection. This is the more
common finding in cases of poisoning with milk and milk products. Non-
pathogenic saprophytes carried in milk produce (1) a poison closely
allied to tyrotoxicon, (2) a toxalbumin which in itself causes serious
disturbances. Botulism, also probably of this group, is a disease
initiated by a toxin elaborated by _Bact. botulinus_ acting on a
protein. There is, however, some evidence that _Bact. botulinus_ can
also establish a real infection.
The toxemias from food infected with bacteria may not occur until the
food is ingested or the bacteria implanted. This result occurs in
infections with _Bact. bovis morbificans_, Gärtner’s bacillus, etc., or
after the feeding of meat from animals infected with _Bact.
paratyphosus_ and _enteritidis_.
The plant poisons are more frequently due to inherent injurious
substances, although even among them, bacterial and fungus diseases play
an important rôle. Among the 16,673 plants indigenous to North America,
almost 500 are more or less poisonous and about 30 are of great economic
importance. The toxic factor may be confined to the leaf, seed or root,
but more often it is associated with all parts of the plant. Through the
efforts of the Department of Agriculture a more or less complete list of
the plants implicated in the poisoning of stock has been compiled. This
list includes the following: _Amanita muscaria_; _A. phalloides_;
_Veratrum viride_; _Phytolacca decandra_; _Agrostemma githago_;
_Delphinium_, 25 varieties; _Astragalus mollissimus_; _Aragallus
lambertii_; _Crotalaria sagittalis_; _Euphorbia lathyris_; _E.
marginata_; _Rhus radicans_; _R. diversiloba_; _R. vernix_; _Aesculus
pavia_; _A. hippocastanum_; _A. glabra_; _A. Californica_; _Cicuta
maculata_; _C. vagans_; _Conium maculatum_; _Kalmia latifolia_; _K.
augustifolia_; _Leucothöe catesbaei_; _Rhododendron maximum_; _Pieris
mariana_; _Datura stramonium_; _Solanum nigrum_; _S. dulcamara_;
_Helenium autumnale_; _Asclepias pumila_; _A. verticullata_; _A.
galoides_; _A. mexicana_; _A. eriocarpa_; _A. speciosa_; _A. fremonti_;
_Eupatorium agertoides_; _E. urticarfolium_; _Isocoma wrightii_;
_Daubentonia longifolia_; _Senecio jacobia burchelli latifolius_.[89]
Some of these as the Amanita are only occasional sources of disaster,
but as they frequently involve man they are important. The _Amanita
muscaria_ symptoms appear very soon after eating the fungus and consist
of a deepening stupor. _A. phalloides_, on the contrary, starts with
severe abdominal pain, cramps, discharges of blood and mucus and later
convulsions. The meat of animals dying from fungus poisoning is
distinctly poisonous. This transfer of poison to the muscles of the
animal partaking of these plants occurs also in poisoning with Kalmia.
The other plants of this list are closely associated with the grass
foods and are consumed usually when the food on a range is scarce. Some
groups as the Asclepias contain a distinct neurotoxin and give rise to a
condition known as trembles or staggers. It affects mostly cows and
sheep, causing staggering, trembling gait, bloating and salivation and
death with convulsions. There is marked congestion of alimentary tract,
liver and kidney. In the cerebrospinal axis there are marked changes in
the nerve cells of the medulla and spinal cord. The Purkinje cells show
the effect of extreme fatigue. Other plants causing stiffness or
weakness of the extremities, show on microscopic examination no definite
lesions in the cerebrospinal axis. Loco weed—_Astragalus mollissimus_
and _Aragallus lambertii_—causes maniacal disturbances but no gross
lesions. This weed in Colorado costs the state enormous amounts of money
yearly.
Helenium poisons domestic animals by means of a toxic glucoside,
dugaldin, which produces stiffness, salivation and nausea with mild
depression (“spewing sickness”). The alimentary tract shows severe
inflammation of the rumen and reticulum which may at times be
hemorrhagic. The liver usually presents an interstitial hepatitis. This
toxin is decidedly hemolytic. The effects of this plant are always
permanent, total recovery being very rare.
The larkspur (25 different varieties), on the contrary, shows prompt
recovery after treatment, but no establishment of toleration. These
plants give rise to nausea, vomiting and great agitation and destroy
many animals yearly. The poisons are included in four alkaloids, all
spinal cord depressants resembling aconite in general character.
These poisonous plants all produce more or less gastrointestinal
inflammation and practically all are destructive in their action on the
liver, pancreas and kidney. It is impossible to form even approximate
estimates of the damage done by them because of the general ignorance of
the subject. The Division of Botany has been collecting for the past few
years specific information concerning these plants, but the individual
plants are not equally poisonous, and all animals do not show the same
susceptibility to the poison. _Veratrum viride_, for instance, is eaten
with relish by sheep and elk and is decidedly toxic for the horse. In
many the toxic factor has not been isolated. Some, as Euphorbia, are
poisonous only when fed in honey derived from its flowers.
The influence of diet on the general health of animals is very far
reaching and very inclusive. Metabolic disturbances are undoubtedly at
times the result of unbalance—deficiencies on the one side, excesses on
the other, at times are probably much more the results of bacterial
invasions aided and abetted by the food administered, at still other
times are poisonous either in their own content or from the degradation
products resulting from digestion or bacterial decomposition.