Volume 30 | Issue 1
Article 3
1967
A Short History of Early Digestion Trials
D. Dale Gillette
Iowa State University
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Gillette, D. Dale (1967) "A Short History of Early Digestion Trials," Iowa State University Veterinarian: Vol. 30: Iss. 1, Article 3.
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A Short History of Early Digestion Trials t
by D. Dale Gillette, D.V.M., Ph.D.
Although Hippocrates (C.400 B.C.) ascribed certain qualities to food and founded a dietetics based on personal observations and the accumulated knowledge of
the era (8) and although Erasistratus of Julius at Alexandria (C.300 B.C.), "Father of
Physiology," traced hunger to an empty
stomach; little was done in actual trials to
determine the digestible nutrient value of
foods. The first trials apparently were
made by Francesco Redi (1626-1698) as
an experimental investigation of the grinding power of the gizzard of household
fowl. (17)
In this dawn of nutrition Albrecht Von
Haller (1708-1777), the most prominent
physiologist of the eighteenth century,
writes: "Receptum est in hominum opionione quod ossa animalibus subigantur; cum
Helmontianis olim sensit Boerhaavius; (5)
ut vero certior esset curam adhibiut, ut
observaret, quid cibis fieret in ventriculis
animalium valde cibos coquentium & experimento cognovit non subigi. Dedit cani
devoranda intestines animalium, famelicus
erat affatim deglutiit subegit minime &
per extremum intestinum pendula misere
post se traxit. Dedit famelico cani ossa
butyro inuncta, reddidit furfura, neque
quidquam dissolvit nisi quod in aqua dissolvi potest. Dedit carnes, reddidit fibras
carnis exsuccas. Dedit ligamenta, ea post
tridium nihil muetata egessit.":j: This was
.. Dr. Gillette is an Associate Professor in the Depart·
ment of Veterinary Physiology and Pharmacology,
Iowa. State University.
Issue, No.1, 1968
the first scientific investigation concerning
"Throw the poor dog a bone."
Rene Antoine Reaumer (1683-1757), a
French naturalist, gave two bones to a
bitch and found they had diminished in
bulk-and that several laminae were dissolved or removed. The bones were also
noted more flexible. He thus inferred the
bones were digested in part. This was only
part of a work he was carrying on with digestion trials. (16) In trying to find if the
cause of digestion was solutitm or trituration, he filled punctured metal tubes with
grain and postulated:
"Should these grains, after they have remained a certain time in the stomach be
broken down and decomposed we must assign a dissolving liquor as the cause of the
phaenomenom, since the sides of the metallic tubes must have been an insuperable
obstacle to the exertions of the gastric
muscles upon the contents; but if they
should be retrieved in a sound and entire
state, it must be acknowledged that in
these animals digestion does not depend
on a solvent, but on muscular action." He
fed the tubes filled with barley to various
t Some of this material is found in Fulton's writings on the history of physiology (4).
l "Established 1n human opinion is the digestion of
bones as declared by Helmont and Boerhaave; thereI contend it might be put to treatment; so it was observed how food fared in the belly of animals, food
well cooked and from experiments known not to be
broken up. A hungry dog was given animal intestines. he ate sufficiently. digested minimally and from
his anus a wretched hanging thing protruded. A hungry dog was given bones smeared with butter; he
voided a bran-like substance only a part of which
could be dissolved in water. Meat was given. given
back was stringly. flesh juice. Ligament was given
and after eating nothing was discharged."
11
gallinaceous birds and retrieved them with
the barley entire. Thus he concluded that
in those birds food was broken down not
by a solvent but by muscular action. He
supposed the gizzard stones necessary to
digestion.
By employing similar tubes filled with
grass and forced into sheep, Reaumer
found the grass undigested when he killed
the sheep or if the sheep were allowed to
void the tube. Thus he Dlaimed that digestion in sheep could not be effected by a
solvent.
Working with a large kite, a scavenger
bird, because of the periodical vomiting of
the bird he discovered several things. Most
important he noticed flesh was dissolved
according to the length of time in the body
and ascribed digestion to a ,dissolving process by the gastric juice. He also disclaimed
Dr. George Cheyne (1671-1743) of London
and Bath, who claimed that crows cannot
digest flesh of their own species, but vomit
it up. (3)
In 1760 a certain Mr. Gosse who had developed the ability to vomit at will merely
by swallowing air, started observations on
digestion. * He would eat essentially the
same supper upon "diverse occasions" and
after various lengths of time would vomit
it up and examine the results:
"Y2 hour: not much change, foods retained taste, milk curdled
1 hour: pulpy, well mixed with gastric
juice, no fermentation present,
foods retained taste except wine
which was much milder.
2 hour: very pulpy and only Y2 of the
food left."
Upon numerous trials he made up what
might be the first digestibility lists of food:
"I. Substances not digested or such as
were not digested in the usual time.
Animal foods: tendonous parts of
flesh, bone, fats, cooked egg white
Vegetable foods: nuts, seeds, oils,
dried grapes, skin of fresh grapes,
skin of stone fruits such as cherries and peaches, conserves of
oranges and citrons, capsule of apples and pears, cherry stones
* Certain sources were not available and could not
be verified. The author believes they are mentioned
by Spallanzani (19).
.
12
II. Substances less indigestible
Animal foods: pork, black-pudding,
egg yolk, egg fritters, fried eggs and
bacon
Vegetable foods: coarse salads, raw
vegetables, warm bread, figs,sometimes pastries, onions and leeks
(raw or cooked) fried foods were
worse.
III. Substances easily digestible
Animal foods: flesh of young animals and poultry, fresh eggs (uncooked) and milk, fish
Vegetable foods: leafy green vegetables, asparagus, boiled fruits with
sugar, meals of various grains especially without husks, bread,
boiled rapes, turnips and potatoes
IV. Substances facilitating digestion
sa:!t, spices, mustard, capers, wine,
cheese (espc. very old cheese), sugar, bitters
V. Substances retarding digestion
hot water, acids, astringents, oils
and employment after a meal."
In this era Dr. John Pringle (17071782), a professor at Edinburgh, and Dr.
David Macbride (1726-1778) of Dublin developed a theory that digestion was fermentation. (10,13) They based it upon experiments in which they mixed various foods
with water or saliva and kept them at
warm temperatures. They observed stages
of fermentation of food into a sweet substance. This they corollated with observations in their medical practices of swelling,
rarefaction, froth and air bubbles and
movement of intestines in people recently
dead. They theorized that food, excited by
warmth, old residue food, movement, gastric juice, and above all by saliva fermented into a sweet mild nutrient called
chyme.
John Hunter (1728-1793), F.Ro'S. and
Surgeon to St. George's Hospital, observed
that the stomach of a man who was accidentally killed when in perfect health and
just after a large meal, was dissolved away
at the great curvature. He saw this repeated several times. (7)
Edward Stevens of Edinburgh, employed for experimentation "an Hussar, a
man of weak understanding Who gained a
Iowa State University Veterinarian
miserable livelihood, by swallowing stones
for the amusement of the common people,
at the imminent hazard of his life." (20)
Dr. Stevens gave this man a two-compartmented silver sphere which was pierced
with needle sized holes. Voided in 21 hours
the 4y:! scruples of beef on one side was reduced to 3 scruples and the 5 scruples of
fish on the other was reduced to 3. The
residue was softened but had no disagreeable odor. He then made the holes in the
sphere much larger and introduced chewed
beef. The sphere was voided empty in 38
hours. He also observed that raw potatoes
and parsnips were dissolved, but that bone
was not. In an attempt to find effects of
gastric juice upon living material, he put
in live blood sucking leaches and earthworms-all were dissolved.
Unfortunately the Hussar left Edinburgh and Dr. Stevens continued the experiments with dogs and sheep. In dogs
he got similar results with ivory sphereshowever the spheres themselves were digested away after 3 repeated trials. He
found bone and fat to be dissolved away
in the dog, but cartilage was not. In sheep
he stated flesh was not digested, but that
turnips and potatoes were.
Dr. Stevens was most probably the first
to conduct digestion trials in vitro. Ripe
mutton placed in gastric juice dissolved
without putrefying, but the same placed
in water gave off a terrible stench. He concluded that digestion is the result of a
powerful ferment, which the vital principle keeps from digesting the stomach. (He
was familiar with the observations of John
Hunter.)
In 1784 Lazaro Spallanzani published
the results of significant experiments in
digestion. (19) He repeated the trials of
Reaumer and obtained the same results.
After using crop soaked grain and changing from perforated tubes to a perforated
sphere, he reluctantly concluded that the
gizzard triturated the food. Using bread
and flesh he sawall stages of digestion.
He found that complete digestion takes
about 5 hours. He correctly ascribed
slower digestion of larger hunks to their
relatively smaller surface area.
By observing how a fresh mammalian
Issue, No.1, 1968
stomach lining became moist again after
the surface was wiped dry, he concluded
that invisible glands secreted the gastric
juice.
He incubated mutton and wheat with
gastric juice and with water as a control.
He satisfied his critics that digestion and
putrefaction were indeed distinct processes. Spallanzani rejected the idea of fermentation being the basis of digestion because he did not find fermentation in animals freshly killed after being fed, but that
the food (flesh) had dissolved according to
the time it was in the animal. To test Boerhaaves ideas he fed intestine, tendons, ligaments, and bone to a dog. They were digested-but not completely and quite
slowly. Ascribes Boerhaaves mistake "perceiving some intestine which he had given
to a dog hanging out behind he concluded
that the animal could not digest such substances." Spallanzani had a great influence in wiping out fallacies in the areas of
his experiments.
During trials with membranous stomached animals (his classification-which
included most mammals) and with intermediate stomachs of crows and herons,
Spallanzani noticed the round worms had
resisted digestion. Attributed it to the acclimation by the worms and to preferential digestion by the stomach. (Whatever
that is?)
In ruminants he repeated the work of
Reaumer, but used larger tubes, 8" by 4",
and had to contrive what he called a hollow cane to force them down. (Was this
the first speculum?) He gave 6 tubes to a
sheep, fasted it 27 hours, killed it, and retrieved the tubes-no visible digestion.
Upon repeating and letting animal live 37
hours he found the tubes undigested in the
fourth stomach. Mter speculating on the
effects of rumination he put grass which
had been masticated by humans in the
tubes and found digestion had occurred.
"But as the stomachs of ruminating quadrupeds have no sensible triturating power
and the aliment requires trituration, nature has wisely provided for this by causing it to ascend in consequence of a gentle
stimulus to vomit, into the cavity of the
mouth where by means of rumination it
13
receives the necessary predisposition to be
digested by the gastric fluid."
After Spallanzani's contributions to digestion, trials came more frequently, but
not always more correctly. The first American contribution, a thesis on digestion in
1803, was from John R. Young, son of an
emigrant Irish physician. He convincingly
established the presence of an acid in the
living stomach in this thesis, excerpts of
which are quoted. "We were therefore,
iead at first to suppose, the acid was only
present when this viscus was in a morbid
state; but experiments proved to us the
contrary." ". ". the following day, I took
some meat on an empty stomach, in half
an hour afterwards, by irritating my
fauces, the meat was thrown up, and with
it some gastric fluid: Upon being tested,
an acid was very evidently present."
"But does the gastric fluid act upon them
before death? The following experiment
proved to us clearly it did not . . ."
"Two threads were tied around the forelegs of a live, and common sized spring
frog; its whole body, except the head and
forelegs was introduced into the stomach
of one of the large frogs . . . They were
put in a basin containing a little water,
whe.re they remained undisturbed for one
day and a half. The small frog upon being drawn out, was perfectly alive and its
whole body covered with gastric juice, and
not the least dissolved in any part."
Delabere Blaine asserted that digestion
in herbivores continues long after ingestion.* A. P. Wilson-Philip (1770-1847),
an erratic Scottish genius, said that the
layer of food next to the stomach wall is
digested first. (23) Roget Bridgewater considered blood and a chyme the ultimate
products of digestion and upon the basis of
a chemical analysis pronounced them identical in composition in the different animals. * Antonio Montegre (1779-1818)
considered saliva as the principal agent of
digestion. (11)
To point out the darkness still ahead, the
following concepts were taken' from Principles of Digestion 1841 by Andrew Combe,
'" Certain sources were not available and could not
be verified. The author believes they are mentioned
by Spallanzani (19).
14
M.D., Royal College of Physicians of Edinburgh:
1. Plants extracted all their nutrients
from the ground.
2. Necessities for digestion were gastric
juice, 98 0 F., and agitation.
3. Dogs fed only oil or sugar, diseased
and died-because of the insalubrity
of too condensed nutriment. (Bleeding,
emolients and laxatives were recommended for this condition.)
4. The process of digestion is a conversion of the food by the gastric juices to
chyme (chymification) Birle and pancreatic juice are incorporated into the
chyme and it separates into a milky
white fluid called chyle (chylification)
and a yellow residue. The yellow residue becomes mixed with waste thrown
off from the blood in the large intestine and becomes feces which is voided. The chyle is absorbed into the lacteals and goes thru lymph glands to
the thoracic duct and is emptied as
close to the heart as possible so that it
can be airified in the lungs as soon as
possible and hence changed into blood.
This change is sanquification or blood
making, thus "Properly considered respiration is completion of digestion"(a truly paradoxical statement). This
was the opinion of the man who in the
same volume published and commented upon the works of William Beaumont, an American Army Surgeon.
However, Combe admitted that the
facts were few and speculation much.
A better viewpoint can be found in the
works of Prout: (15)
"Besides the great utility of the saliva in
moistening the food, we cannot doubt that
it assists, and is even necessary to the full
completion of the succeeding digestive
process." "The agencies operating in digestion, and in the first stages of as simulation
are, in man, perhaps the same that exist
in all organized beings,"-"the saccharine
group, . . . to consist of carbon associated with water."-"Another well known
class of bodies-are those whose character
is oily."-"They are either composed of
olefiant gas and water, or have a reference
to that composition." -"but all of them (he
Iowa State University Veterinarian
is writing of albumens), including gelatine; differ from the oleaginous and saccharine principles, in this respect; that
they contain a fourth elementary principle,
namely, azote. Such are the three great
staminal principals from which aU organized bodies are essentially constituted.Moreover, these staminal principals, in all
their forms, are capable of readily passing
into one another, . . ." "-food must necessarily consist of one or more of the above
staminal principals."
"Water may constitute an essential element of a substance-in which case, the
water cannot be disunited without destroying the compound: or water may constitute an accidental ingredient."-"carbon,
water and similar bodies always enter into
combination, not as single molecules, but
as one supermolecule."
Prout had great insight, he is known for
his speculation that all atomic weights are
exact multiples of that of hydrogen or ha:lf
that of hydrogen. He also discovered the
stomach contains hydrochloric acid. (14)
A summary of thc facts obtained by William Beaumont's experiments with the gastric fistula in the side of Alexis St. Martin
from 1825 to 1834 is as follows: (2)
1. Digestion of meat in vitro occurs as
quickly as in the stomach.
2. Digestion occurred on the surface of
the food particles.
3. Heat seemed to be increased during
digestion.
4. Contact of food with gastric mucosa
stimulated flow of gastric juice.
5. Fasting gastric juice was described
as "It was clear and almost transparent; tasted a little saltish and acid,
when applied to the tongue, similar to
a thin mucilage of gum arabic, slightly acidulated with muriatic acid."
6. Difference in milk clotted with gastric
juice from that treated with acetic acid.
7. Failure of vegetable tissue to disappear as did meat.
8. Cold gastric juice had little activity.
9. "Oil is particularly hard on digestion."
10. Stomach has characteristic motions.
11. Hydrochloric and acetic acids do not
digest foods as does gastric juice.
Beaumont said "probably the gastric
Issue, No.1, 1968
JUlce contains some principles inappreciable to the senses."
After 1840 most of the significant experiments in digestion were carried out by
German workers. Amidst the flowering of
one of the great Germanic periods in chemistry, physics and physiology; experiment
stations were set up at Weende, Halle,
Mockern, Proskau, Bonn, Breslau, Vienna,
Hohenheim, Munster and Munich-dealing mainly with farm animals. Foods were
classified as albuminoids (proteins), fats
and carbohydrates (for quite a while,
though, carbohydrates were rather neglected). Animals were fed different rations, excreta were collected and analyzed. Pettenkofer constructed an elaborate respiration apparatus in Munich to
determine fat and water involved in respiration and perspiration. Mathematics
and a new knowledge of chemistry were
combined to give calculations of flesh, fat
and water gained or lost during feeding
trials. Digestibility and composition of
many foodstuffs were determined. Control groups were run. The term "Nutritive
Ratio" was coined.
This new knowledge plus the establishment of feeding standards were gathered
in Landwirtschaftliche Futterungslehre by
Prof. Emil V. Wolff, director of the Royal
Agriculture College at Hohenheim in 1874.
This very important work was translated
to English in 1895 and was the basis of
Feeds and Feeding first published in 1898
by W. A. Henry, Dean of Agriculture and
director of the Agricultural Experiment
Station, University of Wisconsin. His
book became the world famous Feeds and
Feeding by Morrison.
Armsby also reported extensively on
these experiments in his classical text on
animal nutrition. (1) Highlights of this era
(1850-1890) are presented below with certain more comprehensive references
(which were not available to the author).
Many individual works can be found in
the Zietshrift fur Biologie, founded in 1865
by Voit, Pettenkofer and Buhl.
REFERENCES
1. Arm.by, Henry Prentiss, The Principles of Animal Nutrition, N.Y., J. Wiley & Sons, 1903.
2. Beaumont, William, Experiments and Observa-
tion. on the Gastric Juice and the Physiology of
Digestion, Plattsburgh, N.Y., F. G. Allen, 1833.
15
EARLY INVESTIGATORS
Investigator
Pettenkofer
Major Place
Munich,
Gennany
Pertinent Work
Respiration appartus for
digestion trials and "respiratory quotient."
Voit (& Bischoff)
(1831-1908)
Munich,
Gennany
Respiratory apparatus. Fat
from fat-free meat. Nitrogen balance studies.
Lawes (& Gilbert)
(1814-1900)
Rothamsted,
.England
Composition of fattening
animals. Fat from carbohydrates.
9
Henneberg (& Stohman)
Weende
The more food the more converted to flesh.
6
Berlin
31.5% efficiency from food
26
Rubner
Munich
Caloric values of food
stuffs. Retacement of
nutrients or heat production.
18
Wolff
Hohenheim
Variable digesti:bility of
fodder.
24
(1818-1901)
(1825-1890)
Zunty (& Hagemann)
(1847-1920)
(1818-1896)
3. Cheyne, George, Essay on Regimen Together.
with· Five Discourse. Medical, Moral and Philosophical, London, 1739.
4. Fulton, John F. and Leonard Wilson, Selected
Readings in the HistoTY of Physiology, 2nd ed.,
Springfield. ,Charles ·C. Thomas, 1966.
5. Haller, Abrecht von, Praelectonis BoeThaavi ad
PTOPTia. Institutiones, Gottlnga, 1739-1744.
6. Henneberg, W. and Stohman, BeitTage ZUT BegTiindung einer Rationellen Fiitterung deT Wiederkaiier, ,Brunswick, 1860-1864.
7. Hunter, John, On the Digestion of the Stomach
after Death, in Philosophical Transactions, 1772.
8. Jones, W. H. C., HippocTatic Collection, Transl.
1923.
9. Lawes, John and J. Gilbert, Phil. Trans. II, 1859,
493.
10. Macbride, David, Experimental Essays on the
Fermentation of Alimentary Mixture, London,
1764.
11. Montegre, Antonio, Experiences de la Digestion
dan. I'Homme. Paris, 1814.
12. Pettenkofer, Max von and Carl von Voit• .Ueber
einem neuen Respirationsapparate, Munich, 1861.
13. Prin.8"le, John, ExpeTiments on Substances Resisting Putrefachon, London, 1750.
14, Prout, William, On the nature of the acid and
saline matters usually existing in the stomachs of
animals, Phil. Trans. 1.14, 1824.
15. Prout. William, ChemistTY, Meteorology, and the
Reference
to work.
12
21,22
Function of Digestion Considered with Reference
to NatuTal Theology, London. W. Pickering, 1834.
16. Reaumer, Rene Antoine, Sur la Digestion, Mem,
Acad. Roy. Sci., Paris, 1752.
17. Redi. Francesco, Osservazioni Intomo agli Animali
Villenti. Firenze, Italy, 1684.
18. Rubner, Max. Ges. d. Energie VerM. b. d. Erniihrung, Munich, 1902.
19. Spallanzani, Lazaro, Dissertations Relative to the
Natural History of AnimalB, Transl. J. Murray,
London, 1784.
20. Stevens. Edward. Experiment Concerning Digestion, (an Inaugural thesis dissertation), Edinburgh. 1777.
21. Voit, Carl von and 'Bischoff, Die Gesetze der ETniihrung des Fleischfressers, Leipzig, 1860.
22. Voit, Carl von, Ueber die TheOTien der Emiihrung den Tierischen OTganismen, Munich. 1868.
23. Wilson-Philip, A. P., in various articles found in
Transactions of the Royal Society, c. 1830.
24. Wolff, EmU von, Anleitung ZUT Chemischen Untersuchunq Landwertschaftlich Wichtiger Sfoffe,
4th ed. Stuttgart, 1899.
25. Young. J. R., An Experimental Inquiry into the
PTinciples of NutTition, and the Digestive Process, Philadelphia, Eaken & Mecum, 1803. Reprinted by University of Illinois Press, Urbana,
1959.
26. Zuntz, Nathan and O. Hagemann, Untersuchungen iiber den Stoffwechsel des Pferdes bei
Ruhe und ATbeit, Berlin, 1898.
A Purse-string Suture Technique for Retention Coxofemoral Luxations
(Continued from page 6)
Journal of South African Veterinary
REFERENCES
1. American Veterinary Publications, Inc., Canine
Surgery, First Archibald Edition, p, 898-913, 1965.
2. Campbell, J. R.. Lawson, D. D. and Wyburn, R.S.,
Coxofemoral Luxations in the Dog, Veterinary
Record 77: p. 1173-1177, October, 1965.
3. DeAngelis, M., and Hohn, R. B.hVentral Approach
to Excision Arthroplasty of t e Femoral Head,
Journal of the American Veterinary Medical
Asso. 152: p. 135-138, Jan. 15, 1968.
4. DeVita. J. A.• A Method. of Pinning for Chronic
Dislocation of the Hip Joint. Proceedings of the
American Veterinary Medical Asso., p. 191-192,
1952.
5. Durr. J. L., The Use of Kirschner Wires in Maintaining Reduction of Dislocation of the Hip Joint,
Journal of American Veterinary Medical Asso .•
130: p. 78-81, 1957.
6. Hansmeyer. L. L., Fixation After Reduction of
Luxatiol1 of the Coxofemoral Joint in Dogs, The
16
Medical
Asso. 34: p. 459-460, September, 1963.
7. Helper, L. C.. Schiller, A. G., Repair of Coxofemoral Luxation by Extension of the Acetabular
Rim, Journal of the American Veterinary Medical
Asso. 143: p. 709-711, 1963.
8. Knowles. A. T.. Knowles, J. 0., Knowles, R. P .•
An operation to reserve the Continuity of the Hii'
Joint. Journal of the American Veterinary Medical Asso. 123: p. 508-515. 1953.
9. Leonard, E. P., Orthopedic Surgery of the Dog
and Cat, Philadelphia and London. Saunders Co .•
p. 187-207. 1960.
10. MacDonald, D. S., Retention of Coxofemoral Luxations using a purse-string suture, Canadian
Journal of Comparative Medicine'. 28: p. 221-222.
September. 1964.
11. Piermattei, D. L., Technique for Surldcal Management of Coxofemoral Luxatlons, Small Animal Clinicion, 3: p. 373-386, 1963.
12. Vincent, Z. D., The Use of Steinman Stainless
Steel Pin in Recurrent 'Coxofemoral Luxation in
the Dog and Cat, South African Veterinary Medical Journal, 32: p. 42~25, 1961.
Iowa State University Veterinarian