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= 3000 kilo-calories,

or 3,000,000 calories, as the energy value per diem of the food of a man
of about 70 kilos., doing hard muscular work.

This amount is probably a little too high, since the whole of the fat and
carbohydrate of a mixed diet is not assimilated. Rubner estimates the actual
production at 2,843,000 calories. Hultgren and Lantergren, however, found
that Swedish workmen, of an average weight of only 67 kilos., consumed on an
average per diem 159 grms. proteid, 93 grms. fat, and 570 grms. carbohydrate,
which, even allowing for the non-assimilation of a certain proportion of each,
would still give a higher caloric value for the total foodstuffs. Probably,

^ "On the Origin of Muscular Power," London, Edinburgh, and iJuhlin Phil. Mag.,
London, 1866, vol. xxxii. p. 182.

'^ Stohmann, Journ. f. pralct. Chem., Leipzig, 1879, Bd. xix. S. 115 ; Ztschr. f. Biol.,
Miinchen, 1894, Bd. xxxi. S. 364 ;, Arch. f. d. ges. Physiol., Bonn, 1885, Bd.
xxxvi. S. 237 ; Rubner, Ztschr. f. Biol., Miinchen, 1883, Bd. xix. 8. 313; 1885, Bd. xxi.
S. 250 u. 337 ; 1886, Bd. xxii. S. 40 ; 1894, Bd. xxx. S. 73.


therefore, 3000 kilo-calories may be taken as a fair average for the caloric
value of the ingesta of a man weighing about 70 kilos., which would give
about 43 calories for each kilogram body weight. ^

In women the amount is somewhat less than this, both absolutely and also
relatively. In children, though absolutely less, it is relatively greater.

Since the combustion of 1 grm. fat produces 9'3 kilo-calories, and the
combustion of 1 grm. proteid to urea CO., and H^O and of 1 grm. starch
to CO., each produces 4-1 kilo-calories, the combustion of 100 grms. fat
will produce an equal amount of energy with the combustion of 227 grms.,
either of proteid or of starch. This amount, therefore, of proteid or of
starch is said to be of the same " isodynamic value" as 100 grms. fat.
It has been shown by the carefully conducted calorimetric investigations
of Eubner,2 that the isodynamic values are as nearly as possible the
same, whether the combustion occurs in air, or in the tissues of the
animal body.^

Minimal amount of proteid necessary in food. — There has been
much disputation as to the minimal amount of proteid which it is
possible for a man in health and doing work to take in his diet in the
course of twenty-four hours. Eanke gave as a normal diet for an
average man (70 kilos.) not engaged in muscular work, 100 grms. of
proteid, 100 grms. of fat, and 240 grms. of carbohydrate.* Voit
allowed for a man of 70 to 75 kilos., doing ten hours' muscular
work, 118 grms. of proteid, 56 grms. of fat, and 500 grms. of carbo-
hydrate.^ It has, however, been shown that, provided the non-proteids
in the diet are increased — not only in proportion to the caloric value of
proteid withdrawn, but considerably more than in such proportion — a
man can maintain equilibrium and can do work upon considerably less
proteid than that allowed in the diets of Eanke and of Yoit.

Thus Hirschfeld (70 kilos.)'' found that' he could maintain himself for a
considerable time in perfect health with a diminution of proteid down to
75 grms., or even for a time down to 49 grms. per diem, but under these
circumstances it was necessary to increase enormously the amount of non-
proteid and especially of carbohydrate material taken with the diet.

1 Hultgren and Lantergren, working with Tigerstedt, found tlie heat vahie of the food
of six persons living on a freely chosen diet to vary from 33 to 49 calories per kilogramme.
They found that the heat value of the proteid was about 16 to 19 per cent, of the total
heat value of the food, that of the fat being about 21 to 24 per cent., and that of the
carbohydrate about 60 per cent. Eanke's diet {vide infra), with a heat value of only
2,365,000 calories, is for a man performing no muscular work.

2^tec/ir.'/- ^^0^-, Miinchen, 1894, Bd. XXX. S. 73.

" A more complete account of tlie heat vakres of the foodstuffs is given in the article on
"Animal Heat" in p. 833. For the influence of food on the respiratory exchange, see
article "Chemistry of Respiration," p. 717; see also Magnus-Levy, Ao-ch. f. d. gcs.
Physiol, Bonn, 1893, Bd. Iv. S. 1.

•* To this may be added 25 grms. salts and 2535 grms. water (including that contained
in the solid food). These several constituents are contained in a daily ration of 250 grms.
meat, 400 grms. bread, 70 grms. starch or sugar, 100 grms. fat, 10 grms. salt, and 2100
water (J. Eanke, "Die Ernahrung des Menschen," Mimchen, 1876).

° Such a diet contains about 18-3 grms. N", and about 328 grms. C, whereas Ranke's
diet contains about 15-5 grms. IST, and about 220 grms. C. It .should be added that about
13 grms. of the 118 grms. proteid of Voit's diet is not absorbed or assimilated, so that the
available proteid is about 105 grms. This closely corresponds with the results of Bleibtreu
and Bohland (with Pfliiger), who give 1 '5 grms. per kilo, body-weiglit. This would be a
little over 105 grms. for a man weighing 70 kilos. {Arch. f. d. ges. Physiol., Bonn, 1886,
Bd. xxxviii. S. 1). In Hultgren and Lantergren's observations the actual amount of the
ingested proteid which underwent metabolism averaged 101 "3 grms.

^ Arch. f. d. ges. Physiol., Bonn, 1887, Bd. xli.' S. 533 ; and 1889, Bd. xliv. S. 428 ;
also Virchow's Archiv, 1888, Bd. cxiv. S. 301.


Klemperer ^ reduced the amount of proteid in his own diet to as little as
25 grnis. per diem, hut required 262 grms. fat, and 406 grms. carbohydrate
(with a total caloric value of more than 5,000,000 calories) to maintain

I. Munk brought a dog into nitrogenous equilibrium with a diet con-
sisting mainly of proteid. If, now, one -half the proteid of the diet was
removed and replaced by non-proteid, an amount of non-pro teid having a
caloric value of about two-fifths more than that of the proteid removed was
required to maintain equilibrium ; and the more the proteid removed from the
diet, the greater the proportionate amount of non-proteid required. Ultimately,
the amount of proteid was reduced to r5 grms. per kilo, body-weight; under
these circumstances an amount of non-proteid, twelve to fifteen times the
caloric value of the proteid removed, was required to maintain equilibrium.^
After the lapse of some weeks, the animal failed properly to digest the large
amount of non-proteid required, and it became necessary to reduce this and
increase the proteid.

The amount of nitrogen taken in these experiments was distinctly less
than the amount which would be lost in the fasting condition.

Of the two chief kinds of non-proteid food, v. J^oorden and Kayser ^ have
found that carbohydrates are of greater value as proteid-sparers than fats. In
a mixed diet, therefore, containing just enough proteid and non-proteid for
the needs of the economy, fats cannot be substituted for their caloric
equivalent of carbohydrates without loss of proteid occurring. Gelatin is of
still greater value as a proteid-sparing food than are either fats or carbohydrates
(see p. 878), and by its use, although it cannot be built up into tissue, the
amount of tissue proteid lost from the body can be reduced, according to Yoit,
to about the half of that Avhich is normally lost, and which on Voit's estimate
amounts to about 33 grms. daily,"* or 1 per cent, of the actual living substance.^
The importance of gelatin as an article of diet will be specially treated of
later on.*^

In spite of such experiments, it may be doubted whether a diet which
includes considerably less proteid than 100 grms. for the twenty-four
hours could maintain a man of average size and weight for an indefinite
time. It has frequently been asserted that many Asiatics consume a
very much smaller proportion of proteid than is the case with Europeans.
The inhabitants of India, Japan, and China chiefly consume rice as the
normal constitution of their diet, which contains relatively little proteid ;
and this has been advanced as an argument in favour of the view that
the minimal amount of proteid is much less than that ordinarily given
as essential to the maintenance of nutritive equilibrium. It must,
however, be stated that we have no definite statistics to show that, in

1 Arch. f. Physiol., Leipzig, 1889, S. 361. Similar experiments have been made by
Peschel (Diss., Berlin, 1890) and Graham Lnsk, Ztsclir. f. Biol., Mlinchen, 1891, Bd. xxvii.
vS. 459. See also E. Voit, Munehen. med. Wchnschr., 1889, S. 748 ; and C. Voit, ibid.,
1891, S. 195.

'^ Arch. f. Physiol., Leipzig, 1891, S. 338 {Verliandl. d. physiol. Gesellsch.) and
Virchow's Archil; 1893, Bd. cxxxii. S. 91. See also Rosenheim, Arch. f. d. ges. Physiol.,
Bonn, 1893, Bd. liv. S. 61 ; and Ritter, Milnchen. med. Wchnschr., 1893, Nos. 31 and 32.

^Arch.f. Physiol, Leipzig, 1893, S. 371.

•* The half of this amount, since it can be replaced by gelatin, is set down by Voit to
disintegration of "circulating proteid" instead of actual "tissiie proteid."

5 Hermann's "Handbuch," Bd. vi. S. 302, and Ztschr. f. Biol., Mlinchen, 1889, Bd.
vii. S. 284.

•^ Pagliese, Centralhl. f. Physiol.., Leipzig u. Wien, 1897, S. 329, has found that fats,
carbohydrates, and gelatin, not only diminish the amount of the nitrogen excreted, but
also the phosphoric acid, and this even in a greater proportion, and probably by diminish-
ing the waste of the nucleo-proteids of the tissues.



proportion to their body weight, Asiatics doing the same amount of work
as Europeans require a less amount of proteids ; indeed, such evidence as
is forthcoming is rather in favour of the opposite conclusion.^

The following table (from Hultgren and Lantergren) gives the average
amounts of the proteids, fats, and carbohydrates in freely chosen diets of
workmen of different countries, together with the total heat values of such diets :





hard work

Hard work

/Russian workmen (Erismau)
J Munich workmen (Forster)
I^Swedish workmen (H. and L.) .
Swedish workmen (H. and L.) .





With these may be compared the following :-

Soldiers on active service (Voit)







The average proportion of proteid to non-nitrogenous constituents of the
food is given by Hultgren and Lantergren at 1 : 4-27 by weight, and 1 : 4-95
by heat value ; of fat to carbohydrate at 1 : 6-34 by weight, and 1 : 2-80 by
heat value.

The manner in which the proteid and non-proteid constituents of
the diet are most advantageously taken into the body, or, in other words,
the constitution of dietaries, forms a subject belonging more properly to
the domain of personal hygiene. It would, moreover, occupy far too
much space to discuss at all adequately the constitution of diets of
different people and in different countries. It is sufficient to state
that under ordinary circumstances the proteids are taken in such
forms as flesh, egg, and cheese, bread and other cereals, and leguminous
foods, the fat in the form of meat-fat and butter, and the carbo-
hydrate in the form of starch or cane-sugar derived from or contained
in vegetable food. With a purely vegetarian diet the proteid
of the food may be derived largely from the leguminous plants and
to a somewhat less extent from the cereals, and the fat from the seeds
of plants.^ We may now proceed to consider the effects upon nutrition
of some of the more important constituents of the diet.

^ Of. Kumagawa, Firchow's Archiv, 1889, Bd. cxvi. S. 370 ; Kellner and Mori, Ztschr.
/. Biol., Miinchen, 1889, Bd. xxv. S. 102 ; I. Munk, iUd., 1893, Bd. cxxxii. S. 91.

^ For statistics concerning diet see J. Eanke, "Die Ernahrung des Menschen,"
Miinchen, 1876; C. Voit in Hermann's "Handbuch," Bd. vi. ( " Pliysiologie des
allgemeinen Stoffwechsels und der Ernahrung"), Leipzig, 1881; Konig, " Chem. d.
menschl. jSTahrungs-u. Genussmittel," Berlin, 1882, Aufl. 2 ; I. Munk and Uflelmann,
"Ernahrung des Menschen," Wien u. Leipzig, 1887, in which also the literature of the
subject up to that date will be found; Scheube, Mitth. d. deutsch. Gesellsch.f. Nat.-u. Volkerk.
Ostasiens, Yokohama, 1882, No. 24, and^7'c/i./. Hyg., Miinchen u. Leipzig, 1884, Bd. i. S.
352 (diet of Japanese) ; Hultgren and Lantergren, "Untersuch. li. d. Erniihr. Sehwedischer
Arbeitern," Stockholm, 1891 ; Studemund, Arcli. f. d. ges. Physiol., Bonn, 1891, Bd. xlviii.
S.578 ; Ohlmiiller, Ztschr. f. Biol., Miinchen. 1884, Bd. xviii. S. 393; G. Bunge, "DerVege-
tarianisnius," Berlin, 1885; Kumagawa, Virchoiv's Archiv, 1889, Bd. cxvi. 8.370 ; Albertoni
and Novi, Arch.f. d. ges. Physiol., Bonn, 1894, Bd. Ivi. S. 213 (criticised by Hultgren, ibid.,
1895, Bd. Ix. S. 205). Diet statistics will also be found in most text-books of physiology.



Special constituents of the diet. — Proteids. — Proteids are chiefly
taken in the diet in the form of egg-albumin, vitellin, myosin, casein,
the proteids of cereals and of leguminous seeds (mainly globuHns). The
nutritive value of the proteids from any one of these sources is pretty
nearly the same, with the exception that somewhat less of the proteid
of vegetable food is digested and assimilated than that of animal origin,
and the less, the larger the amount of cellulose which is contained in the

Peptones and albumoses have about the same caloric and nutritive
value as the proteids from which they have been formed.^ Certain
proteids are assimilated and have the same nutritive value, if injected
into the blood vessels or under the skin, as when digested and absorbed
from the intestines. This is the case with serum-albumm and serum-
globulin, and also with acid or alkali albumin (even if prepared from
egg-albumin) and phytovitellin.^ Other forms of proteid are not thus
directly assimilable, but on injection appear at once in the urine. Such
are egg-albumin,^ casein,^ peptone, and albumoses. Haemoglobin must
also be reckoned with these, although if injected as blood (with the
blood corpuscles intact), it remains intact. If injected dissolved in
water or in serum, it Ijecomes partly broken up and converted into bile
pigment and partly appears in the urine as haemoglobin.

Most, if not all, proteids contain sulphur, and the nucleo -proteids
contain phosphorus ; an increase of suljohates and sometimes of phos-
phates in the urine may therefore be expected, if theu' metabolism is
increased. The metabolism of ^Droteids wHl be subsequently dealt with.

G-elatin. — Gelatin, although its elementary composition is very
nearly the same as that of proteids, and although it becomes, hke
proteids, converted into peptones by digestion, and after being assimi-
lated is oxidised into urea CO2 and H2O, is different from proteids in
its chemical constitution (see " Chemical Constituents of Body and
Food, pp. 31 and 70), and cannot wholly replace proteid as an article
of diet. This arises from the fact that the bioplasm of the tissues
is unable to be produced from it. In spite, therefore, of its con-
taining nitrogen and all the elements of the proteid molecule, it is a
non-proteid food, and takes its place as such along with the fats and
carbohydrates. Like them also it acts as a proteid-sparer, so that a
certain amount of proteid can be removed from the diet and replaced
by gelatin ; about twice as much of this must, however, be added, as
proteid is removed.^ As a proteid-sparer, gelatin acts more efficiently
than carbohydrates, and still more than fats. This is shown by an
experiment by Voit upon a dog weighing 32 kilos., which had been
maintained very nearly on nitrogenous equilibrium by a daily allowance

1 Politzer, Arch. f. d. ges. Physiol., Bonn, 1885, Bd. xxxvii. S. 301.

- Plosz and Gyergai, Arch. f. d. ges. Physiol., Bonn, Bd. ix. S. 325, and Bd. x. S. 536 ;
Maly, ibid., Bd. ix. S. 605; Adamkiewicz, Virchows Archiv, Bd. Ixxv. S. 144; Stokvi.s,
Centralhl. f. d. med. JVissensch. , Berlin, 1864, S. 596; Lehmann, Virrhoivs Archiv, 1864,
Bd. XXX. S. 593 ; Ponfick, Virchovfs Archiv, 1875, Bd. Ixii. S. 273 ; Forster, Ztschr.
f. Biol., Miinchen, 1875, Bd. xi. S. 517 ; Tizzoni, Arch. ital. dc hiol., Turin, 1884, Bd.
vi. S. 395; Neumeister, Sitzungsh. d. phys.-mcd. Gesellsch. zu Wurziurg, 1889, S. 64/
Ztschr. f. Biol, Miinchen, 1891, Bd. xxvii. S. 309.

^ Bernard, " Lecons sur les propr. physiol. etc.," Paris, 1859, tome ii. p. 467.

■* Runeberg, JDeutschesArch.f. klin. Med., Leipzig, 1879, Bd. xxiii. S. 68.

•' According to Voit, one-tii'th of the ordinary ainount of proteid may be so replaced. I.
Munk, however, in the dog got at least two-thirds of the proteid of the food replaced
by gelatin \\-ith maintenance of equilibrium [Arch. f. d. ges. Physiol., Bonn, 1894, Bd. Iviii.
S. 309, and Bd. Ixi. S. 607).



of 500 grms. of meat. On removing 100 grms. of this from the diet, and
replacing it Idj 200 grms. of gelatin, there was a gain of nitrogen to the
body representing the putting on of 44 grms. of flesh, whereas when the
100 grms. of meat was replaced by 200 grms. of fat, or by 250 grms. of
starch, there was a loss of nitrogen representing a loss of flesh to the
amount respectively of 50 and 39 grms.

The following experiments of Voit on a dog are also instructive.
The numbers represent grammes : —


Lean Meat.


Flesh lost or gained.





+ 54



+ 30

2. \




+ 376





3. J








+ 25

^- 1




That it cannot wholly replace proteid is shown by the fact that
even when very large quantities are given either alone or in combination
with fat and carbohydrate, an excess of nitrogen appears in the excreta
— in other words, there is still a loss of flesh from the body.^ To a
certain extent gelatin will act as a fat-sparer, i.e., when given along
with proteid, it may prevent the oxidation of body fat, but its activity in
this respect is far below that of either fats or carbohydrates.^ Even
the collagenous tissues can apparently not be formed from gelatin
ingested, since this wholly appears (as urea, etc.) in the excreta ; these
tissues must therefore be formed, like all others, from proteid food.^
Grelatin is also not assimilated if injected into the blood or under the
skin ; it appears at once in the urine.^

Nucleins and nucleo-proteids, as well as lecithins, are found in all
forms of mixed diet ; and although nuclein is not digested by the gastric
juice, nor, according to Bokay,^ by artificial pancreatic juice, there are
reasons for believing that a part at least of the nuclein of the food is
absorbed and converted in the body into other substances. It is found,
for example, that the ingestion of foodstuffs containing much nuclein
causes a marked increase of uric acid in the urine,^ and, as we shall
show later on, there is strong reason to believe that the iron necessary
for the formation of hsemoglobin is derived from some forms of nuclein.

^ For the evidence of this, see C. Voit, oj). cit., S. 122.

' C. Voit, op. cit., S. ]26.

3 An interesting historical account of the question of gelatin as an article of diet is
given by Voit {op. cit., S. 395).

* 01. Bei-nard and Barreswil, Jowm. dc pharm. et chim., Paris, 1844, Ser. 3, tome v.
p. 425.

^ Ztschr. f. physiol. C'hem., Strassburg, 1877, Bd. i. S. 157.

'' Horbaczewski, Sitziongsb. d. k. AJcad. d. ?Fissensch.,WieD, 1891, Bd. c. Abtli. 3, S. 78,


The phosphorus of any nuclein which is absorbed is probably converted
into phosphoric acid, and excreted as phosphates by the urine. There
is no evidence tliat the nuclein which is absorbed is taken up by the
tissues, and by them again converted into tissue nucleins ; it is more
probable that these arise by independent synthesis from proteid and
phosphates. That this may occur was shown by Miescher,^ who found
in the case of the salmon, which travels from the sea to the upper
Ehine, there to deposit its spawn, and which during the whole period of
its journey and sojourn in the river, lasting some weeks or even months,
takes no food whatever (the alimentary canal being always found empty),
that the ovaries increase in size at the expense of the muscular tissue.
Now the ovaries, bemg mainly composed of ova, contain large quantities
of nuclein and lecithin, whereas the muscles contain mainly ordinary
proteids and very little of these substances ; the latter must therefore
be formed by synthesis, the materials for such synthesis being derived
from the proteids, the fats, and the phosphates of the muscles.

Amido- acids. — Experiments to determine the nutrition, and
especially the proteid-sparing value of amido -acids, have chiefly been
made with asparagin, which occurs in some quantity in certain vegetables.
The general result of these inquiries is to show that in herbivora (rabbit,
goose, sheep), the amido-acids can act ?s proteid-sparers, whereas in
carnivora (dog) and omnivora (rat) they have not proteid-sparing
effects when added to the diet.^

Creatine has been found to have no nutritive value. If given with
the food, it appears wholly in the urine as creatinine.^

Carbohydrates. — Apart from the small amount of glycogen or sugar
which may be contained in flesh foods, and from the lactose of milk, the
carbohydrates of the food are wholly derived from the vegetable king-
dom. The chief carbohydrate constituents of an ordinary diet are starch
and cane-sugar, with a certain amount of grape-sugar when there is
much consumption of certain fruits. Neither starch (in solution) nor
cane-sugar (Bernard) is directly assimilable when injected into the blood
vessels, and the same is true for maltose and lactose. "^ These sub-
stances all appear under such circumstances at once in the urine.

On the other hand, dextrose can be directly assimilated, even in large
amounts. It is necessary that the injection should be conducted slowly,
so that the liver should have time to convert it into glycogen before the
proportion of dextrose in the blood much exceeds about 0'2 per cent.
Injected too rapidly, or in too large doses (more than 1 grm. per kilo,
body weight), glycosuria results ; ^ and if its elimination by the kidneys

1 Arch.f.Aiiat. u. Entivcklngsgecch. , Leipzig, 1881, S. 193 ; and "Statistische u. biol. Beitr.
z. Kenntniss vom Leben des Rheinlachses," 1880 (quoted from Bunge's " Handbuch ").

2 Weiske, Ztschr. f. Biol., Miinchen, 1879, Bd. xv. S. 261 ; 1881, Bd. xvii, S. 415 ;
1884, Bd. XX. S. 277 ; 1894, Bd. xxx. S. 2.54 ; Zuntz and Balilmann, Arch. f.
Physiol., Leipzig, 1882, S. 424 {Verhandl. d. iihys. Gesellsch.) ; Potthast, Arch. f. d. ges.
Physiol., Bonn, 1883, Bd. xxxii. S. 280 ; L Mnnk,'Vircho2v's Archiv, 1883, Bd. xciv. S. 436 ;
and 1884, Bd, xcviii. S. 364 ; Mauthner, Ztschr. f. Biol., Miinclien, 1892, Bd. xxviii.
S. 507 ; E. A^oit, SitvMngsh. d. Jc.-bayer. Akad. d. IVissensch. zu Miinchen, 1883, S. 401 ;
Ztschr. f. Biol., Miinclien, 1892, Bd. xxvii. S. 492; 1893, Bd. xxix. S. 125; Gabriel, ibid.,
S. 115.

3 Meissner, Ztschr. f. rat. Med., 1868, Bd. xxxi. S. 283.

* According to Dastre {Arch, dephysiol. norm, etpath., Paris, 1889, p. 718), galactose is
directly assimilable.

° Biedl and Kraus ( Wien. Iclin. Wchnschr., 1896, S. 55) state, however, that they were
able to inject as much as 200 to 300 grms. of grape-sugar, in 10 per cent, solution, into the
vein of a man, without jjroducing either polyuria nor any but a slight temporary glycosuria.


be prevented, as by tying the ureters, the excess of sugar under-
goes changes which result in the formation of lactic acid, acetone,
diacetic acid, and other substances, the production of which is
accompanied by convulsions, and eventually coma, as in severe natural

Very large amounts of starch can be taken into the alimentary canal,
and corresponding amounts of dextrose absorbed into the blood, without
producing glycosuria in a normal animal. But if the assimilation
powers have been reduced by starvation, glycosuria is found to occur on
the ingestion of a large amount of starch.^ On the other hand, if cane-
sugar, maltose or lactose, and even Isevulose, are taken by the mouth in
large quantities, even without a previous starvation period, part of the

Online LibraryE. A. (Edward Albert) Sharpey-SchäferText-book of physiology; (Volume v.1) → online text (page 122 of 147)