E. A. (Edward Albert) Sharpey-Schäfer.

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pressure in the dog ; one vagus only cut ...

89. The same with both vagi cut . . .

90. Tracing showing effect of suprarenal extract upon heart, limbs, spleen

and blood-pressure, after section of cord and vagi

91. Tracing showing effect of suprarenal extract upon blood-pressure and

limb-volume .......

92. A^ Ergograph tracing of a person sufferiug from Addison's disease. B.

Tracing made from the same person after six weeks' treatment with
suprarenal extract (Langlois) .....









By W. D. Hallibukton.

CoNTE^^TS : — The Carbolivdrates, p. 2 — Tlie Fats, p. 17 — Lecithin, p. 21— Choles-
teriu, p. 22 — Tlie Proteids, p. 24 — Decomposition Products of Proteids, p. 28 —
Synthesis of Proteids, p. 35 — Theories of Proteid Constitution, p. 38 — General
Properties and Reactions of Proteids, p. 39 — Classification of Proteids, p. 49 —
Vegetable Proteids, p. 51 — Poisonous Proteids, p. 55— Compound Proteids, p. 61
— The Albuminoids, p. 69 — Inorganic Compounds, p. 76.

The chemical constituents of the body are very numerous, and the
majority of them are compounds of comphcated structure. In the
following article I propose to treat of these compounds, first in classes,
and then indi\ddually, and in a subsequent chapter to discuss the various
tissues and organs in their chemico-physiological aspects.

In order to classify the chemical constituents of the body, one might
proceed upon a purely chemical basis, beginning with the simplest and ending
with the most complex compounds ; or a purely physiological basis might be
adopted, in Avhich the compounds would be described in the order of their im-
portance in the vital processes of the organism. But a compromise between these
two exclusive methods is found to be that which is of most practical usefulness.

We may, in the first place, divide the compounds found in the body
into those of inorganic, or mineral natm-e ; and those which are termed
organic, or carbon compounds.

The morganic compounds present are water ; various acids, such as
the hydrochloric acid of the gastric juice ; and nimierous salts, such as
calcium phosphate in bone, and sodium chloride in blood, urine, etc.

The organic compounds are more numerous, and these we may
conveniently group as follows : —

[Proteids, e.g. albumin, myosin.
ISTiTROGENGUS . - Albuminoids, e.g. gelatin, keratin.

[Simpler nitrogenous substances, e.g. lecithin, creatine.

( Fats.
NoN-NiTROGENOUS -j Carbohydrates, e.g. sugar, starch.

[simpler organic substances, e.g. alcohols, lactic acid.

VOL. I. 1


The most useful classification of the more complex organic com-
pounds is the time-honoured one, into proteids, carhohydrates, and
fats. Taking this as om- starting-point, we shall find that the other
substances present maj be described either in subsidiary classes to
these, or as decomposition products of the more complex substances.

The elements found in these compounds are carbon, hydrogen,
nitrogen, oxygen, sulphur, phosphorus, chlorine, iodine, fluorine, silicon,
sodium, potassium, calcium, magnesiiun, hthium, iron, and occasionally
manganese, copper, and lead.

It will be on the whole most convenient to study the organic
compounds first, in the following order : —

1. Carbohydrates ;

2. Fats, with which we shall study the lecithins and cholesteriiis ;

3. Proteids and albuminoids.

In following out this plan we shall discuss some of the chemical
constituents of the food as well as those of the body.

The Carbohydeates.

The carbohydrates are found chiefly in vegetable tissues, and many
of them form important foods. Some, however, are found in or formed
by the animal organism, such as glycogen or animal starch, dextrose, and
lactose or milk-sugar. The carbohydrates may be conveniently but
loosely defined as compounds of carbon, hydrogen, and oxygen, the
two last-named elements being in the proportion in which they
occur in water. But this definition, if pushed, would include several
substances like inosite, acetic acid, and lactic acid, which are not

The work of Fischer,^ Tollens,^ and many other chemists has,
moreover, shown that carbohydrates are not, as then- name would
imply, simply compounds of carbon with water, but then- constitutional
formula has been in many cases thoroughly worked out, and their
composition shown to be much more complex. This work has culminated
in the synthetical production of many of the sugars.

From the chemical standpoint, the sugars (which are the simplest
of the carljohydrates) maj^ be divided into two classes —

1. Those which, when digested with dilute acids, do not yield any
other sugar or sugars ; this class includes the glucoses ; and

2. Those which, when so treated, do yield some other sugar or sugars ;
this class includes the members of the cane-sugar group.

Further, the sugars are designated according to the number of
carbon atoms they contain ; thus we have trioses {e.g. glycerose), tetroses
{c-.g. erythrose), pentoses {e.g. arabinose, xylose, rhamnose), hexoses {e.g.
glucose, mannose), heptoses, octoses, and nonoses, according as they
contain, three, fom-, five, six, seven, eight, and nine atoms of carbon
respectively in their molecules.

The great majority of these sugars possess, however, l)ut little

^ See especially E. Fisclier, Bcr. d. deutsch. chem. Gesellsch., Berlin, Bd. xxiii. S. 2114.
' Tollens. " Knrzcs Handbucli dcv Kolilenliydratc," Brcslan.


physiological interest, and their chemical relationships and reactions
will be found described in works on chemistry.^

Those which are of physiological importance are the hexoses and
their derivatives. Nearly all the carbohydrates with which we have
to deal in the animal body contain either six carbon atoms, or some
multiple of six. The same is true of those which are used as food. The
remainder are either synthetical products of the chemical laboratory, or
more or less rare products of the vegetable world.

But to this rule there is one exception ; the pentoses do possess some
physiological importance. When Hamniarsten ^ was investigating the nucleo-
proteid material he separated from the pancreas, he found that by boiling it
with dilute mineral acid he obtained a reducing substance. This formation
of a reducing sugar-like substance from nuclein is not unique, as Kossel ^ and
his pupils have obtained a similar product from yeast-nuclein. The sugar,
however, does not ferment with yeast, but, like the pentoses, gives a red
coloration with phloroglucinol and hydrochloric acid, and by distillation with
hydrochloric acid yields furfuraldehyde. An osazone is obtainable from it
in the form of fine rosettes of crystals, melting at 158° to 160° C, and these
appear to be identical with those prepared from pentoses by E. Salkowski
and M. Jastrowitz.'*

The physiological action of pentoses was investigated by W. Ebstein.^
When xylose or arabinose, dissolved in water or coffee, are taken with the
food, they rapidly appear in the urine ; they are not assimilated. The use of
fruits, such as pears, that contain jmntosanes, the mother substances of pentoses,
may lead to the appearance of the latter substances in the urine. It is
of course important not to confound such a temporary condition with diabetes.

Max Cremer ^ has investigated the physiological action of some of the rare
sugars, especially their influence on the formation of glycogen. He found that
in rabbits mannose increases the hepatic glycogen, and that, though the
pentoses readily pass into the urine, a small quantity is assimilated as glycogen.
Lindeman and May '^ have confirmed Cremer's results.

Salkowski ^ has investigated a large number of diabetic urines, but was
unable to find pentose in any of them. ^Nevertheless, he found pentose in
various other morbid conditions in the urine, in which their presence could
not be attributed to diet. He suggests that in these cases they originate in
the body from such nucleo-proteids as Hammarsten found in the pancreas, the
processes of oxidation being lessened so that they were not broken up into
simpler materials.

'We can now proceed to the study of the carbohydrates concerning
which we have more accurate physiological knowledge : and these may
be classified into the following three groups : —

1 See article '•'Sugars," Watts's "Dictionary of Chemistry, " Loudon, 1S94, vol. iv.

- Ztschr. f. 'physiol. Chemi., Strassbiirg, Bd. xix. S. 19.

^ Kossel and Neumann, Be?: d. deutsch. cheiu. Gesellscli., Berlin, Bd. xxvii. S. 2215.

^ Centralbl. f. d. vied. Wissensch., Berlin, 1892. Nos. 19 and 32. Blumenthal {Berl. Jclin.
iVchnschr., 1897, Bd. xxxiv. S. 245) has obtained pentoses from numerous other nucleo-

6 Firchow's Archiv, Bde. cxxix. S. 401 ; cxxxii. S. 368 ; cxxxiv. S. 361.

'^ Ztschr. f. Biol., Mtlnchen, Bd. xxix. S. 484.

' Chem. Centr.-BL, Leipzig, 1896, Bd. i. S. 932.

^ Berl. klin. Wchnsehr., Bd. xxxii. S. 364. See also Ktilz and Vogel {Ztschr. f. Biol.,
Mlinchen, 1895, Bd. xxxii. S. 185). These observers found pentoses in only four out of
sixty-four cases of human diabetes. But they are generally found in the severe forms of
diabetes produced in dogs by the extirpation of the pancreas or by administration of


1. Monosaccliarides (C^H^^oO^). — The most important members of this
group are :



2. Disaccharides (CjoH.^oO;^^. — The most important' members of this
group are :

Cane Sugar.


3. Polysaccliarides (C^jH^qO.-,),,. — The most important members of this
group are :

I Cellulose.







The monosaccharides. — When an alcohol is oxidised, the first
stage in oxidation is the formation of an aldehyde, or a ketone ; if
oxidation of the aldehyde is continued, an acid is formed.

When more complicated alcohols are oxidised, similar products result.
The monosaccharides are the first oxidation products of the hexatomic
alcohols (CH,.0H—(CH.0HX—CH20H).

Of the hexatomic alcohols, three are known, namely sorbite, mannite,
and dulcite.

Dextrose is the aldehj^de of sorbite.^
Mannose ,, ,, mannite.

Galactose ,, ,, dulcite.

Levulose ,, ketone of mannite.

Sugars of the monosaccharide group may thus be either aldehydes,
when they are called aldoses ; or ketones, when they are called Icetoses.

Dextrose, mannose, and galactose are aldoses, and have the structure
represented by the following formula : —


They differ from one another in theh stereochemical formulae.
Levulose is a ketose, and has the structure represented by —

CH2.OH— (CH.0H.)3— CO— CH.2— OH

The difference between the aldoses and ketoses is shown by oxidation,
levulose, like all ketoses, yielding acids which are poorer in carbon.

If chlorine or bromine water is used as the oxidising agent, -the
aldoses (dextrose, mannose, and galactose) give isomeric monobasic acids
of the formula — •

CH2.OH— (CH.OH) — COOH ;

and then, by further oxidation by means of nitric acid, yield dibasic
acids of the formula —


Both sets of acids are stereo-isomerides.

Monobasic acid. Dibasic acid.

From Dextrose . . . Gluconic acid Saccharic acid.

„ Mannose . . Mannonic acid Manosaccharic acid.

„ Galactose . . Galactonic acid Mucic acid.

\Meunier, CompL rend. Acad. d. sc. Paris, tome cxi. p. 49; Vincent and Dclachanal,
ihi'L, p. 51.


GlycAtronic acid. — If saccharic acid is heated five or six hours in the
water bath, it is changed into saccharo-lactonic acid, CgHgO-. If this is
reduced by means of sodium amalgam, one obtains glyciironic acAcl ; ^ this
substance is of considerable interest because it is sometimes found in the
body, and when it passes into the urine is apt to be mistaken for sugar,
many of the tests for which it gives.

Its composition is —

COOH— (CH.OH),— CHO = Q,^^,0,

It is soluble in water and alcohol, is dextro-rotatory, reduces alkaline
solutions of metallic salts, and yields saccharic acid on oxidation with
bromine. It does not undergo the alcoholic fermentation. Though
related in its composition so nearly to the carbohydrates, it yields with
urea decomposition products which are aromatic, such as orthonitro-
benzyl alcohol (Jaffe).- It occurs in the mine in the form of the
potassium salt (CgHgO-K) after the administration of chloral and
butylchloral,^ nitrobenzol,^ orthonitrotoluol,^ camphor,^ etc. It also
occurs in the m-ine after chloroform narcosis, and in the paralytic
secretion that takes place on section of the renal nerves.'' Occasion-
ally it is found without any apparent cause, as a result of disordered

Levulose on oxidation always yields acids containing less carbon
atoms than itself, namely, trioxybutyric (CH„OH(GH.OII).,COOH),
formic (H.COOH), and glycolHc (CH^.OH.COOH)" acids. But ^different
acids are yielded by different methods of oxidation; thus chlorine or
bromine and silver oxide oxidise levulose to glycollic acid ; * nitric acid
yields oxahc, tartaric, glycollic, acetic, and other acids.''

Synthesis of sugars. — The first step towards the synthesis of the sugars
was made by Butlerow.^'^ He obtained a sugar-like substance by adding lime
water to a solution of dioxymethyleiie ; this he termed niethylenitan,
and gave its formula as C-Hj^Og. Loew ^^ next obtained a condensation
product of formaldehyde (CHoO) by means of Kme Avater; to this substance
he attributed the formula {Gf^-^^O^), and called iiforniose.

x^either methylenitan nor formose ferment with yeast. Fischer '^-
investigated these substances, and found that they were mixtures of two
sugars, one of which is formose (C(3HjoO,3), and another a-acrose ^^ (C^HjoOg),
both of which yield crystalline osazones.

From the osazone which is yielded by a-acrose the sugar can be again

1 H. IhitrhlAer, Ztsclir.f. lohysiol. C%e7?i. , Strasshurg, 1887, Bd. xi. S. 388; 1891, Bd. xv.
S. 71 ; Ber. d. deutsch. chem. Gesellsch., Berlin, 1886, Bd. xix. S. 3148; E. Fischer and
0. Piloty, ibid., 1891, Bd. xxiv. S. 521.

" Ztsclir. f. 2}hysioL Chem., Strassburg, Bd. ii. S. 47.

^ Musculus and v. Mering, Arch. f. d. ges. Physiol., Bonn, Bd. xx. S. 64.

■^ V. Mering, Ccntralbl. f. d. med. TFissensch. , Berlin, 1875, No. 55.

^ Jafte, loc. cit.

*> Sclimiedeberg and Meyer, Ztschr. f. x>hy>iiol. Chem., Strassburg, Bd. iii. S. 422.

"^ Ashdown, Brit. Med. Journ., London, 1890, vol. i. p. 171.

^ Hlasiwetz and Haberniann, Ann. d. Chem., Leipzig, Bd. civ. ; Kiliani, ihid., Bd.
civ. S. 175.

'^ Kiliani, ihid., S. 162 ; Hornemann. Journ. f. praTct. Chem., Leipzig, Bd. Ixxxix. S. 283.
^° Ann. d. Chem., Leipzig, Bd. cxx. S. 295 ; Conyjt. rend. Acad. d. sc, Paris, tome Iii.
p. 145.

^' Journ. f. jjrakt. Chem., Leipzig, Bd. xxxiii. S. 321.

^^ Ber. d. deutsch. chem. Gesellsch.. Berlin, Bd. xix. S. 2133.

^^ Acrose is a sngar obtained by Fischer, ibid., Bd. xx. S. 1093 and 2566, by acting on
acrolein bromide with bases (2C3H^OBr2-l-(2Ba(OH)„ = C6HioOo +2BaBro ; two isomeric
sugars, a- and /3-acrose are thus produced.


obtained by reduction tbrougli tbe intermediate osone (see p. 9). The sugar
obtained is identical with levulose or fructose, except that it is optically inactive.
If this inactive levnlose (i-levnlose) is submitted to the action of yeast, the
levorotatory constituent (c?-levulose) ferments, and the residue is dextro-
rotatory. This is Z-levulose,i but it is not the natural sugar. The natural
sugar -was formed in the follomng way : — a-acrose was reduced to the corre-
sponding alcohol, a-acrite, which is identical with ^-mannite; from this the
sugar 2-mannose Avas obtained, which Avas fermented, and Z-mannose alone
remained. By further oxidation t'-mannose yields t'-mannonic acid. By
fractional crystallisation of the morphine or strychnine salt of this acid, it can
be separated into its two active (cl and Z) constituents, and from these the
corresponding sugars (mannoses) are obtained by reduction, and these by
means of the ozones into the corresponding levuloses, the cZ-leyuIose being
the levorotatory natural sugar.

In order to get dextrose, the d- and Z-mannonic acids are heated with
quinoline ; this partly decomposes these acids, yielding d- and /-gluconic acids,
and by reduction of these acids the sugars rZ-glucose (or dextrose) and Z-glucose
are obtained.

Of the numeroiLS sugars in the monosaccharide group, dextrose,
levulose, and galactose possess special physiological interest.

Dextrose is found widely distriliuted in uatiu'e in grapes, and many
other fruits ; also in seeds and roots, and in honey. It is generally
mixed with levidose. In the animal body it is the final result of the
digestion of starch, and occurs in small quantities in the blood and
lymph ; traces only occur in normal lu'ine. The quantity both in the
blood and urine is increased in dialjetes. It crystallises either in fine
needles, free from water of crystallisation, or with 1 molecide of water of
crystallisation in small plates; these melt at 100"" and lose their water
at 110° C. The water-free crystals melt at 146" and at 170° C. lose
water, the residue being glucosane (CgHioOj). By higher temperatm-es
it is converted into caramel.

Dextrose is readily soluljle in water ; the sohition is not so sweet as
one of cane-sugar; it is dextrorotatory. The specific rotation ^ varies
with tempera tm^e and concentration, but at 20° C. averages +52° '6.
A freshly-made solution may have nearly double this rotatory power,
but on standing for some time, or on heating the solution, the rotation
becomes normal. Dextrose is slightly soluljle in cold, very soluljle in
hot alcohol. It is insoluble in ether.

Levulose is found with dextrose in the vegetable kingdom, and in
honey. It is formed 1jy the hydrolytic splitting of cane-sugar and otlier
carbohydrates, but is oljtainable with special ease from inidin. It is
occasionally found in diabetic urine.^ In many cases of diabetes it may
be used with impunity in the food.

^ The I, i, and cl are prefixes pnniarily attached to isomeric sugars, to indicate their action
en polarised light, whicli is due to the presence and piosition of an asjaiimetiic carbon atom.
The terms were introduced hy Fischer to denote this character, hut they have been extended
to comprise derivatives of the original sugar, is-hicli derivatives may liave the opposite
rotatory power, as is seen in tlie above example, where a d sugar is levo- and an I sugar is

^ The specific rotation (a)D of any substance is the amount of rotation in degrees of a
circle of the plane of polarised light, produced by 1 gi-m. of tlie substance dissolved in
1 c.c. of liquid, examined in a tube 1 decimetre long. It is measured for yellow (sodium)

' Leo {Virchow's Archiv, 1887, Bd. cvii. S. 108) has found as an occasional constituent
of diabetic urine, a levorotatory sugar which is not levulose. Its reducing power is small,


Its crystals, which are difficult to obtain, are partly water-free
(CyHi20,j) and partly contain water of crystallisation (2CeHi206.H20).
Levulose is different in chemical constitution from the other sugars we
have studied in this group. It, however, gives the same general tests ;
but its specific rotatory power has not been satisfactorily determined.

Galactose, is obtained by the hydrolytic decomposition of lactose or
milk-sugar, and from many other carbohydrates, especially gmns and
mucilages. It is obtained by the decomposition of a glucoside occmring
in the brain called cerel^rin.^ It crystallises in needles or plates, which
melt at 168° C. It is somewhat more difficult of solution in water than
dextrose, and more strongly dextrorotatory.

Mannose or seminose is another monosaccharide which is of scientific
interest, as it is the aldehyde of the alcohol (mannite) of which levulose is the
corresponding ketone.

It does not occur free in nature. It is obtained from mannite by
oxidation,- and also by the action of dilute sulphuric acid on the so-called
reserve cellulose.^

Reactions of the monosaccharides. — (a) Fermentation. — They are
dkectly fermentable by yeast into alcohol and carbonic acid (CgHiaOg
= 202115.011+2002) ; and by the Bacterium Iccetis into lactic acid (OgHi206
= 2OII3 — OH.OH. — OOOH). But this property of fermentation is only
possessed by those which occur in nature.

(b) Reducing power. — Being aldehydes or ketones, they are easily
oxidrsable, and reduce metallic oxides in alkaline media.

They cause a deposition of metallic silver in an ammouiacal silver solution
containing some caiTstic soda ; and of metallic bismuth from basic bismuth
nitrate suspended in soda (Bottcher's test) ; and of the red cuprous oxide (CuoO),
or of the yellow cuprous hydrate Cu(0H2), from an alkaline solution of cupric
oxide, as in Trommer's and Fehling's tests.*

(c) When heated in the dry state, before they char, they yield a
brownish product called caramel. A similar substance is formed by
boiling with- alkalies (Moore's test).^ In the brown substance formed,
among other bodies is levulinic acid, OH3 — CO — OH2 — OII2 — OOOH.

its rotatory power weak («d - 26) ; it forms au osazoue. Neubauer and Vogel
(" Anleitang znr qualitativen und quantitativen Analyse desHariis," 1890) suggest the name
"laiose " for it.

^ Thierfelder, Ztschr. f. physiol. Chem., Strassburg, Bd. xiv. S. 209; Bro-mi and
Morris, Proc. Ohem. Soc, London, 1889, p. 167.

- Fischer and Hirschberger, Ber. d. deutsch. chem. Gevellsch., Berlin, Bde. xxi. S. 1805 ;
xxii. S. 11.55 and 3218. ' ^ y^qI^s, ibid., Bd. xxii. S. 909 and 3218.

^ In Allihn's method {Journ. f. prakt. Chem., Leipzig, Bd. xxii. S. 55) of estimating
the reducing power of a sugar, tlie cuprous oxide obtained by Fehling's method is collected
and weiglied as metallic copper. Pfiiiger {Arch./, d. ges. Physiol., Bonn, 1877, Bd. IxA'i. )
reconmiends that the cuprous oxide should be dried at 120^ and weighed. O'Sullivan and
Stern {Journ. Chem. Soc, London, 1896, p. 1691), who have recently prepared dextrose
from several sources, have found that 1 gr. of CuO is reduced by 0*4535 gr. of dextrose
(1 gr. CuoO = 0"5045 gr. dextrose). On the relation between reducing power and specific
rotation see a series of papers by H. T. Brown, G. H. Harris, and J. H. Millar (Proc.
Chem. Soc, London, 1896, pp. 241-244). If the reducing power of dextrose is taken as
100, that of levulose is 92 to 94 (ibid., 1897, p. 4).

^ F. Freimm (Arch. f. d. ges. Physiol., Bonn, 1896, Bd. Ixiv. S. 575) has found that
Moore's test is accompanied by the formation of products of oxidation, namely aldehyde
and formic acid.


id) Fhcnyniydrazine test. — This is carried out in the following
way : —

To 5 c.c. of a solution of sugar (■which should not he stronger than 0'5 per
cent.) 1 decigramme of phenylhydrazine hydrochloride and 2 decigrammes of
sodium acetate are added, and the mixture heated on the "water hath for
half an hour. On cooling, if not hefore, a crystalline or amorphous pre-
cij^itate separates out. If amorphous it may he dissolved in hot alcohol,
the mixture diluted with -water, and hoiled to expel the alcohol, whereupon

Fig. 1— Cn'stals of phenylglucosazone.

the compound or osazone separates out in yellow crystals. It is important
that there should he an excess of phenylhydrazine.

Dextrose gives a precipitate of phenylglucosazone {Q^^\.J.^^O^),
which crystallises in yellow needles (melting-point 205° C). Levulose
and mannose }deld osazones identical with this.

Galactose yields a very similar osazone (phenylgalactosazone). It
differs fiom phenylglucosazone hy melting at 190—193'' C, and in heing
optically inactive when dissolved in glacial acetic acid.

The chemistr}' of the reaction is represented in the following
equations : —


1. CH/JH[CH(0H)]3CH(0H)C0H + H2N.NH(C,H5)

( (piienylhydrazine)


II +H/3

^N-— NH(C6H,)

(hyclrazone) (water)


II +C0H5.NH— NH,


(hydrazone) (phenylhydrazine)

= ' II II +H, +H„0

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