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condition of myosin fibrin directly ; whilst in the passage of myosinogen
into the state of myogen fibrin, there is an intermediate soluble stage
coagulable by heat, at the remarkably low temperature of 40'"' C.^

Paramyosinogen is described as a typical globulin, and is regarded as
identical with Kiihne's myosin which he obtained by dropping muscle plasma
into water. Myosinogen is described as differing from a globulin in some
particulars, and is spoken of as a proteid sui generis. Myoglobulin is not
regarded as a separate proteid, but as part of the myosinogen which has
escaped coagulation. The phenomenon regarded by Chittenden and myself as
re-coagulation of myosin is considered to be a simple re-precipitation of globulin.
Whitfield's work on the absence of peptones and proteoses is confirmed.

The muscle plasma from fishes' and crabs' muscle contains another proteid,
called myo-proteid. It gives the usual proteid reactions, and is readily digested
by gastric juice ; though precipitated by a removal of the salts by dialysis, it
is not coagulable by heat. It is precipitable by acetic acid, but is neither a
mucin nor a nucleo-proteid.

In his second paper, v. Furth treats of (1) the properties (solubilities,

1 Ztschr.f. i^hysiol. Chem., Strassburg, 1896, Bd. xxii. S. 245.

2 lUd., 1886, Bd. x. S. 248.

^ Arch. f. exper. Path. it. Pharmakol., Leipzig, 1895, Bd. xxxvi. S. 231; also ihid.,
1896, Bd. xxxvii. S. 389.

* J. H. Milroy {Arch. f. Hycj., Miiiichen u. Leipzig,1896, Bd. xxv. S. 154) has also made
quantitative estimations of the various muscle proteids coagulable at different temperatures.

^' If the reader refers to my memoir on "Muscle Plasma," he will find, on p. 186, that I
accidentally noted this fact, thougli I failed to appreciate its meaning. In frogs' muscle
plasma there is a considerable amount of this soluble myogen fibrin in a "preformed"
condition (v. Flirtli). The separation of the muscle proteids liy fractional heat coagulation
fits in exactly with Brodie and Richardson's work on heat rigor ; as the temperature of a
muscle is raised, successive shortenings occur at the coagulation temperature of each
proteid {Proc. Roy. Soc. London, 1897, vol. Ixi. p. 77).



SKELETAL MUSCLE.



99



effect of numerous reagents, etc.) of myosinogen and paramyosinogen; (2) the
influence of blood serum in hindering the coagulation of the muscle plasma ;
and (3) the action of various chemical substances on living muscle.

Involuntary muscle,. — Our chemical knowledge of involuntary muscle
is of a fragmentary nature. Like voluntary muscle, the heart becomes
rapidly rigid after death, and simultaneously acid,^ from the formation of
sarcolactic acid. Both paramyosinogen and myosinogen are present in
the muscle cells of the heart, and myosin is the result of coagulation.
In the stomach and uterus, rigor has been observed, but in other forms
of plain muscle it is difficult to recognise. A proteid coagulating at
56° C, has been obtained from all kinds of unstriped muscle. In a
muscular tumour of the uterus, Kossel ^ found the one coagulating at
45° C. (paramyosinogen) to be absent.

The reaction of unstriped muscle is normally alkaline.^ Lehmann ^
found small quantities of lactic acid in the muscular substance of the
stomach after death. There is, however, no marked change in the
reaction after death, as in striated muscle. Du Bois-Eeymond ^ observed
in the stomach and intestines of birds that after death the muscular
walls were still alkaline.

Myolimmatin.—ThQw.^ heemoglobin is the pigment of the red
muscles, MacMunn*^ considers that the specific pigment of ordinary
muscle is myohfematin, one of the most widely distributed of the colour-
ing matters which he has described under the name histolucmatins. The
histohaimatins have only been observed by the spectroscope ; they have
not been separated out by chemical processes. They often occur in
animals that possess no hcemogiobin. As they undergo changes in their
absorption bands, by oxygenation and reduction, it is believed that they
are respiratory in function. The spectrum of these substances is some-
what like that of htemochromogen ; and Levy, working under Hoppe-
Seyler,'^ has gone so far as to say that myoha?matin is hcTemochromogen
produced by the methods used to render the muscle transparent. The
resemblance is not absolute, but is specially close in what MacMunn calls
modified myohaematin. This is produced by artificial gastric digestion ;
or it can be obtained in the following way : — The mviscle is chopped finely
and covered with ether for some days. A yellow lipochrome derived from
the fat between the muscular fibres^ passes into solution, and below this
floats a red juice, which on filtration gives the spectrum in question.

Until myohfematin and the other histoh?eniatins are examined
by methods other than spectroscopic, it is impossible to pronounce
positively on the point of dispute between MacMunn and Levy. The
fact that in the last experiment described, the muscles, even if they are
full of blood, yield no longer any haemoglobin, points to haemoglobin
as the source of the myohajmatin ; whether this substance can be pro-
duced in the muscles intra vitam must be left to the future to decide.^

The extractives of muscle. — These are — (a) Nitrogenous, namely,

1 Boruttau, Ztsclir. f. fhysiol. Chem., Strassburg, Bd. xviii. S. 513.

" Quoted by Hoppe-Seyler, "Physiol. Chem. ,"S. 669.

^Bernstein (Kiihne's "Lehrbuch," S. 332) found the actively contracting muscles of
Anodon acid. ' * "Lehrbuch," Bd. iii. S. 73.

•'' Monatsh. d. k. prcuss. Akad. d. IVissensch. zu Berlin. 1859, S. 312.

" Phil. Trans., Loudon, 1886 ; Journ. Physiol., Cambridge and London, vol. vii.

■^ Ztschr.f. jyhysiol. Chem. , Strassburg, Bd. xiii. MacMunn's reply is in the same vol., S. 497.

^ Halliburton, Journ. Physiol., Cambridge and London, vol. vii. p. 325.

^ K. Morner {Nord. med. ArJc., Stockholm, Festband, 1897) states that muscle pigment is
hsemoglobin which spectroscopically shows slight differences from that obtained from blood.



loo THE CHEMISTRY OF THE TISSUES AND ORGANS.



creatine, creatinine, xanthiae, hypoxanthine, carnine, carnic acid, nric
acid, urea, taurine, and inosinic acid. (&) Non-nitrogenous, namely, fats,
glycogen, inosite, dextrose, and lactic acids.

Creatine and creatinine. — Creatine can be crystallised out by

evaporating aqueous extracts
of meat from which proteids
and salts have been previously
removed ; on heating it with
mineral acids it is converted
into creatinine. The relation-
ship of these two substances
is shown by the following
equation : —
C4H9N3O2— H^O - C.H.NsO

(creatine) (creatinine)

According to Voit,^ the
quantity of creatine in the
voluntary muscles varies from
0-2 to 0-3 per cent. This
increases during starvation.^




Fig. 13. — Creatine crystals. — After Kiiliue.



Involuntary (cardiac and plain) contains less than voluntary muscle.^

The compound with zinc chloride w^hich creatinine forms (Fig. 15) has
been generally used for isolating it from urine, and other places where it

occurs. My own experience with

m



this method has shown that for
quantitative purposes it is most
uncertain ; and this no doubt ac-
counts for the different results
obtained by different observers.
Thus Neubauer denies the exist-
ence of creatinine in muscle
altogether; Yoit, Sarokin,* and
Monari^ say that it increases
during muscular activity, while
ISTawrocki^ states that it does
not. Much more certain results
are obtained by the use of G. S.
Johnson's method, in which he
precipitates the creatinine as a
compound of mercury.'^ This
method, which has received the




Fig. 14. — Creatinine crystals. — After Kiilme.



powerful recommendation of Hoppe-Seyler,^ may be used to identify
creatinine when it is present in very small quantities, as in the blood.^
The microscopic appearance of the precipitate is show^n in Fig. IG. By

1 Ztschr.f. Biol., Mlinchen, Bd. iv. S. 77.

- Demant, Ztsclir. f. pliysiol. Clicm., Strassbnrg, Bd. iii. S. 387.

^ Voit, loc. cit. ; Lelimann, " Lehrbucli," Bd. iii. S. 73.

■* Virchoiv's ArcMv, Bd. xxvii. ^ Gazz. chim. ital., vol. xvii. p. 367.

^ Centralhl. f. d. med. Wisscnsch., Berlin, 1865, S. 417.

■^ Proc. Rvij. Soc. London, vol. xlii. p. 365 ; xlii. p. 493 ; 1. p. 28. Johnson
here points ont that there are several isomeric varieties of creatinine, differing in redncing
power, etc. In his process he is careful to employ no heat; otherAvise the creatinine is
transformed into a non-reducing variety, or even may be changed into creatine.

* "Handbuch. d. phy.siol. cheni. Analyse," 1893, 7th edition, S. 142.

^ Colls, Journ. Physiol, Cambridge and London, 1896, vol. xx. p. 107.



THE EXTRACTIVES OF MUSCLE.






this means Johnson showed that creatinme (a different creatinine from
urinary creatinine) is more abundant in muscle than creatine, which
is usually almost entirely absent. This unexpected result has been
confirmed by Kemmerich/ Creatinine is readily changed into creatine
by the action of putrefactive micro-organisms.

Xanthocrcatinine (CgHjoN^O), critsocreatinine (CgHgN^O), ami^hicrea-
tine (GqR^qN^O^), and pseudoxantMne (C4H5N5O) are leucomaines stated
by Gautier ^ to be present in small quantities.

Xanthine, hifpoxanthinc, and uric acid are found in small quantities
only; the numbers given are as follows : — xanthine, 0'0026 per cent. ;^
hypoxanthine, 0-022-0-026 ;'^ uric acid, traces.^ Uric acid is more
abundant in the muscles of reptiles (alligators). The crystalline forms
of some of the compounds of xanthine
and hypoxanthine are given in Fig. 17.

C amine- is a crystalline base
(C.HgN.Oa+H.p), originally found by
Weidel'' in large quantities (1 per
cent.) in American meat extracts, but
since found in the flesh of many
animals.'^ It is probably closely re-
lated to the members of the uric acid
group just mentioned.

Urea. — It is generally stated that
muscle contains little or no urea.
This statement is chiefly due to the
fact that it was until recently a
matter of difficulty to separate
urea, when only present in small
quantities, from other nitrogenous bases. In some animals, however,
the muscular tissue contains a fairly large amount of urea. This is
the case with the muscles of arthropods.^ Stadeler and Frerichs^
were the first to discover that the organs, including the muscles,
of Selachian fishes are rich in urea. This was confirmed in the case
of Selachian embryos by Krukenberg,^^ and more recently in the
adult animals by Schroder.^^ In two varieties of dog-fish, the
mean percentage of urea in the blood was 2'61, in muscle 1"95, and
in liver 1-36. Schroeder explains this by the fact that the kidneys are
sluggish in these animals. By a new method, Schondorff^^ has been
able to satisfactorily establish the existence of a small quantity of
urea in the muscles of mammals ; Kaufmann ^^ gives the percentage




Fig. 15.-



-Creatiue-zinc chloride crystals.
— After Klilme.



^ Kemmerich, Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xviii. S. 409.

^ Jahresh. i'l. d. Forfschr. d. Thier-Ghem., Wiesbaden, Bd. xxii. S. 335.

" Scherer, Ann. d. Chem., Leiyizig, Bd. cvii. S. 314.

■^ Neubauer, Ztschr. f. anal. Chem., Wiesbaden, Bd. vi. S. 33.

■' Meissner, Ztschr. f. rat. Med., Leipzig, Bd. xxxi. p. 144.

" Ann. cl. Ghcm., Leipzig, Bd. clviii. S. 353.

'' Krukenberg and Wagner, Sitzungsh. d. phys.-med. Gesellsch. zu Wilrzburg, 1883, No. 4,
See also Jahresh. u. d. Fortschr. d. Thier-Ghem., Wiesbaden, Bd. xi. S. 340.

^ Krukenberg, Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg, 1881, Bd. iv. S. 33 ;
" Vergleich. physiol. Vortrage," 1886', S. 313.

^ Journ. f. prakt. Ghem., Leipzig, 1858, Bd. Ixxiii. S. 48 ; ibid., Bd. Ixxvi. S. 58.
10 "Vergleich. physiol. Vortrage," 1886, S. 314.

'^'■Ztschr./. 2)hysiol. Ghcm., Strassbnrg, 1890, Bd. xiv. S. 576; Krukenberg, Gentralbl.
f. d. med. JVissensch., Berlin, 1887, No. 25.

^'■^ Arch.f. d. ges. Physiol. , Bonn ,1895, Bd. Ixii. S. 332. For the metliod employed, see ibid. , S. 1 .
^^ Arch, de xihysiol. norm., etpath., Paris, Si^r. 5, tome vi.



I02 THE CHEMISTRY OF THE TISSUES AND ORGANS.

as 0'027 to 0'07. On the other hand, it must he stated that such
an experienced chemist as Nencki ^ is still unahle to discover any
urea in muscle.

Taurine, is fomid in the muscles of horses, fishes, and molluscs. In
fishes Limpricht^ found 1-06 per cent.

Glycocine is found to the extent of 0-39 to 0"71 per cent, in the non-
striated muscles of molluscs.^

Protic acid is an acid of doubtful nature, described by Limpricht in
fishes' muscles.

Inosinic acid (C10H14N4O11) was first described by Liebig, and




Fig. 16. — Spherical compoiiud of mercury aud creatine. —
After G. S. Johnsou.

estunated (0-005 to 0-02 per cent.) by Creite.^ According to Frankel,^
it is closely related to carnic acid, to be immediately described.

Lecithin and its decomposition products are present in small
quantities, and are probably derived from the nerves supplying the
muscle.^ Small quantities of cholesterin are found as well.

Carnic acid (Flcischsdure) is the name given ])j Siegfried '^ to a con-
stituent of muscle, the discovery of which is of great importance. He
first prejjared it from muscle extracts by means of ferric chloride ; the
compound so obtained is called carniferrin ; this contains phosphorus as

^ Neucki and Kowaski, Arch. f. ex^er. Path. v.. Pliarmakol., Leipzig, 189.5, Bd. xxxvi.
S. 39.5.

- Ann. d. Cheni., Leipzig, Bd. cxxvii. S. 185 ; cxxxiii. S. 300.

■'Chittenden, ibid., Bd. clxxviii. S. 266.

* Ztsehr.f. rat. Med., Leipzig, Bd. xxxvi. S. 195.

■' " Zur Kenntniss der Zerfallproducte des Eiwei.sses," Wien, 1896.

" Hoppe-Scyler, "Physiol. Chem.," S. 647.

"^ Bcr. d. dcidsch. chem. Gcscllsch., Berlin, 1894, Bd. xxvii. S. 2762 ; Ztschr. f.ithysiol.
Clbcvi., Strassburg, Bd. xxi. S. 360.



THE EXTRACTIVES OF MUSCLE.



103



well as iron. By means of baryta water, carnic acid (C10H15N3O5) was
separated out from it. In muscle, this acid is combined with phosphorus
as phospho -carnic acid. Garnic acid itself is identical with antipeptone.
This discovery itself shows that our views concerning the hemi- and
anti-products of digestive proteolysis will need revision. Carnic acid
is a comparatively simple substance, of low molecular weight, and of
acid reaction. It is free from sulphur, and gives most of the proteid




Fig. 17. — Compounds of xanthine and hypoxanthine, by means of which these substances
may be isolated and identified. — After Kiihne.

a. Hypoxanthine silver nitrate, CgH^Nj^O.AgNOg.

b. Hypoxanthine nitrate, CgH^N^O. HNO3.

c. Hypoxanthine hydrochloride, CjH^N^O. HCl.

d. Xanthine silver nitrate, C^H^N^O., AgNOg.

e. Xanthine nitrate, CsH^N^O^. HNO3.

*'. Xanthine hydrochloride, CgH^N^OoHCl.



tests ; it does not give Millon's reaction. This discovery will no doubt
form an important clue in the problem of proteid constitution. This
announcement of Siegfried's has been fully confirmed by Balke,i
who has prepared many compounds and derivatives (oxycarnic acid,
C30H41N9O15; oxylic acid, Cj^gHggN^Og; and various crystalhne metallic
salts of these acids), and has devised a method for its estimation.^ It

'^ Ztschr. f. iihysiol Chem., Strassburg, 1896, Bd. xxii. S. 248.
^ Balke and Ide, ibid., Bd. xxi. S. 380,



I04 THE CHEMISTRY OF THE TISSUES AND ORGANS.

has been further confirmed by Frank el/ who finds that pm-e ampho-
peptone is also sulphur-free.

Phosphocarnic acid has a complicated molecule; it yields on
decomposition carnic acid, carbonic anhydride, succinic acid, sarcolactic
acid, and a strongly reducing carbohydrate. Siegfried compares it to
nuclein ; but nucleins yield proteid on decomposition ; phosphocarnic
acid yields carnic acid (antipeptone) instead ; he suggests the term
nucleoli for it. The percentage of this substance in human muscle is
0"l-0"2. In new-born children the muscles contain less (0 to 0'06 per
cent.2

A phosphocarnic acid is also found in milk, but differs from that in
muscle by yielding fermentation lactic acid instead of sarcolactic acid
on decomposition.^

Krliger * has found that on hydrolysis and simultaneous oxidation by
means of ferric chloride, phosphocarnic acid gives off carbonic anhydride ;
no other substance in muscle extracts does this. He therefore looks
upon it as the material in muscle which during muscular activity gives
off carbonic anhydride without using up oxygen. This is a conclusion
that requires serious consideration and renewed research before it can
be accepted, but it is another indication of the importance of Siegfried's
work.

We now pass to the non-nitrogenous extractives : —

Glycogen. — This substance may be extracted from muscle by hot
water ^ ; or by dilute potash ^ ; the latter reagent effects a much more
thorough extraction. Cramer,'^ using Kiilz's method, fomid that different
groups of muscles contain varying amounts of glycogen, but that corre-
sponding muscles of the two sides of the body contain the same amomit.
In the heart, glycogen is unequally distributed in the different regions
(Cramer). The average percentage of glycogen in fresh heart muscle
is, however, about the same as in voluntary muscle, though it dis-
appears after death (being converted into sugar as in the hver) more
rapidly than in skeletal muscle.^ Glycogen also occurs in other
involuntary muscles.^

The glycogen in muscle during life varies in quantity. The following
are the principal causes of variation : —

1. Starvation. — The muscle glycogen disappears during inanition, but
much more slowly than the hepatic glycogen.^" Luchsinger^^ stated
that the glycogen of the heart muscle disappears still less quickly, but
Aldehoff (using Kiilz's method) could not confirm this.

^' Loc. cU.

I M. Miiller, Ztschr. f. physiol. Chan., Strassburg, 1897, Bd. xxii. S. 56L

•" K. Wittmaack [ibid., S. 567) gives- the percentage of nucleoli in human milk as 0'124 ;

in cows' milk, 0'056, and in goats' milk, O'll. Blumeuthal {Virchow's Archiv, Bd. cxlvi.

S. 6.5) gives the percentage in cows' milk as 0'05.

* Zlschr. f. pliysiol. Ghcm., Strassburg, 1896, Bd. xxii. S. 95.

5 Brlicke, Sitzungsb. d. h. Akad. d. JFissensch., Wien, 1871, Bd. Ixiii. Abth. 2, S. 214 ;
Nasse, Arch. f. d. ges. Physiol., Bonn, Bd. ii. S. 97.

" Abeles, Med. Jahrb., Wien, 1877, S. 551 : Ktilz, Ztschr. f. Biol., Miinchen, Bd. xxii.
S. 161. See also Schmelz, ibid., Bd. xxv. S. 180.

"^ Ibid., Bd. xxiv. S. 67.

* Boruttau, Ztschr. f. physiol. Clievi., Strassburg, Bd. xviii. S. 51.3.

^ In the stomach, Briicke, loe. cit. ; in the plain muscles of gastropods, Chittenden,
Ann. d. C/ievi., Leipzig. Bd. clxxviii. S. 266 ; Bizio, Atti. r. 1st. Veneto di sc, Ictt. et arti,
1866, S(ir. 3, tome i.

^" Weiss, Silzunqsh. d. k. Akad. d. JFissensch., Wien, Bd. Ixiv. ; Aldelioff, Ztschr. f.
Biol., Munclien, Bd. xxv. S. 1.37.

" Dissertation, Zurich, 1875.



THE EXTRACTIVES OF MUSCLE.



105



2. Work. — During work the glycogen disappears, l^eing perhaps
transformed into sugar and the products of its combustion, of which
lactic acid may be an intermediate one^ (Weiss, Manchd, Monari).
This loss of glycogen is shown by numerous analyses, of which the
following from Manche will serve as a type : —





Percentage of Glycogen in
Limb at rest.


Percentage of Glycogen in

opposite Limb, which was made

to contract for 23-65 minutes.


Percentage loss of Glycogen
in Tetanised Limb.


1

2
3


0-1277
0-2287
0-2267


0-114

0-1942

0-1917


12-76
15-09
15-44



3. Removal of liver. — Minkowski,^ Laves,^ and Schmelz ^ find that
after removal of the liver the muscle glycogen rapidly diminishes. Some
observers,^ however, consider that the muscles have a glycogenic
function apart from that of the liver.

4. Cutting the nerve of a muscle causes an accumulation of glycogen
in the muscle so paralysed.^

5. Cutting the tendon of a muscle produces the same effect.''

6. Ligature of the artery of a muscle leads to a decrease in its
glycogen, especially if oedema follows the operation, the accumulated
lymph leading to saccharification (Chandelon, Manche).

Sugar. — During life the sugar in muscle is at a minimum ; it
increases after death as the glycogen disappears. The sugar is not
maltose, as Nasse ^ supposed, but dextrose, as Meissner ^ suggested ; the
work of Panormoff '° with the phenylhydrazine reaction has placed this
beyond doubt. . Small quantities of dextrin are found as an intermediate
pro duct. ^^

Inosite. — The occurrence of this substance in voluntary muscle
has been noted by Soberer ^^ and Limpricht; in unstriated muscle by
Lehmann ; and in heart muscle, where it is more abundant than in
skeletal muscle, by Boruttau.^^

Fat. — This is always obtained from muscle, though whether any
occurs in the true muscular substance apart from the entangled
adipose tissue, it is difficult to say. Dormeyer ^* finds that after muscle
has been subjected to preliminary gastric digestion, ether extracts 8-5

^ Weiss, loc. cit. ; Mancli^, Ztschr. f. Biol., Miinchen, Bd. xxv. S. 163 ; Monari, Chcm.
Centr.-Bl, Leipzig, 1889, Bd. ii. S. 372.

"^ Arch. f. expcr. Path. %. Fharmakol., Leipzig, Bd. xxiii. S. 139.

^ Inaug. Diss., Konigsberg, 1886.

^ Ztschr. f. Biol., Mltnclien, Bd. xxv. S. 180.

^ Prausnitz, Ibid., Bd. xxvi. S. 377 ; Schmelz, loc. cit.

^ Chandelon, Arch. f. d. ges. Physiol., Bonn, Bd. xiii. S. 626 ; Manche, loc. cit.

'' E. Krauss, Virchow's Archiv, Bd. cxiii. S. 315.

^ "Zur. Anat. u. Physioh der quergestreiften Muskel," Leipzig, 1882.

^ Nachr. v. d. k. Gcsellsch. d. JVisscnsch. «. d. Georg- Aug. -Univ., Gbttingen, 1861, S. 206 ;
1862, S. 157.

^^ Ztschr. f. physiol. Chem., Strassburg, Bd. xvii.

■^^ Nasse, loc. cit. ; Liinpiicht, loc. cit.

^^ Ann. d. Chem., Leipzig, Bd. Ixxvii. S. 322.

'^^ Ztschr. f. 2')hysiol. Chem., Strassbnrg, Bd. xviii. S. 513.

^* Arch./, d. ges. Physiol., Bonn, 1896, Bd. Ixv. S. 90,



^ THE CHEMISTRY OF THE TISSUES AND ORGANS.
io6

, nt. more of the total fat obtainable : without such preliminary

J- Dn, extraction with ether is useless for quantitative purposes. E.

■n ^ ?cnow ^ believes that the fat which is thus soluble in ether with

^,-ncult7 is a real constituent of the muscle plasma, and states that it is

richer in volatile fatty acids than that from the surrounding connective

tissues. For "Adipocere," see p. 20.

Lactic acids. — Among the oxypropionic acids with the empirical
formula CjHgOg, one called hydracryhc acid, or ethylene lactic acid, CHg
(0H).CH2-C00H, is not found in the body. Small quantities of this
material were formerly described ^ as occm-ring in muscle extracts, but
this is not the case ; the acid mistaken for it was acetyl-lactic acid
H3CH(C2H30,)COOH.^

The remaining lactic acids are stereochemical isomerides of
ethylidene lactic acid. They are three in number, and differ in optical
activity, and in the solubility, optical activity, and amomit of crystallisa-
tion water in their zinc, calcium, and lithium salts.'^

Their- formula is CH3.CH(0H).C00H. The differences between
them are due, according to the theory of Bel and Van't Hoff, and as the
expression stereochemical implies, to the space relationships of the atoms.

The three isomerides are —

{a) The optically inactive acid. This is the ordinary fermentation
lactic acid, wliich occm's in milk when it turns sour ; it has l:)een found
in small quantities in muscle,^ in the grey matter of the brain,^ and in
some cases of diabetic urine. Its most characteristic salts are —

Zinc lactate Zn.{CJi.,(}o).2 + SH^O ; soluble in fifty-three parts of water
at 15° ; in six parts at 100° C. ; almost insoluble in alcohol.

Calcium lactate, Ca(C3H.03)2 + 511^0 ; soluble in 9*5 of cold, and in
all proportions in boiling water. Insoluble in cold alcohol.

Qj) Dextrorotatory lactic acid. — This is paralactic, or sarcolactic
acid. This is the lactic acid ^:>ar coxellence of muscle.'^ • It is found in
the blood,^ particularly after muscular activity.^ It is found in the
urine after muscular activity,^*^ dming diminution of oxidation processes,^^
in phosphorus poisoning, and after extu-pation of the hver.^^ It is found
as noted when we considered them, in many organs and tissues after
death. Its Ijest known salts are —

Zinc sarcolactate, Zn{GoyS.,fio)., + 211.20. Soluble in IT'S parts of water at
15° C, and in 96 '4 parts of boiling 98 per cent, alcohol.

^Arch.f. d. ges. Physiol., Bonn, Bd. Ixv. S. SI.



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