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

Text-book of physiology; (Volume v.1) online

. (page 4 of 147)
Online LibraryE. A. (Edward Albert) Sharpey-SchäferText-book of physiology; (Volume v.1) → online text (page 4 of 147)
Font size
QR-code for this ebook


additional 0"75 per cent, of fat.

The fats are compounds of fatty acids with glycerin, and are termed
glycerides or glyceric ethers. The fatty acids form a series of acids derived
from the monatomic alcohols by oxidation ; thus —

From methyl alcohol (CH3HO) formic acid (H.COOH) is obtained.

From ethyl alcohol (C^.H^HO) acetic acid (CH3COOH) is obtained, and so on.

^ Comi^t. vend. Accul. d. sc, Paris, 1887, tome civ. pp. 225, 297, 1719, 1853. For colour
reactions of iuosite, see Scherer, Ann. d. Cheon., Leipzig, 1852, Bd. Ixxxi. S. 375 ; Gaulois,
Ztsclir. f. anal. Chem., Wiesbaden, 1865, Bd. iv. S. 264 ; Seidel, Bcr. d. deutsch. cJicm.
Gesellsch., Berlin, 1887, Bd. xx. S. 320.

2 Arch. f. d. gcs. Physiol., Bonn, 1895, Bd. Ixi. S. 341 ; 1896, Bd. Ixv. S. 90 ; F. N.
Sclmlze {ibid., Bd. Ixv. S. 299 ; 1897, Ixxii. S. 145) has used the same method for the
extraction of the fat of blood, and numerous organs.
VOL. I. — 2



1 8 CHEMICAL CONSTITUENTS OF BODY AND FOOD.



Or, in general terms —
From the alcohol with



formula C„Ho„.i.HO the acid with formula



^n-iHon-i-CO.OH is obtained. The sixteenth term of this series has the
formula Cj5Hpj.CO.OH, and is called palmitic acid; the eighteenth has the
formula Cj-H.^.CO.OH, and is called stearic acid. Each acid, as will be seen,
consists of a radicle, Cn_jH2n iCO, united to hydroxyl (HO).

Oleic acid, however, is not a member of this series, but belongs to a some-
what similar series of acids known as the acrylic series,^ of which the general
formula is Cn-iH^n-sCOOH. It is the eighteenth term of the series, and
its formula is Cj-H33.CO.OH.

Glycerin or glycerol is a triatomic alcohol, G^-J{OW).. — i.e. three atoms of
hydroxyl united to a radicle glyceryl (C3H5).

The hydrogen in the hydroxyl atoms is replaceable by other organic radicles.
As an example, take the radicle of acetic acid, called acetyl (CHo.CO). The
following formulae represent the derivatives that can be obtained by replacing
one, two, or all three hydroxyl hydrogen atoms in this way : —



[OH

OH

[oh

(glycerin)



CoH



C,H



OH
OH
^[O.CH,.CO

(moiioacetin)



C3H5-



OH

O.CH3.CO

O.CH3.CO



(diacetin)



[O.CHo.CO

C3H 'o.ch;.co
to.CH3.co

(triacetin)



The contents of the fat cells of adipose tissue in man are fluid during
life, the normal body temperatm'e being higher than the melting point
of the mixture of fats found there ; but this is not the case in all
(even warm-blooded) animals, for beef fat melts at about 45° C, and
mutton fat at a still higher temperature. Human fat consists of
the three glycerides — palmitin, stearin, and olein. They differ in
chemical composition, melting point, and solubilities. Olein melts at
-5" C, palmitin at 45° C, and stearin at 53° to 66° C. It is thus olein
which holds the other two dissolved at the body temperature. All are
soluble in hot alcohol, ether, and chloroform, but insoluble in water.

The proportion in which these fats are mixed differs in different
animals ; in cold-blooded animals olein is much more abundant than in
warm-blooded animals. Human fat contains from 67 to 80 per cent,
of olein. Mixed with these neutral fats, there is generally a small
amount of free fatty acids.

Fats are also found in the vegetable kingdom, especially in seeds and
fruits, but in many cases in the roots also.

Stearin, palmitin, and olein ought more properly to be called tristearin,
tripalmitin, and triolein respectively. Each consists of glycerin, in which the
three atoms of hydrogen in the hydroxyls are replaced by radicles of the fatty
acid. This is represented in the following formulae. : —



Acid.


Radicle.


Fat.


Palmitic acid C15H31.COOH
Stearic acid . C17H35.COOH
Oleic acid . CiyHjs.COOH


Palmityl Ci,H3i.C0
Stearyl. Ci^H^.-CO
Oleyl . C,,H33.C0


Palmitin C3H5(0C,5H3i.C0)3
Stearin . GJl^{OC^^Yi.a^.CO)^
Olein . G3H5(0CiyH33.C0)3



1 Acrylic acid itself (C3H4O2
aldehyde of allyl alcohol.



is obtained by the oxidation of acrolein (C3H4O), the



THE FATS. 19

Under the influence of superheated steam, ninieral acids, and in the
body by means of certain ferments (for instance, the fat-sphtting
ferment of the pancreatic juice), a fat comljines witli water and s])lits
into glycerin and the fatty acid. The following equation represents
what occurs in a fat, taking tripalmitin as an example : —

C3H,(O.Ci,K3iCO)3-f 3H2O = C3H,(OH),+3Ci,H,iC( ).0H

(palniitin — a fat) (glycerin) ([talmitic acid — a

fatty acid)

Scqionification. — In the process of saponification much the same sort
of reaction occurs, the final products jjeing glycerin and a compound of
the base with the fatty acid, which is called a soap.

Suppose, for instance, that potassium hydrate is used, we get —

C3H,(O.Ci5H,,iCO)3+3KHO = C3H,(OH)3+3Ci5H3iCO.(3K

(palniitin — a fat) (glycerin) (potassium palmitate

— a soap)

To separate the neutral fats from one another, they have always to be
saponiiied ; this can be accomplished by potassium hydrate, or still
better by sodium alcoholate (Kossel, Obermiiller, and Krliger).^ On
evaporation of the alcohol, the soaps are dissolved in water, and pre-
cipitated by sugar of lead ; the lead compound of oleic acid is solul:)le in
ether ; the remaining soaps are treated with soda on the water Ijath,
dried, dissolved in alcohol, and separated by fractional precipitation with
barium acetate or barium chloride.

In the decomposition of fat, propionic, acetic, and formic acids may
be found, which are absent from the fat in the fresh condition. This
occurs when the fat becomes rancid, and is also produced by putre-
factive organisms in the alimentary canal. The process is one of
oxidation, and the way in which lower terms of the series are produced
may be illustrated by the following equations : —

CgHoO.-f O3 = C,H40.,+C024-H,0.

(propionic acid) (acetic acid)

C2H,02+03=CH20,+C02+H20.

(acetic acid) (formic acid)

2CHA+02=2C02-1-2H20.

(formic acid)

Emulsifieation. — Another change that fats undergo in the body is very
different from saponification. It is a physical rather than a chemical
change ; the fat is broken up into very small globules, such as is seen in
the natural emulsion — milk.

The fats of milk resemble in a general way those of adipose tissue,
but there is a considerable admixture of glycerides lower in the series
(see " Milk ").

The fats of marrow are also like those of adipose tissue. As will be
noticed in the table on p. 17, bone marrow is the tissue which is richest
of all in fat.

Eylert ^ described a new fatty acid in the marrow of oxd3one which he
called medullic acid, but this was shown by Mohr^ to be only stearic acid.

^ Numerous pajiers in vols, xiv., xv. , and xvi. of Ztschr. f. jjhysiol. C'hcm., Strassburg.

- Vrtljschr. f. prakt. Pharmakol., Bd. ix. S. 330.

^ Ztschr. f. physiol. Chem., Stras,sburg, 1890, Bd. xiv. S. 390.



20 CHEMICAL CONSTITUENTS OF BOD Y AND FOOD.

Molir gives the proportion of the acids in marrow fat as — pahnitic acid, 22 ;
stearic acid, 10; and oleic acid, 63 per cent.

Among the exceptional forms of fat are the following : —

Spermaceti, obtained from the sperm wliale. This fat sets into a solid,
white crystalline mass, melting at from 30° to 50° C. Its chief constituent
is the palmitate of cetyl alcohol, or ethal (CmHgsOH). This alcohol is the
one from which palmitic acid is derived in the same way as acetic acid
is derived from ethyl alcohol. Spermaceti contains also small quanti-
ties of compounds of lauristic, myristic, and stearic acids, with the
radicles of the alcohols lethal (Ci9H„50H), methal (C14H29OH), and
stethal (CisHgyOH).

Beeswax contains three chief constituents : —

(1) Myricin ; this is its principal constituent ; it is the palmitate of
myricyl alcohol (CsoHgiCJH) ; (2) Cerotic acid (C27H-,i02) ; and (3) Cerolein,
which is probably a mixture of several substances.

Chinese toax is chiefly the cerotic acid compound of cerotyl alcohol
(C2,H3,OH).i _

Aclipocere is the name given to a waxy substance which replaces the
muscular tissue in corpses buried in damp soil, or which have been
allowed to remain in water some time after death. It consists chiefly
of the calcium soaps of palmitic and stearic acids, and m some cases of
acid ammonium soaps also.^ Hoppe-Seyler ^ considered that the change
is the result of a ferment action.

LiPOCHEOMEs, Lecithin, Cholesteein.

Lipochromes. — This name is given to the pigments which occur in
fat and fatty tissues. They are mostly yellow or yellowish red. They
include the pigment of the blood serum (serum lutein) and of the corpus
luteum ; the chromophanes or coloured oil globules of the retinal cones ;
the yellowish pigment in butter, adipose tissue, and egg-yolk ; tetronery-
thrin, a reddish pigment, found in many invertebrates ; and several
vegetable pigments, such as carrotin, which is found in carrots and
tomatoes. The lipochromes have been separated by their various
solubilities after saponification ; they give various colour reactions, such
as a greenish-blue colour with iodine and sulphuric acid, and a green
colour with nitric acid; they show absorption-bands towards the
violet end of the spectrum, and especially in the region of the F line.

Nothing is known about their chemical constitution ; carrotin, which
has been examined more fully than the others, has been assigned the
formula C18H24O by Husemann, and C26H3g by Arnaud.^

1 On these rarer forms of fat and wax, see Liebermann, Ber. d. deutsch. chem. GescUsch.,
Berlin, 1885, Bd. xviii. S. 1975.

2 Quain, Med.-Chir. Trans., London, 1850, p. 141; Virchow, Vcrhandl. d. phys.-med.
GescUsch. in JVilrzhurg, Bd. iii. ; Wethcrill, Joiirn. f. frald. Chem., Leipzig, Bd. Lwiii. S.
26 ; K. B. Lehmann, Cantralbl. f. Agric. Chem., Leipzig, 1889, S. 66.

'^ "Physiol. Chem.," Strassburg, S. 119. According to some authors, its formation is
brought about by micro-organisms (Jacobsthal, Arch. f. d. qcs. Physiol., Bonn, 1893, Bd.
liv. S. 499.

^ The principal papers on lipochromes are the following : — On lutein — Thudichum,
Centralhl. f. d. med. Wissensch., Berlin, 1869, Bd. vii. S. 1. On colour reactions of
luteins — Thudichum, loc. cit. ; Piccolo and Lieben, Gior. de sc. nat. ed. econ., Palermo,
vol. ii. p. 258; Caprarnica, Arch. f. Physiol., Leipzig, 1877, S. 283.; ScliAvalbe,
" Handb. d. ges. Augenheilkunde," Leipzig, 1874, Bd. i. S. 414. On chromophanes
— Kiihne and Ayres, Journ. Physiol., Cambridge and London, 1878, vol. i.
p. 109 ; Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg, Bd. i. Heft 4. On



LECITHIN. 21

Lecithin is a complex fat of wide distriljution. It is a constant
constituent of protoplasm, and is found both in the animal and
vegetable ^ world. In the animal tissues, it is found principally in
the brain and nervous tissues, where it is probably a decomposition
product of a more complex substance originally called protagon by
Liebreich "^ (see section on " Chemistry of jSTervous Tissues ") ; in yolk
of egg;^ and in blood corpuscles.^ Lecithin is found in all organs
composed of cells, and also in certain secretions, namely, semen, bile,
and milk.

Lecithin is a yellowish white, waxy, hygroscopic solid, soluble in
ether and in alcohol; it swells and forms a kind of emulsion with
water. When ignited it bm-ns and leaves a residue of metaphosphoric
acid. Its most important compounds are those of its hydrochloride
with platinum chloride (C^4lIgoN'P09Cl)2+PtCL, and with cadmium
chloride which has a corresponding formula.^

Montgomery ^ showed that when water, glycerin, and other reagents
were added on a microscopic sHde to impure lecithin (or protagon, as he
termed it), prepared from egg-yolk, snake-like forms shoot out, bending
and cm^ing and even sunulating nerve fibres or nerve cells. On
cooling a solution of lecithin in alcohol, it separates out in crystal-
line clumps. On decomposition by alkalis, it yields glycero-phosphoric
acid, a fatty acid, and an alkaloid choKne.

Gholine is an ammonium base, and has the following constitution: —

^\ CH.,— CHoOH \ = C5Hi3N"0„
lOH ^ J

It is therefore trmiethyl-oxyethyl-ammonium hydroxide ; its name
is derived from the fact that it was first separated from the lecithin of
the bile. Its synthesis was accomplished by Wurtz'' from ethylene

tetronerythrin — Wurm, Ztschr. f. icissensch. ZooL, Leipzig, 1871, Bd. xxxi. S. 535 ;
Merejkowski, Comj^f. rend. Acad. d. sc, Paris, 1881, tome xciii. p. 1029 ; MacMunn, F7'oc.
Birmingham Phil. Soc, vol. iii. p. 351 ; Froc. Roy. Soc. London, 1883, No. 22fi, p. 17 ;
Halliburton, Journ. Physiol., Cambridge and London, 1884, voL vi. p. 324 ; Krukenberg,
Centralbl. f. d. med. TVissensch., Berlin, 1879, Bd. ix. S. 705. On serum lutein —
Krukenberg, Sitzungsb. d. Jenaisch. Gesellsch. f. Med. u. Katuric, 1885; Halliburton, Journ.
Physiol., Cambridge and London, 1885, vol. vii. p. 324. On saponification of lipoehromes
— Klilme. loc. cit. ; Maly, McniatAh. d. Chem., Wien, 1881, Bd. ii. S. 351 ; Bein, Jjer. d.
deiitsch. chem. Gesellsch., Berlin, 1890, Bd. xxiii. S. 204. On carrotin — Husemann, Ann. d.
chem., Leipzig, Bd. cxvii. S. 200 ; Arnaud, Com'pt. rend. Acad. d. sc, Paris, tome cii.
p. 119; civ. 1293. Newbiggin, "On Crustacean Pigments," e/bzfrji. Physiol., Cambridge
and London, 1897, vol. xxi. p. 237.

^ On the subject of lecithin and choline in vegetable oils, etc., see Heckel and
Schlagdenhauffen, Compt. rend. Acad. d. sc, Paris, tome ciii. p. 188 ; Jacobson, Ztschr. f.
physiol. Chem., Strassburg, Bd. xxiii. S. 33 ; Schulze, ibid., Bde. xi. S. 365 ; xii. S. 441 ;
xvii. S. 204 ; J. Stoklasa, Per. d. deutsch. chem. Gesellsch., Berlin, 1896, Bd. xxix. S. 2761.

" Ann. d. Chem., Leipzig, Bd. cxxxiv. S. 29.

' Gobley, Journ. de yliarm. et chim., Paris, tomes xi., xii., xvii., xviii. ; Parke,
Hoppe-Seyler's "Med. Chem. Untersuch.," Berlin, Heft 2, S. 213 ; Hoppe-Seyler, ibid., S.
215 ; Diaconow, ibid., S. 221 ; Centralbl. f. d. med. JFisscnsch., Berlin, 1868, S. 2.

■* Gobley, Journ. de phai'vi. et chim., Paris, tome xxi. p. 250 ; Hermann, Arch.
f. Anat. %(,. Physiol., Leipzig, 1866, S. 33 ; Hoppe-Seyler, "Med. Chem. Untersuch.," Berlin,
"Heft 1, S. 140 ; Jiidell, ibid.. Heft 3, S. 386.

^ The formation of these compounds enables one to prepare lecithin in a pure form, the
metal being subsequently got rid of by sulphuretted hydrogen.

^ "On the Formation of So-called Cells," London, 1867.

' Ann. d. Chem., Leipzig^, 1868, Supplement, Bd. vi, S. 116 and 197 ; see also Baver,
ibid., Bd. cxl. S, 306.



2 2 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

oxide (C2H4O), trimethylamine N(CH3)3, and water. It was at one time
thought to be identical with the base neurine, which Liebreich separated
from nervous tissues, and the two are closely related ; empiiically
choline (C^H^jNOg) is neurine (CjHijISrO), plus water. In constitution
neurine is trimethylvinylammonium hydroxide.

Glyceo'o-jjhosjjhoric acid is glycerin, in which one of the hydroxyl
hydrogens is replaced by phosphoric acid, less hydroxyl ; thus —

HO OH

C3H5HO (H2P03)HO C3H5OH

HO 0— PO3H2

Cglycerin) (phosphoric acid) (glycero-phosphoric acid)

If the other two hydroxyl hydrogens are replaced by the radicle of
stearic acid, we obtain

CH,.0— CVH3,C0
CH.O— Ci,H3,C0
OH
OH



CH2.O— PO



which is distearyl-glycero-phosphoric acid. This is then united to
chohne (less hydroxyl), and we obtain lecithin, or distearyl lecithin, as
it should be more properly termed ; for other lecithins exist in which
palmityl, oleyl, or other fatty acid radicles take the place of stearyl.

The exact manner of the union of the acid with choline is a matter of
controversy, for up to the present lecithin has not been prepared synthetically.
Hundeshagen ^ prepared artificially a choline salt of distearyl-glycero-phosphoric
acid, which is isomeric Avith lecithin, hut which possesses none of its
characteristic properties.

The constitution of lecithin is not therefore that of a salt in which choline
plays a part of the base, as Diaconow - first suggested, but more probably it
is an ether-like combination, the choline radicle being united to the acid by
means of the oxygen of the hydroxyl ; the formula for distearyl-lecithiu
would therefore be (Strecker) ^ —

CH0.O— C1.H05CO

CH,.0— p6-^().CoH,)

OH HO )

The following equation represents the decomposition of lecithin, such
as occurs on boiling it with alkaline solutions : —

C,,H,oNPO,+3H20 = 2Ci,H3cO.,H-C3H9POe+C,Hi,NOo

(lecithin) (stearic acid) (gl3'Cero- (eholiue)

yihosplioric acid)
Lccitli-aRiuriiins. — See p. 69.

Cholesterin. — Oholesterin is contained in small quantities in all jn-oto-
plasmic structures ; it is also found in blood corpuscles and in bile. It is a
large constituent of sebum and similar oily secretions of the skin. In
nervous tissues it is an especially abundant constituent of the white sub-
stance of tlie medullary sbeatli. It may be prepared by making a hot

' Journ. f. 2irakl . C'hcm., Leipzig, 1883, 15d. xxviii. S. 2]0 ; see also E. Oilsou, Zisclir.f,
physiol. Chan., Stiasshurg, Bd. xii. S. 585.

- CcMralhl. f. d. mcd. Wisucnseh., Berlin, 1868.
'^ Ann. d, CJicm., Leipzig, 1868, Bd. cxlviii, S. 77,



CHOLESTERIN.



23



alcoholic extract of the l)rain or spinal cord; on cooling, the cholesterin, to-
gether with protagon and cerebrin, separates out. From this mixture the
cholesterin is dissolved out with ether, and the ether distilled off. To
get rid of traces of lecithin it is heated for an hour with alcoholic potash ;
this decomposes the lecithin, and the residue obtained Ijy evaporating to
dryness is dissolved in a mixture of alcohol and ether ; from this solution,
cholesterin crystallises out as its solvents evaporate off'.

Cholesterin is readily obtained from gall stones Ijy simply extracting
them with boiling alcohol, and treating with alcoholic potash to free it
from extraneous matter.

Like the fats, cholesterin is insoluble in water, but freely solu])le
in hot or cold ether, glycerine, benzol, hot alcohol, and chloro-
form. From anhydrous ether or chloro-
form it separates in the form of needles,
containing no water of crystallisation ;
from alcohol, or ether containing water,

form of rhombic,
contain a mole-
crystallisation, and
by the microscope



it separates in the
bright tables, which
cule of w^ater of
are easily identified

Dry cholesterin melts at 145°, distils %n
vacuo dX 360° 0.; its specific rotatory power
is (a)j, = - 31°'6. It may be recognised by fig. 6.
the following colour tests : —

1. With iodine and concentrated sulphuric acid the crystals give a
play of red, green, and blue.

2. Salkoioshi's reaction} — The cholesterin is dissolved in chloroform
and an equal volume of concentrated sulphuric acid added ; the solution
becomes first red and then purplish, while the sulphuric acid is dark red
with a green fluorescence. On pouring off' the chloroformic solution, it
becomes green and finally yellow.

3. Lichermann-BurcliairVs reaction} — This is a very delicate test, and
is stated to be capable of detecting one part of cholesterin in 20,000 of
solvent. The cholesterin is dissolved in 2 c.c. of chloroform, and ten
drops of acetic anhydride are added, and then concentrated sulphuric
acid drop by drop. The mixture becomes first red, then lilue, and
finally green.

Cholesterin is a monatomic alcohol, the formula of which has been
given as C2gIT430H and Q.r-^^rf)^. The second formula was first
ascribed to the substance by Eeinitzer,^ and it is probably the correct
one, as it has been confirmed by the careful work of Obermliller.* These
observers have prepared a large number of compounds and derivatives
of cholesterin, but its constitution still remains unknown.




Cholesterin crystals. —
After Frey.



The subject is compKcated by the circumstance that there are several
isomeric cholesterins.



^ Arch. f. d. ges. Physiol., Bonn. Bd. vi.

- Liebermann, Ber. d. deutsch. chem. Gcsellsch., Berlin, Bd. xviii. S. 1804 ; Burchard,
" Beitrage zur Kenntniss der Cholesterins," Rostock, 1889.

•* Reinitzer, Monafsh. f. Chem., Wien, 1888, Bd. ix. s. 421.

■• Arch. f. Physiol., Leipzig, 1889; Ztschr. f. phijsiol. Chem., Strassburg, 1889, Bde.
XV. S. 37; xvi. S. 143, 152.



2 4 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

It forms, like glycerine, compounds often called esters, with fatty acids ;
and these compounds, which are found in the fatty secretions of tlae skin,
especially in the fat of sheep's wool (lanoline), are very resistant to bacterial
action ; as a protection to the skin lanoline is therefore admirable.

In lanoline there are two cholesterins at least ; one is levorotatory, the
other (isocholesterin) is dextrorotatory. Isocholesterin was first described
by Schultze,^ and does not give Salkowski's reaction.

Cholesterins of various kinds are present in vegetable tissues.^

The cholesterin of the blood is in combination Avith oleic and palmitic
acids.^

In man the cholesterin of the bile jDasses away in the faeces as koprosterin
(Co-H^gO) ; in the horse as hippokoprosterin (C9-Hr,40 or Co^H^gO) ; in the dog
it is unchanged.*

The Proteids.^

The proteids are the most important substances present in animal
and vegetable organisms ; none of the phenomena of life occur without
their presence ; they are constant decomposition products of, and therefore
probable constituents of, protoplasm.

" They are highly complex and, for the most part, uncrystallisable
compounds of carbon, hydrogen, oxygen, nitrogen, and sulphur,*^ occurring
in a solid, viscous condition, or in solution in nearly all the solids and
liquids of the organism. The different members of the group present
differences in physical, and to a certain extent even in chemical
properties. They all possess, however, certain common chemical reactions,
and are united by a close genetic relationship " (Gamgee).'^

The following table from Gorup-Besanez ^ exhibits the percentage of
proteids contained in the liquids and solids of the body : —



Cerehro-spinal fluid


0-09


Chyle




4-09


Aqueous humour .


0-14


Blood




8-56


Liquor amnii


0-70


Spinal cord .


7-49


Intestinal juice .


0-95


Brain .




8-63


Pericardial fluid .


2-36


Liver .




11-64


Lymph


2-46


Thymus




12-29


Pancreatic juice .


3-33


Muscle




16-18


Synovia


3-91


Tunica m


ediaof arter


les 27-33


Milk . . . .


3-94


Crystalli


ae lens .


38-30



^ Ber. d. dexitsch. chem. GeseUsch., Berlin, Bd. vi. ; Journ. f. prakt. Chem., Leipzig,
N.F., Bd. XXV. S. 458; Ztschr. f. ■phijsiol. Chem., Strassburg, Bd. xiv. S. 522. (Jn
isocholesterin in vernix caseosa see Rappel, ibid., Bd. xxi. S. 122.

- Beneke, JaJiresb. ii. d. Leistung d. ges. Med., Berlin, 1862 ; Hesse, Ann. d.

Chem., Leipzig, Bd. cxcii. S. 177; Bd. ccx., S. 283; Rcinke and Rodewald, ibid., Bd.
ccvii. S. 232; Schnlze and Barbieri, Journ. f. prald. Chem., Leipzig, N.F., Bd. xxv. S.
159, 458 ; Heckel and Sehlagdenliauffen, Com-pt. rend. Acad. d. sc, Paris, 1886, tome cii.
p. 1317 ; Arnaud, ibid., p. 1319. See also Jacobson's paper on " Vegetable Oils," Ztschr.
f. physiol. Chem., Strassburg, Bd. xiii. S. 32.

'■> K. Hiirtlile, Ztschr./. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 331.

* St. Bondzynski and V. Huninicki, Ztschr. f. physiol. Chem., Strassburg, 1896, Bd.
xxii. S. 396.

^ In the preparation of tliis section I have derived special assistance from the articles
''Eiweisskiii-per," in Beilstein's " Handbuch der org. Chemie," and in Ladenlnirg's
" Handwiirterbuch d. Chemie," 1885, Bd. iii. S. 534 (article by E. Drcchsel) ; and from
an article by T. (1. Brodie in ,S'cience Progress, London, 1895, vol. iv. p. 62.

" In some cases ydiosjthorus also is present.

'' "Physiological Chemistry," London, vol. i. p. 4.

8 "Lehrbuch," S. 128.



COMPOSITION OF THE PROTEIDS. 25

The proteid constituents of the animal l^ody are derived from
vegetables either directly, or indirectly through the Ixjdy of another
animal. Synthetic processes do occur in the animal Ijody/ but to a
much greater extent in vegetaljles ; here the proteids are built up from
simpler compounds, derived ultimately from the soil and atmosphere.
In animals, the proteids are converted during digestion into hydrated
products, called peptones ; these are re-converted into proteids,
similar, in a general sense, to those originally ingested, and these are
assimilated to become part of the living organism. In time, they
become subjected to katabolic processes, and give rise to carbonic acid,



Online LibraryE. A. (Edward Albert) Sharpey-SchäferText-book of physiology; (Volume v.1) → online text (page 4 of 147)