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

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

. (page 19 of 147)
Online LibraryE. A. (Edward Albert) Sharpey-SchäferText-book of physiology; (Volume v.1) → online text (page 19 of 147)
Font size
QR-code for this ebook


The milk of other animals. — Some of the principal analyses are
collected into the f oUowins; table : —

















Eeference


Animal.


Water.


Caseinogen.


Albumin.


Fat.


Lactose.


Salts.


to Notes
below.


Dog .


75-4


9-91


9-57


3-19


0-73


8


Cat .


81-6


9-08


3-33


4-91


0-58


8


Goat .


86-91


3-69


4-09


4-45


0-86


9


Goat .


86-75


3-64


5-35


3-60


0-66


10


Sheep


83-5


5-74


6-14


3-96


0-66


11


Sheep


82-84


4-7


4-8


3-4-6


0-6


12



^ Journ. de 2}harm. et chim.. Paris, tome xxx, p. 464.

- Ann. d. Cheni., Leipzig, Bd. xcvii. S. 150. ^ Loc. cit.

^ Landio. Versuchs. Stat., Beriin, Bd. xii. S. 405. ^ Loc. cit.

« Ztschr.f. rat. Med., Bd. x. S. 285.

' Arch. f. d. ges. Physiol., Bonn, Bd. ii. S. 166.

® Taken from Konig's analyses. The milk is acid, rich in proteids and calcium. The
lactose is increased hy starchy, and lessened though not abolished by a flesh diet (Bensch,
Ann. d. Chem., Leijizig, Bd. Ixi. S. 221 ; Poggiale, Gaz. med. de Paris, Ser. 3,
tome X. p. 259). See also Simon, "Die Frauenniilch," Beriin, 1838; Dumas, Oompt.
rend. Acad. d. sc, Paris, tome xxi. p. 707 ; Keminerich, CentralM. f. d. med. JVissensch.,
Beriin, 1866, No. 30 ; Szul)otin, ibid.. No. 22.

'■' Taken from Konig.

^^ From Pizzi's analyses {Staz. fife,r. Agrar., 1894, Bd. xxvi. S. 615 ; Abstract in Journ.
Chem. Soc, London, 1896, vol. ii. p. 120). Goats' milk differs from cows' milk in smell
and taste, and in containing more insoluble volatile fatty acids. In reindeer's milk these
acids are less abundant (Solberg, Oentralhl. f. agric. Chem., Leipzig, 1896, S. 15).

^^ From Konig.

^^ From Vernois and Becquerel, Union viid., Paris, 1867, p. 78.



THE MILK OF OTHER ANIMALS.
The milk of other animals— conti7iued.

















Reference


Animal.


Water.


Caseinogen.


Albumin.


Fat.


Lactose.


Salts.


to Notes
below.


Sheei^


80-42


4-44


9-66


4-4


1-1


1


Mare


90-06


1-89


1-09


6-65


0-31


2




90


1-S 0-3


1-3


5-5


0-3


3




92-5


1-3 0-3


0-6


4-7


0-3


4




91-0


1-05


1-3


5-7


0-3


5


Ass .


90-0


2-1


1-3


6-3


0-3


6


Ass




90-5


1-7


1-4


6-40


7


Ass




89-0


3-5


1-8


5-0


0-5


8


Pig




82-37


6-09


6-4


4-04


1-06


9


Pi^




83-0


7-0


7-0


2.0


1-05


10


Pig




81-8


5-3


6-0


6-0


0-08


10


Mule




89-3


2-6


1-9


6-03


0-53


11


Hippopotamus .


90-0




4-5




0-1


12


Camel


86-3


3-7


2-9


5-8


0-6


13


Elephant .


67-85


3-09


1-95


8-84


0-65


14


Dolphin


48-67




43-76




0-46


15


Buftalo .


82-20


4-13


7-95


4-75


0-97


16


Rabbit


69-50


15-54


10-4


1-95


2-56


17



Salts of dogs and mares' milk. — These may be compared in the
following table of Bmige's ^^ with those we have already studied : —





HraiAK.


Dog.


Cow.


Mare.




I.


n.


I.


II.


K„0


0-78


0-71


1-41


1-68


1-76


1-04


Na„0










0-23


0-26


0-80


0-69


1-11


0-14


CaO










0-33


0-34


4-53


4-28


1-59


1-23


MgO










0-06


0-06


0-19


0-21


0-21


0-12


FeoOg










0-003


0-006


0-02


0-01


0-003


0-015


P.O.










0-47


0-47


4-93


4-67


1-97


1-31


CI .










0-43


0-44


1-62


1-8


1-69


0-31


Total ash per 1000








2-22


2-18


13-15


12-96


7-97


4-17



1 From Pizzi. Sheep's milk contains a high percentage of fat.

- From Konig.

^ From Biel, Jahresb. u. d. Fortschr. d. Thier-Ghem., Wiesbaden, 1864, S. 171.

4 From Soxhlet, ihid., 1878, S. 152.

^ From Weiske and Schrodt, ibid., 1878, S. 151. The caseinogen of mares' milk is more
like that of human than of cows' milk. This is the milk originally used in the prex^aration
of koumiss and similar fermented liquors in Russia.

® From Konig.

^ From Gubler and Quevenne, Gmelin's "Handbuch," Bd. viii. S. 267.

* From Vernois and Becqiierel. Asses' milk is much used by invalids.

^ From Konig.

■'*' From Leutuer, in Gorup-Besanez, "Lehrbuch," S. 424.

^^ From Aubert and Colby, Chem. News, London, vol. Ixviii. p. 168.

12 From Ckem. Centr.-BL, Leipzig, 1871, S. 149.

1^ From Dragendorf, Hid., 1867, S. 78. See also Vernois and Becquerel for analyses of
camels' milk.

■'"* From Konig.

■'•' From Frankland, Chem. News, London, 1890, vol. Ixi. Note the enormous percentage
of fat.

1'' From Pizzi. For buffaloes' milk, see also Pappel and Richmond, Journ. Chem, Soc,
London, 1894, p. 754.

" From Pizzi.

i^Diss., Dorpat., 1874 ; Ztschr. f. jjhysiol. Chem., Strassburg, Bd. xiii. S. 399.



132 THE CHEMISTRY OF THE TISSUES AND ORGANS.

The chief acid present throughout is phosphoric acid ; the chief base
in hiunan milk is potash ; but tliis in most other mammals is second to
lime ; in dogs' milk the hme is especially high.

In connection with the iron in the milk it is to be noticed, that
although the other mineral constituents of the milk are present in the
proportion in which they are contained in the foetal tissues, the quantity
of ii'on in milk is less.



One hundred parts by


weight of


ash contain —






In New-born Dog.


In Dogs' Milk


K2O




11-42


14-98


K'a20






10-64


8-80


CaO






29-52


27-24


MgO






1-82


1-54


Fe^Og






0-72


0-12


P2O5






39-42


34-22


Ci .






8-35 . •


16-90



The shghtly different proportion in soda and potash is easily ex-
plained by the fact that in the young animal the potash-rich muscle is
increasing, and the soda-rich cartilage is diminishing. The high per-
centage of chlorine in the milk is also explicable, on the hypothesis that
the chlorides serve not only to build up tissues, but also largely as
solvents in removing waste products. But the percentage of iron
in the milk is only one-sixth of that in the foetal tissues. The foetus
obtains its supply of iron before birth through the placenta, and stores
it in the hver (see p. 86). As the young animal grows, a kilogram of
body weight contains less and less iron.

Iron appears to pass to the offspring through the placenta rather
than by the milk, because of the difficulties of absorbing iron by the
alimentary canal, and the danger that htematogenous {i.e. nuclein)
compounds may there become the prey of bacteria. Bunge further
regards it as probable that the large amount of iron which passes to the
foetus is not all derived from tlie mother's food during the relatively
short period of pregnancy, but that a storage of iron occurs in the
maternal organs even before the first conception ; and this may explain
the occurrence of chlorosis at the age of puberty.

The carbohydrates of milk. — The most important carljohydrate
in milk is lactose, or milk-sugar, the properties of which are described
on page 12. It is found in varying quantities in the milk of all
animals ; the only exception to this rule liitherto noted is that of
the Egyptian buffalo {Bos huhalus), where it is replaced by another
sugar christened tetvjikose^ by Pappel and Eichmond;^ it }uelds dex-
trose only on hydrolysis.

Though lactose is not fermented by yeast, yet it undergoes the
alcoliolic fermentation under the influence of other schizomycetes, as
in the preparation of koumiss and kephir.

Kittliausen ^ found in milk another carbohydrate which is soluble in water,
and is not crystallisable ; its reducing power is low, and increased after boiling



^ After the Khedive of Egypt.

- Journ. Chem. Soc, London, 1894, p. 754.

^ Journ. f. in-akt. Chem., Leipzig, N. F., Bd. xv.



THE FATS OF MILK. 133

with acid. Landwehr ^ identified it as animal gum, Bechamp - as dextrin.
J. Herz''^ found granules in milk, which behave towards iodine like starch;
he called them "animal amyloid."

The fats of milk. — Milk fat has a specific gravity of from 949
to 996.'^ It consists of pahnitin, stearin, and olein, with small quantities
of triglycerides of l^utyric, caproic, caprylic, capric, myi'istic, and arachic
acids in addition.^ It also contains small quantities of lecithin, choles-
terin, and a yellow lipochrome.

The amount of fat in cream varies from 14 to 44 per cent. In butter,
besides fat, there are small quantities of caseinogen and lactose. The
fats of cows' butter consist of 68 per cent, of pahnitin and stearin, 30
per cent, of olein, and 2 per cent, of the specific butter fats.^ Their
melting point is 31^ to 34" C. The volatile fatty acids in cows' milk, accord-
ing to Duclaux,'^ amount to 7 jDer cent., of which 3-7 to SI is butyric, and
2'0 to 3'3 is caproic acid. Some analysts give still higher percentages.

By exposure to the air butter becomes rancid ; this is partly due to
the production of lower fatty acids from the higher fats (see p. 19),
partly to the formation of acrolein from glycerine, and partly, and
according to Hagemann chiefly, to the formation of lactic acid from the
entangled lactose.

The composition of butter is very variable. Thus, in Finland butter,
Koefoed^ found two fatty acids of the acrylic series in addition to oleic
acid; 100 parts of the fatty acid contained 66 of these acids, 28 of
palmitic, 22 of myristic, 8 of lauric, 1"5 of butyric, 2 of caproic, 2 of capric,
and 0"5 of caprylic acid. According to Wanklyn,^ there is no true palmitic
acid in butter ; the acid is aldepalmitic acid (C^gH3Q0.2).

The, fats of human milk are somewhat different from those of cows'
milk. They have been the subject of two recent researches — one by
Euppel,^*^ the other by Laves.^^

Their melting point is 34° C, and solidifying point 20°-2 C. Their
specific gravity at 15° C. is 966. The fatty acids found are butyric,
caproic, capric, myristic, palmitic, stearic, and oleic acids, all combined
with glycerine. The presence of formic acid ^^ is also inferred from its
reducing action, but not by any further tests. Human milk is poor in
volatile acids (Euppel).

Laves confirms this work, and gives some quantitative results. The
fat contains 1'4 per cent, of volatile acids, 1'9 of acids soluble in water,
and 49-4 (a very high percentage) of unsaturated acids. The volatile

1 Arch. f. d. ges. Physiol., Bonn, Bde. xxxix. and xl.

^ Bull. Soc. chim., Paris, Ser. 3, tome vi.

3 Chem. Ztcj., Cothen, Bd. xvi. S. 1594.

•* Bohr, Jahresh. i'l. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. x. S. 182.

^ Grunzweig, Ann. d. Chem., Leipzig, Bd. clxii. S. 215; E. Wein, Diss., Erlangeu,
1876; Chevreul, " Recherches sur le corps gras," Paris, 1823; Lerch, Ann. d. Chem.,
Leipzig, Bd. xlix. S. 212 ; Heintz, ihid., Bd. Ixxxviii. S. 300.

« Bromeis, ibid., 1842, Bd. xlii. S. 46.

"^ Compt. rend. Acad. d. sc, Paris, tome civ.

^ Overs. 0. d. Jc. Danske Vidensk. Selsk. Fork., Kjobenhavn, 1891.

^ Chem. Heivs, London, vol. Ixiii.

10 Ztschr.f. Biol., Mltnchen, Bd. xxxi. S. 1.

'^^ Ztschr. f. ]}hijsiol. Chem., Strassbnrg, Bd. xix. S. 369.

^" Duclaux {loc. cit. ) found formic acid in cows' butter which had been exposed to
sunlight.



134 THE CHEMISTRY OF THE TISSUES AND ORGANS.

acids contain equal quantities of caproic, caprjlic, and capric acids, and
the merest traces of butyric acid. The principal acids present, as is
usual in animal fat, are palmitic, stearic, and oleic acids, and one or
more acids of lower molecular weight, including myristic acid. The
melting point of the mixture of acids is 37° to 39°, and of the fat itself
30° to 31° C.

The proteids of milk. — The proteids which occur in milk are
three in number. The most abundant and most important of these is
caseinogen. It is tliis proteid which is acted upon by rennet, and
converted into casein or cheese.^ The other two proteids are only
present in small quantities ; they are called lactoglobuhn and lact-
albumin. Proteoses and peptone were described in milk by many of
the older workers. This was due to the use of faulty methods of
analysis (see p. 41).^

Coagulation of milk. — When milk is allowed to stand at the
ordinary temperature exposed to the air, the chief change it undergoes
is the lactic acid fermentation. The acid formed precipitates a part of
the caseinogen, but this is a different thing from the conversion of
caseinogen into casein. Sometimes, however, certain aerobic bacterial
growths act like rennet in causing a true curd. Certain of the higher
plants (Ficus, etc.) also curdle milk.

The agency by which the clot is most readily formed is that of
rennet. This is a ferment secreted by the stomach, and is usually obtained
from the stomach of sucking animals, like the calf. The pancreatic
juice also has a curdling action on milk (see p. 137), and extracts of
many tissues (such as testis, liver, lung, muscle) have a feeble action of
the same nature.^

Hammarsten* and, later, Friedberg^ showed conclusively that the
active principle of rennet is not pepsin ; that it requires for its efficient
action the presence of calcium salts, of which the phosphate is the one
which is mostly present in the milk, and that it will act in a weakly
acid, neutral, or alkaline solution. It acts most readily at 40° C, and
is destroyed at 70° C. The ferment itself in the rennet extracts is
termed chjmiosin by Friedberg, and rennin by Foster.^

When rennet is added to cows' milk the result is a coherent clot or
curd, which expresses a clear yellowish fluid, the whey. The curd
contains the fat entangled with the casein ; the whey contains the other
proteids, sugar, and salts of the milk. In human milk the curd is
usually composed of smaller floccuh, and a similar flocculent coagulation
can be produced in cows' milk by previously boiling it, or by diluting it.
Lime water, soda water, or barley water are generally used as diluents
for this purpose.

The coagulation of milk is somewhat analogous to that of blood,
and the analogy is accentuated by the fact that in both cases calcium

^ The utility of this nomenclature is at once apparent when casein and caseinogen are
conti-asted with fibrin and fibrinogen, myosin and myosinogen, even althongh the analogy
is not complete in details. Hammarsten, however, prefers to call the proteid in milk,
casein ; while the coa.gnlated proteid he terms, after Schulze and Rose {Landw.
,Versuchs. Stat., Berlin, Bd. xxxi. ), paracasein.

^ For a critical article on the estimation of the various proteids in milk, see Schlossmann,
Ztschr. f. physiol. Chein., Strassburg, 1896, Bd. xxii. S. 197.

* Edmunds, Journ. Physiol., Camliridge and London. 1S96, vol. xix. p. 465,

■• Jahresb. n. d. Fortsclor. d. Thier-Chcm., Wiesbaden, 1874, S, 135,

'^ Journ. Am. Chem. Soc, N. Y., 18S8, p. 15.

'' "Text- book," 5th edition, p. 519.



THE PR O TEIDS OF MILK. 1 3 5

salts appear necessary, and that coagulation can be delayed or prevented
by decalcifying the fluid. This is most readily done by addmg a small
quantity of a soluble oxalate.^ Peptone has, as with blood, a retarding
effect on coagulation.^

Green ^ has suggested that there is a definite relationship between
the ferment and the calcium salt, resembling that which exists between
pepsin and hydrochloric acid. Hammarsten ^ and, later, Einger ^ showed
what this relationship is. The formation of casein from caseinogen is, in
fact, a double process : the first action is that of the ferment which
converts the caseinogen into what we may call " soluble casein " ; the
second action is that of the calcium salt which precipitates the casein
as curd, which is probably caseate of hme. This may be shown by
taking a solution of caseinogen and adding rennet ; if the mixture is
warmed to 40° C, no visible change occurs ; but nevertheless soluble
casein, and not caseinogen, is now present. If the mixture is now boiled
to destroy the ferment, cooled, and a drop of 2 per cent, calcium chloride
added, the formation of a curd takes place.^

Casein and caseinogen differ in several of their properties. The
curd of caseinogen precipitated by acetic acid is not nearly so coherent
as the curd of casein produced by rennet. The precipitabihty of
caseinogen by acid is not prevented by the addition of an oxalate,
and there is 13 per cent, more calcium phosphate used up in rennet
coagulation than in acid precipitation.'^

The action of remain upon caseinogen is not a simple conversion of
that proteid into one of a more insoluble kind ; but just as the fibrin
ferment sphts the molecule of fibrinogen into an insoluble proteid, fibrin,
and a soluble globuhn which passes into the serum, so rennin sphts
the caseinogen molecule into two parts : one part is the curd or casein ;
the other is a soluble proteid which passes into the whey, and is termed
" whey proteid " by Hammarsten. This is the equivalent of the lacto-
protein of other investigators. Some of these state it is hke a proteose
or peptone. It is certainly not coagulated by heat ; it is precipitable by
saturating with magnesium sulphate ; rennet has no further action on
it. It does not, however, give the pink biuret reaction.^ It contains
C, 50-3 ; and K, 13-2 per cent.''

Caseinogen. — This proteid may be precipitated from milk by the
addition of acids hke acetic, or by saturation with salts Hke sodium
chloride and magnesium sulphate, or by half -saturation with ammonium
sidphate. In all cases the fat of the milk is entangled with the
precipitate. Caseinogen may be most readily prepared free from fat
by first half -saturating the milk with ammonium sulphate ; the precipi-
tate is collected, well washed with half-saturated solution of the same

^ Arthur and Pages, Arch, de phijsiol. norm, et patli., Paris, Ser. 5, tome ii. ; Compt.
rend. Soc. do bioL, Paris, tome xliii. The addition of oxalates does not absolutely decalcify
blood or milk ; the calcium in close combination with the proteid remains unprecipitated.
See Schiifer (Froc. Physiol. Soc, 1895, p. xviii) ; }lamma.vsteii {Ztschr. f. jjhysiol. Chem.,
Strassburg, 1896, Bd. xxii. S. 333), and also the article in this book on Blood.

^ Edmunds, loc. cit. •* Journ. Physiol., Cambridge and London, vol. viii. p. 371.

■* " Zur Kenntniss des Kaseins," Nova Acta Reg. Soc. Sclent., Upsala, 1877. Festschrift.

^ Jottrn. Physiol., Cambridge and London, vol. xi. p. 464.

^ Here the analogy of casein and fibrin breaks down. 1\\ blood coagulation the cal-
cium salts assist in the genesis of the fibrin ferment rather than in the formation of
fibrin from fibrinogen (Hammarsten, loc. cit.)

■^ D. F. Harris, Journ. Anat. and Physiol., London, 1894, vol. xxix. p. 188.

^ Halliburton, Journ. PhydoL, Cambridge and London, vol. xi. p. 462.

® Koster, Jahresb. ii. d. Fortschr. d. Thier-Chem., Bd. xi. S. 14.



136 THE CHEMISTRY OF THE TISSUES AND ORGANS.

salt, and then distilled water is added. This, in virtue of the salt adhering
to the precipitate, dissolves out the caseinogen, and carries it through
the filter, the greater part of the fat being left behind. From this
solution the caseinogen is precipitated by acetic acid ; it is collected,
thoroughly washed, and dissolved in dilute alkali like lime water, and
purified by repeated precipitation with acid and re-solution in alkali.

Einger's method of obtaining caseinogen is a slight modification of
that of Hammarsten : he precipitates caseinogen with acetic acid, collects
and washes the precipitate, and grinds it up in a mortar with calcium
carbonate ; the mixture is thrown into excess of distilled water ; the fat
rises to the top ; the chalk falls to the bottom, and the intermediate
opalescent fluid is a solution of caseinogen. The separation into the
three layers may be hastened by the use of the centrifuge.

In both cases, the caseinogen, if it has been thoroughly washed from
soluble calcium salts, will not clot with rennet ; the lime water in the one
case and the calcium carbonate in the other not being sufficient to
cause the separation of the curd : this, however, occurs immediately on
the addition of a soluble salt of lime like the phosphate or chloride.

Solutions of caseinogen are not coagulated by heat. By prolonged
heating they become opalescent ; this often disappears on cooling. In
some cases a scum forms on the surface, as in milk.

Caseinogen is not a globulin ; still less is it an alkali albumin : it is
a nucleo-albumin.

Analyses by Chittenden^ gave the following result — C, 53'3 ; H, 7"07 ;
N, 15-91; S, 0-82; 0, 22-04. The amount of phos]3horus was not
estimated. Danilewsky ^ considered it to be a mixture of two proteids,
but this, as Hammarsten ^ showed, was due to faulty methods of prepara-
tion. Chittenden made a study of the caseoses and proteoses obtainable
from it by digestion.^ Sebelien,^ who also prepared casein peptone,
states it is optically inactive — a most exceptional occurrence among pro-
teids. The most interesting fact about its digestion by gastric juice,
however, is, that it yields a precipitate of nuclein, or rather of pseudo-
nuclein^ (see pp. 65, ^^').

The amount of and varieties of calcium phosphate in union with
caseinogen and casein has been investigated by Soxhlet and Soldner''
and by Courant.^ Soldner describes two calcium compounds of
caseinogen, containing respectively 1-55 and 2-36 per cent, of CaO ; these
are called dicalcium casein and tricalcium casein. Moraczewski ^ finds
that the yield of pseudo-nuclein varies from 1-3 to 21-1 per cent,
of the caseinogen employed; he finds that the amount of phos-
phorus in the pseudo-nuclein varies from 0-88 to 6-86 per cent. The
whole phosphorus of the casein is not in the nuclein ; the quantity
in the nuclein is given as from 6 to 60 per cent, of the whole. This has
been confirmed by Salkowski and Hahn.^^ These observers also find that

^ Btud. Lah. Physiol. Ghem., New Haven, vol. ii. p. 156 ; iii. p. 66.
" Ztschr. f. physiol. Cliem., Strassbiirg, Bd. vii. S. 433.
■'Ibid., Bd. vii. S. 227.

* On peptonised milk see also Horton-Smith, Journ. Physiol., Cambridge and London,
1891, vol. xii. p. 42.

'' Centralbl. f. agric. Chem., Leipzig, 1889, S. 717.
® Moraczewski, Ztschr. f. 2yhysiol. Chem., Strassburg, Bd. xx.
^ Loc. cit. 8 Loc. cit.

^ Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xx. S. 28.
" Arch.f. d. ges. Physiol., Bonn, Bd.'lix.



THE PR O TEIDS OF MILK. 1 3 7

the pseudo-nuclein is partly soluljle in gastric juice ; Mt is by far the
most sohible of the nucleiiis,^ though the majority are partly soluble
after pancreatic digestion.^

Casein. — This name should be restricted to the proteid formed by
the action of rennin, or of ferments that act like rennin. As a general
rule, it is more insoluble than caseinogen ; it is, however, readily solulde
in dilute alkalis such as lime water. From these solutions it is readily
precipitable by traces of calcium chloride ; and also by sodium chloride
(Harnmarsten). The precipitate with calcium chloride increases on
heating, but, like many calcium compounds, partially redissolves on
cooling (Einger).

The main distinction between casein and caseinogen is, however,
that which was first insisted on by Hammarsten, namely, that caseinogen
can be curdled by rennet, casein cannot. Some recent work by D. F.
Harris "^ and Peters ^ appeared to cast doubt upon this essential distinction,
and to suggest the possibility of recoagulation of casein, analogous to
that of myosin. The fallacies into which these observers were drawn
have been pointed out independently by Edmunds,^ Hammarsten,^ and
E. Benjamin.^ Peters, for instance, used a preparation of rennet, rich in
sodium chloride and calcium salts ; the precipitate he obtained by adding
this to a solution of casein was due to these salts, not to the ferment.

Pancreatic casein. — An interesting variety of casein is that formed
by the action of pancreatic juice on milk, which has been recently
investigated by Brodie and myself.^

Kuhne^*' was the first to point out that extracts made from the
pancreas of the dog cause milk to coagulate ; this action was described
in some detail by Sir William Eoberts.^^ Various conditions which
influence the clotting were observed by Edkins,"'^ and the occurrence of
the action in pancreatic extracts from a number of animals determined by
Harris and Gow.^^

Our attention was drawn to the subject by a sentence in Prof.
Gamgee's " Physiological Chemistry," ^* in which he points out that it does
not necessarily follow that because extracts of the organ have a clotting
action, the pancreatic juice possesses it also.

We accordingly performed experiments with the actual pancreatic



Online LibraryE. A. (Edward Albert) Sharpey-SchäferText-book of physiology; (Volume v.1) → online text (page 19 of 147)