Christian Archibald Herter.

Lectures on chemical pathology in its relation to practical medicine, delivered at the University and Bellevue Medical School, New York City online

. (page 11 of 47)
Online LibraryChristian Archibald HerterLectures on chemical pathology in its relation to practical medicine, delivered at the University and Bellevue Medical School, New York City → online text (page 11 of 47)
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backs to the process, especially in the case of children. The
casein is rendered less digestible through boiling owing to
some chemical change which is not fully understood, and
the milk sugar is to some extent converted into caramel.
Moreover the prolonged use of sterilised milk appears in
some instances to have led to the development of scurvy.
These are serious objections to sterilisation by boiling. The
Pasteurisation already referred to is distinctly preferable.
It is possible that even the temperature 167° Fahr. induces
changes in the casein, but as far as we know at present they
are practically unobjectionable. Exposure for ten minutes
to this temperature suffices to kill most pathogenic organisms,
and yet does not impart a boiled taste to milk. If the
Pasteurised milk be rapidly cooled below 50° Fahr. it will
remain sweet for about thirty-six hours longer at ordinary
temperature than milk not Pasteurised, but from which



92 CHEMICAL PATHOLOGY

germs have been excluded by ordinary precautions. Where
one wishes to preserve milk for long journeys it is neces-
sary to kill the spores, and for this purpose boiling is
essential. -

The efforts which have been made to preserve milk by the
addition of salicylates, borates, formalin, or other antiseptics
have not met with favour. Nevertheless I think the use of
milk so preserved much less objectionable than milk very
rich in micro-organisms. Dr. Park tells me that one part of
formic aldehyde (formalin) to 50,000 parts of milk prevents
the multiplication of bacteria. Now there is no reason to
think that formic aldehyde, which is readily oxidised by the
organism to formic acid, can act as a gastro-intestinal irritant
in this dilution. After absorption in such amounts as would
be taken in it can do no haym, since the formic acid into
which it is oxidised is as readily burned by the cells as alcohol. -
It seems to me that milk preserved by formalin could advan-
tageously be used in summer, especially by the poor.

It is important for you to know that bacteria sometimes
i;aduoe chemical changes in milk which lead to severe
symptoms of poisoning, such as repeated vomiting, diarrhoea,
headache, great prostration, and fever. The victims of such
poisoning, which may be epidemic, usually correspond to one
particular milk supply. We know nothing of the chemical
. nature of the bacterial poisons concerned with such disturb-
ances as those to which I refer, but some persons appear to
derive satisfaction from referring to them by the euphonious
name of ' galaoto-toxins.' Milk which contains bacterial
poisons capable of creating serious digestive disorders may
be coagulated, and may not taste like good milk, but gene-
rally it is impossible to judge of its toxic nature from its
appearance or taste. On the other hand, milk may be
coagulated by the commonly present lactic acid organisms
without being injurious.

You will often be asked by your patients with digestive
derangements whether it is proper for them to eat cheese.
The answer to this question depends in a considerable degree
upon the kind of cheese that is wanted. Many patients
with chronic disorders of gastric and enteric origin can
take a small amount of freshly made pot-cheese without any
deleterious results. As a rule the use of old cheese is in-
advisable in chronic dyspepsias. There is, however, some
choice as to such cheeses. A recent investigation of the



THE PEOTEIDS 93

subject by Dr. Vaughan, of Michigan University, shows that
most forms of cheese contain an indol-producing bacillus of
the colon class. This organism was toxic to small animals.
Only four cheeses out of a considerable number did , not
contain this organism. They were Boquefort, genuine
Swiss, and genuine French cheese and sap sago. It is not
clear whether this organism is distinctly deleterious when
cheese is eaten by healthy people, but it is certainly best
not to advise the use of cheeses which contain indol-pro-
duoing organisms for persons who are dyspeptic. Most
cheeses also contain a peptonising germ which improves
the digestibility of the casein. In all acute and subacute
gastro-enterio states it is best wholly to avoid the use of
cheese.

I have already mentioned to you some of the uses of
skimmed milk. You will find comparatively few adults
who are unable to take a fair amount of milk from which
the fat has been largely removed. Buttermilk is frequently
useful as a preparation from which the fat has been very largely
removed. It has the advantage that the churning process
and the moderate lactic fermentation have caused the forma-
tion of small flocculi of casein which are readily digested.
The lactic acid present is unobjectionable, but some persons
greatly dislike its taste. Matzoon and kumyss, or, more
properly, kephyr, are favourite forms of fermented milk.
Kumyss is fermented mare's milk. Kephyr is a modern
substitute for kumyss, prepared by fermenting cow's milk
with kephyr grains. These resemble little bits of cauliflower,
and owe their fermentative action mainly to the saccharo-
myces mycoderma, though they contain also lactic acid-
forming organisms. The fermentation is thus a double one.
The lactic acid organisms change a pare of the sugar into
lactic acid. The vinous ferment decomposes a part of the
sugar into alcohol and carbon dioxide, while destroying a
very small part of the proteid of the miljk. The fermentative
process is permitted to go on to a point where there is a pro-
duction of from 0'6 per cent, to 2 per cent, of alcohol.

In making kephyr from cow's milk it is necessary to
approximate the composition of mare's milk by diluting the
cow's milk and adding a certain proportion of sugar.

It is important to bear in mind the changes undergone
ty the sugar and the casein in the preparation of kumyss
or kephyr. The sugar is very largely replaced by lactic acid.



94 CHEMICAL. PATHOLOGY

alcohol, and carbon dioxide. The casein is precipitated in
the presence of lactic acid, as in the ordinary process of
souring, in the form of flocculi, which are broken up into a
state of fine division by the agitation to which the fermenting
fluid is subjected. The casein is thus in a state which fits it
for rapid digestion and absorption. The carbon dioxide and
alcohol stimulate the secretion of the gastric juice, which is
only slightly excited by the presence of ordinary milk. In
the case of some patients it is desirable to let a portion of the
carbon dioxide escape before the kumyss is drunk.

Matzoon is prepared by a process somewhat similar to
that employed in making kumyss. The ferment which is
added consists of some form of yeast and of several different
lactic acid-producing bacilli. The milk is first boiled to
insure sterilisation, and, after addition of the micro-organic
ferments, the fermentation is carried on at about 105° Eahr.,
a part of the time in an open vessel. The fermentative
process is checked by reducing the temperature. A slow
fermentation continues after bottling, and the older matzoon
contains more lactic acid and somewhat more alcohol and
carbon dioxide than that which is freshly made. The
quantity of alcohol and of carbonic acid is very much less
than in kumyss. The consistence of matzoon is thick and
cream-hke.

Both kumyss and matzoon are useful as foods in the
treatment of acute and chronic digestive disorders. They
are often retained and digested where ordinary milk is
vomited. One great advantage of both these preparations
is the fact that the casein has been precipitated and broken
up into small masses, so that large coagula are not formed in
the stomach. The indications for the use of these forms of
fermented milk are much the same, but matzoon is often
preferable to kumyss owing to its comparative freedom from
carbon dioxide. The thick consistence of matzoon renders
it desirable in many instances to dilute it somewhat. Mat-
zoon is considerably richer in fat than is kumyss, and this
may be a feature of some importance where the use of fat is
desired or has to be shunned. There are many instances
where you will have to leave to your patient the choice
between these two varieties of fermented milk, since in-
dividual taste and tolerance differ so much in regard to
them.

Condensed milk, made by heating fresh cow's milk to the



THE PEOTEIDS 95

boiling-point for the purpose of destroying bacteria and then
evaporating in vacuo at a low temperature, is a preparation
much employed, especially among the poor, in the feeding of
infants. The preservation of condensed milk is accomplished
by adding about six ounces of cane sugar to the pint. Eresh
condensed milk, however, can be obtained to which no sugar
has been added. As a rule the milk is considerably diluted
for use. While exceedingly useful as a temporary food
condensed milk is highly objectionable for the prolonged
feeding of children. The objections are that it contains too
little casein and too little fat, food constituents essential to
the normal development of infants. As a matter of fact you
will see among dispensary children fed on condensed milk a
considerable proportion who have signs of rickets. The
advantages of condensed milk as a temporary food are that
it has been steriUsed, that the casein in the considerable
dilution in which the milk is employed is present in such
small quantities that even infants with feeble digestion can
take it, and that it contains an abundance of sugar, which is
the easiest food for an infant to digest and absorb. Children
fed largely on condensed mUk often grow large and flabby
from the use of so much sugar.

A German prepaai^tion of casein known as caseon or
plasmon has recently been introduced in this country. It
is prepared by precipitation of the casein from fresh milk.
The casein is then dissolved in sodium bicarbonate in the
presence of free carbon dioxide, which prevents the decom-
position .of the casein by the alkali. The casein thus
prepared is dried to a yellowish- white powder almost without
taste and without odour. It is partly soluble in water, and
in part imbibes water and swells. Caseon contains nearly
2 per cent, of fat and about 2^ per cent, of milk-sugar. A
valuable feature is the large content of salts, which amounts
nearly to 7 per cent. Caseon has been found useful as a sub-
stitute for milk where a considerable quantity of fluid is
undesirable. The statement is made that caseon neutralises
more than three times as much acid as an equal weight of
beef, and hence is especially useful in treating hyperchlor-
hydria. It has not yet been extensively tried in this country,
but promises to be a convenient form of proteid food.

Whey, which is prepared by coagulating milk by means
of rennet and straining off the fluid which separates, is par-
ticularly useful for young infants with acute digestive



96 CHEMICAL PATHOLOGY

derangements. It contains a considerable percentage of
milk-sugar, but is low in salts, and of course very low in
proteids and fat. It is often retained in the stomach when
almost everything else is rejected. It should be given
frequently in small amount. Whey is rendered more
palatable by the addition of a little brandy or sherry. It is
best to give it cold.

It may seem to you that I have devoted a dispropor-
tionate amount of time to the discussion of the preparations
of milk, but I do not think this is really the case. Milk
forms so importajit a part of the dietary of invalids that you
should be familiar at least with the more important ways in
which, the different constituents of milk can be utilised in
practice.

There are two other forms in which proteid food is very
much used, and about which I must say a word. These
foods are eggs and the muscles of mammals and birds. The
two parts of fowl's egg, the yolk and the white, are very
different in their chemical nature. The white consists almost
wholly of ' egg albumin,' which is not a single substance, but
a mixture of proteids. This proteid material is easily and
rapidly digested in the raw or slightly cooked condition, but
when firraly coagulated may be only slowly acted on by. the
digestive juices. The egg-yolk contains, in addition to a
small amount of albumen, a large quantity of fat, much
lecethin, probably an ethereal compound of choUn with
glycero-phosphoric acid combined as glyceride with stearic
and palmitic acids, and certain colouring matters. Owing
to the presence of the fat and lecithin the yolk is more apt
to cause digestive derangements than the white. I shall
have occasion later to show you that lecithin under some
circumstances breaks up in the intestine into two basic
nitrogen-containing bodies known as neurin and cholin.
"When present in considerable amount these bodies seem
capable of giving rise to serious toxic symptoms.

I have found it inadvisable to make use of the yolks of
eggs, except with some caution, in persons strongly inclined
to constipation. The whites of the egg can, however, be safely
.employed under these circumstances. Many people will
tell yoii that they are made ' bilious ' by eating eggs. They
usually mean by this that the use of eggs is followed by
headache and some degree of lethargy. I am inclined to
ihink that these symptoms, which undoubtedly arise in



THE PBOTEIDS 97

certain persons, are connected with the imperfect digestion
and excessive putrefaction of proteids belonging to the egg-
yolk. _ These symptoms are especially apt to come on where
there is an inclination to constipation. In some persons one
^g sufBces to bring them on, in others they appear only
when two or more have been eaten. In a child of four years
a single egg-yolk regularly sufficed to bring on a shaip rise
in temperature. Here there was an habitual condition of
excessive intestinal putrefaction. I do not know how to
explain this idiosyncrasy.

I have found it useful in persons who have difficulty in
digesting eggs to prescribe the whites of three eggs with the
yolk of one. By doing this you can often avail yourself of
the valuable nutritive properties of eggs without the risk of
disturbing digestion. The free use of eggs is often helpful
in the treatment of carbohydrate fermentation, as there is
nothing in the egg that affords suitable material for such
fermentation. The caloric value of an egg is fairly high in
proportion to its bulk. It is about seventy large calories.
Two eggs yield about as much caloric energy as one tumbler
of ordinary milk.

The proteids of meat are present as albumin, myo-
globulin, myosin, &c. Besides its proteid elements meat
contains a fair quantity of fats and salts, especially phos-
phates. Extractive materials, that is to say nitrogenous
substances soluble in alcohol, are present in considerable
amount. The extractives in meat like beef, lamb, &c.,
amount to about 0"2 per cent. The presence of these ex-
tractives acts as an agreeable stimulus to the appetite. They
are hence much used in the preparation of soups. The in-
fluence of the extractives upon nutrition has been consider-
ably discussed, but we have very little definite knowledge
on the subject. It is customary among physicians greatly
to restrict the use of meats in cases of nephritis. This
limitation is sometimes carried so far as to exclude red
meats altogether from the dietary of the patient. The
reason given for this exclusion is that the extractives act
injuriously on the kidney. I am inclined to think that this
effect has been greatly exaggerated, and am disposed to
allow my patients with nephritis to eat a certain amount of
red meat, especially where there is an inclination to lose
strength when meat is excluded. I think it much better to
throw a slight additional burden on the kidneys than to run

H



■98 CHEMICAL PATHOLOGY

a serious risk of weakening the general powers of a patient
with chronic kidney disease. It seems to me likely that the
greatest advantage which milk has over meat as a proteid
food, both in digestive derangements and in renal disease, is
its slighter yield of putrefactive products. I consider this
more important than the difference in the quantity of ex-
tractives. It may interest you to know that I have in my
laboratory a dog of medium size which for more than six
months has taken, in addition to meat,' from 20 to 40
grams of Liebig's extract of beef daily. The animal
appears in the best of spirits, and is very active when re-
leased from the cage. He has not a trace of albumin in the
urine, although he has been excreting very large quantities
of extractives for so long a period.

Another reason why milk is to be .given the preference
to meat in cases of chronic disease of the kidney and of the
liver is the relatively slight yield of ammonia that accorn-
panies the absorption of the albumoses and peptones derived
from casein, I told you a short time ago that ammonia
is formed in small amounts in the human intestine as an
end-product of the tryptic digestion of proteids. I algo
. mentioned that in addition to the ammonia arising in this
way within the lumen of the intestine a considerable amount
of ammonia is spUt off from the proteid molecule during
digestion in the wall of the intestine, very hkely.by the
action of lymphoid cells upon proteids passing through the
wall of the gut. Now it has been shown by the experiments
of Selaskin that the quantity of ammonia arising in this way
is much greater in the case of a meat diet than in the case
of a milk diet. The chnical importance of this fact will
.occur to you on considering what becomes of the ammonia
arising in the manner just described. The anunonia split
off in the intestinal waU passes by way of the mesenteric
and portal veins to the liver. In the liver this ammonia
undergoes the same fate as the ammonia which comes from
the cells generally, that is, it becomes converted into urea.
On a meat diet the blood of the portal vein contains a high
percentage of ammonia, and hence yields considerable urea
in the course of twenty-four hours. This urea, which ap-
parently does not represent the nitrogenous waste of cells,
must therefore be regarded as imposing an unnecessary
tax on the kidney as well as on the hver. On a milk diet,
owing to reasons but little understood, but doubtless con-



THE PEOTEIDS 99

neoted with the chemical constitution of casein, this
alimentary urea is small in amount, and has no influence in
overburdening the cells which perform the synthesis of urea
and take part in its excretion.

It is a matter of practical observation that people often
grow nervous and irritable on a dietary containing too liberal
an allowance of meat. These persons may be greatly
benefited by considerably reducing this allowance. It is
customary to allow patients to eat the meat of chicken and
other white meats in cases where red meat is interdicted on
account of its extractives. This is a little surprising in view
of the fact that white meat of chicken actually contains as
much or more extractive material than beef. There is often
something to be said, however, in favour of white meats on
the score of their greater digestibility, perhaps owing chiefly
to a smaller quantity of connective tissue. Let me remind
you of the relatively large nuclein content of the meats of
young animals. Owing to the effect on uric acid excretion
it is undesirable to use meats of this class, such as veal,
where patients are excreting an excess of uric acid. For
the same reason the various sweetbreads must be excluded,
especially the ' heart bread,' or thymus.

The various beef extracts now on the market resemble
one another in being made up largely of extractive materials.
They differ a good deal, however, in the amount of soluble
albumins which they contain. They also differ a good deal
in respect to salts. For details as to these matters I refer
you to books on dietetics. The point which I wish to make
here is that aU these beef extracts have a certain utihty
which they owe to the stimulation and refreshing effects of
the extractives. Some of them, however, have no other
virtue than this and are not to be regarded as foods, since
they pass through the body without yielding energy to it
through their metabolic decomposition. One of the best
preparations is that known as Mosquera's beef meal. It is
not only palatable, but. contains a considerable amount of
soluble proteids which give it a value as a food.

The preparation called somatose has recently come into
prominence as a food. Somatose is a mixture of albumoses
obtained from the action of a ferment on meat proteids. It
is therefore a predigested food. There are conditions in
which somatose is useful on account of the readiness with
which it is absorbed. The indications for its use are much

B 2



100 CHEMICAL PATHOLOGY

the same as for peptonised milk, but it has the advantage
over peptonised milk of not necessitating the use of
much fluid. While this concentration is certainly ad-
vantageous at times, it also has its drawbacks, the chief
one being that it is very liable to set up excessive peristalsis
and more or less pain. When cautiously employed in
conjunction with other food-stuffs it is sometimes distinctly
helpful for short periods of time on account of its ready
absorption. ,

The last kind of food to which I shall refer to-day is
gelatin, a substance of peculiar interest to the physiologist,
for the reason that while closely resembling the proteids in
many chemical characters it differs from them in the highly
important respect that it is incapable of replacing proteid
waste by building up cell material. The resemblance to
proteids relates to elementary composition, to the conversion
into peptones by digestion, to metabolic decomposition and
oxidation into urea, carbon dioxide, and water, and to the
yield of leucin (a-amido-iso-butyl-acetic acid) and glycocoU
(amido-acetic acid) under suitable conditions. Gelatin gives
the biuret reaction, but as it contains no tyrosin radical it
does not react with Millon's reagent.

Notwithstanding gelatin contains nitrogen it must be re-
garded as a non-proteid foo(J, because it cannot replace the
proteids of the diet except to a limited extent. Like the
carbohydrates and fats, it saves proteid waste, and it is
possible to remove from the diet a certain amount of proteid
if this be replaced by gelatin to an amount equal to about
twice the caloric value of the gelatin. According to one
estimate one-fifth of the ordinary quantity of proteid may be
so replaced ; according to another the quantity is consider-
ably larger than this. It seems clear that gelatin is really
more ef&cient as a saver of proteid than either carbohydrates
or fats, and I am incUned to believe that we might make
more extended use of gelatin as an element of the dietary
of patients who show proteid waste. A practical advantage
of gelatine is its ready digestibility and absorption, but it
must be remembered that patients soon tire of its use in con-
siderable amounts.

Gelatin is obtained by boihng collagen with water. The
process involves the appropriation of water, is in fact an
hydration process. The collagen which yields gelatin is an
important constituent of connective tissues and the ossein of



THE PBOTEIDS 101

bones. One might perhaps suppose that this collagen can
be replaced by gelatin, but there is some experimental
evidence that this is not the case, and that collagen is made
only from proteid food. Gelatin introduced into the circula-
tion is not assimilated, but reappears in the urine. It has,
however, the property of increasing somewhat the coagula-
bility of the blood, and efforts have been made to utilise
this fact in the treatment of aneurysms where it is the desire
to favour local clotting — with what success I am unable to
say. It is also stated that the hsematuria of haemophilia
has been checked by free use of gelatin as a food.

I have mentioned that the decomposition of gelatin
yields no tyrosin. Might we not make use of this peculiarity
of gelatin where we wish to limit putrefactive cleavages in
the intestine with the production of aromatic substances ?
It is from the tyrosin of the proteid molecule that we get
phenol, and probably indol and other products of the
aromatic class. These are the bodies which give us the
ethereal sulphates of the urine, and it is conceivable that
these substances might be considerahly reduced if a portion
of the proteid of the food, say one-fifth or one-quarter, could
be replaced by means of gelatin. This is, however, only a
suggestion for the practical workings of which I would not
vouch.



Online LibraryChristian Archibald HerterLectures on chemical pathology in its relation to practical medicine, delivered at the University and Bellevue Medical School, New York City → online text (page 11 of 47)