Philip B. (Philip Bovier) Hawk.

Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science online

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Online LibraryPhilip B. (Philip Bovier) HawkPractical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science → online text (page 24 of 70)
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pound ultimately forms as fine acicular crystals which rise to the surface.

If we do not wait for the production of the crystalline body but as soon as the
blue color forms, shake the aqueous solution with chloroform, the blue color dis-
appears from the solution and the chloroform assumes a pinkish-red hue.
This is a distinguishing feature of the indole reaction and facilitates the differen-
tiation of indole from other bodies which yield a similar blue color. A very sat-
isfactory method for the quantitative determination of indole is based upon the
principle underlying this test (see chapter on Feces).

2. Formaldehyde Reaction (Konto). To i c.c. of the material under exami-
nation in a test-tube add 3 drops of a 40 per cent solution of formaldehyde and i
c.c. of concentrated sulphuric acid. Now agitate the mixture and note the appear-
ance of a violet-red color if a trace of indole is present. The test is said to serve
for the detection of indole when present in a dilution of i : 700,000.

Skatole gives a yellow or brown color under the above conditions.

3. Cholera-red Reaction. To a little of the material under examination in a
test-tube add one-tenth its volume of a 0.02 per cent solution of potassium nitrite
and mix thoroughly. Carefully run concentrated sulphuric acid down the side
of the tube so that it forms a layer at the bottom. Note the purple color. Neu-
tralize with potassium hydroxide and observe the production of a bluish-green

4. Nitroprusside Reaction (Legal). To a small amount of the material under
examination in a test-tube add a few drops of a freshly prepared solution of sodium
nitroprusside, Na 2 Fe(CN) 5 NO+ 2H 2 0. Render alkaline with potassium hydroxide
and note the production of a violet color. If the solution is now acidified with
glacial acetic acid the violet is transformed into a blue.


5. Pine Wood Test. Moisten a pine splinter with concentrated hydrochloric
acid and insert it into the material under examination. The .wood assumes a
cherry-red color.

6. Nitroso-indole Nitrate Test. Acidify some of the material under examina-
tion with nitric acid, add a few drops of a potassium nitrite solution and note the
production of a red precipitate of nitroso-indole nitrate. If the residue contains
but little indole simply a red coloration will result. Compare- this result with the
result of the similar test on skatole.

Tests for Skatole

1. Herter's Para-dimethylaminobenzaldehyde Reaction. 1 To 5 c.c. of the
distillate or aqueous solution under examination add i c.c. of an acid solution of
para-dimethylaminobenzaldehyde 2 and heat the mixture to boiling. A purplish-
blue coloration is produced 3 which may be intensified through the addition of a
few drops of concentrated hydrochloric acid. If the solution be cooled under
running water it loses its purplish tinge of color and becomes a definite blue.
The solution at this point may be somewhat opalescent through the separation of
uncombined para-dimethylaminobenzaldehyde. Care should be taken not to
add an excess of hydrochloric acid inasmuch as the end-reaction has a tendency
to fade under the influence of a high acidity.

A rough idea regarding the actual quantity of skatole in a mixture may be
obtained by extracting this blue solution with chloroform and subsequently
comparing this chloroform solution, by means of a colorimeter (Duboscq), with
the maximal reaction, obtained with a skatole solution of known strength.

2. Color Reaction with Hydrochloric Acid. Acidify some of the residue with
concentrated hydrochloric acid. Note the production of a violet color.

3. Acidify some of the residue with nitric acid and add a few drops of a potas-
sium nitrite solution. Note the white turbidity. Compare this result with the
result of the similar test on indole.

Tests for Phenol and Cresole

1. Color Test. Test a little of the solution with Millon's reagent. A red
color results. Compare this test with the similar one under Tyrosine (see page

2. Ferric Chloride Test. Add a few drops of neutral ferric chloride solution
to a little of the material under examination. A dirty bluish-gray color is formed.

3. Formation of Bromine Compounds. Add some bromine water to a little
of the fluid under examination. Note the crystalline precipitate of tribrom-
phenol and tribromcresol. The reaction for phenol is as follows :

Phenol. Tribromphenol.

^Herter: Bacterial Infections of the Digestive Tract, 1907, p. 141.

2 Made by dissolving 5 grams of para-dimethylaminobenzaldehyde in 100 c.c. of 10
per cent sulphuric acid.

3 If the color does not appear add more of the aldehyde solution.


4. Nitric Acid Test. Add some nitric acid to some of the material under
examination. Heat and note a yellow color due to the production of picric acid
(trinitrophenol) from phenol. This is the reaction :

Phenol. Picric acid.

Tests for Oxyacids

1. Color Test. Test a little of the solution with Millon's reagent. A red color

2. Bromine Water Test. Add a few drops of bromine water to some of the
nitrate. A turbidity or precipitate is observed.

Test for Skatole -carbonic Acid

Ferric Chloride Test. Acidify some of the nitrate with hydrochloric acid, add
a few drops of ferric chloride solution, and heat. Compare the end-reaction with
that given by phenol.


THE feces are the residual mass of material remaining in the intes-
tine after the full and complete exercise of the digestive and absorptive
functions and are ultimately expelled from the body through the rectum.

They may be said to be composed of the following substances:

1. Food residues: (a) those portions of the food which have escaped
absorption, and (b) that part of the diet either not digested or incapable
of absorption.

2. The remains of the intestinal and digestive secretions not
destroyed or reabsorbed.

3. Substances excreted into the intestinal tract, notably salts of
calcium, iron, and other metals.

4. The bacterial flora of the intestinal tract.

5. Cellular elements to which may be added, under pathological
conditions, blood, pus, mucus, serum, and parasites.

6. Abnormally: enteroliths, gall stones, and pancreatic calculi.
The amount of the fecal discharge varies with the individual and the

diet. Upon an ordinary mixed diet various authorities claim that the
daily excretion by an adult male will aggregate 110-170 grams with a
solid content ranging between 25 and 45 grams; the fecal discharge of
such an individual upon a vegetable diet will be much greater and may
even be as great as 350 grams and possess a solid content of 75 grams.
In the author's own experience the average daily output of moist feces,
calculated on the basis of data secured from the examination of over
1000 stools, was about 100 grams. The variation in the normal daily
output being so great renders this factor of very little value for diag-
nostic purposes, except where the composition of the diet is accurately
known. Lesions of the digestive tract, a defective absorptive function,
or increased peristalsis as well as an admixture of mucus, pus, blood,
and pathological products of the intestinal wall may cause the total
amount of excrement to be markedly increased. An idea of the varia-
tion of the percentage of dry matter in the feces evacuated after the
ingestion of different diets may be gathered from a consideration of the
following table. 1

1 Schmidt & Strasburger: "Die Fazes des Menschen", Berlin 1915





Dry Matter Percent.

Nursing infant . .








Potatoes . .


Mixed Diet

The fecal pigment of the normal adult is hydrobilirubin This,
pigment originates from the bilirubin which is secreted into the intes-
tine in the bile, the transformation from bilirubin to hydrobilirubin
being brought about through the activity of certain bacteria. Hydro-
bilirubin is sometimes called stercobilin
and bears a close resemblance to urobilin
or may even be identical with that pig-
ment. Neither bilirubin nor biliverdin
occurs normally in the fecal discharge of
adults, although the former may be de-
tected in the excrement of nursing in-
fants. If these pigments are found in
the feces of adults, they indicate an
abnormally rapid transit through the
large bowel thus preventing their trans-
formation into hydrobilirubin. Fre-
quently, in some way as yet unknown,
probably through the agency of certain bacterial processes, color-
less hydrobilirubinogen (leucohydrobilirubin) is formed which after
the passage of the movement and exposure to air is reconverted
into hydrobilirubin. This may explain in some cases the darken-
ing of the stool when exposed to the air. The most important
factor in determining the color of the fecal discharge is the diet. A
mixed diet, for instance, produces stools which vary in color from light
to dark brown, an exclusive meat diet gives rise to a brownish-black
stool, whereas the stool resulting from a milk diet is invariably light
colored. Certain pigmented foods, such as the chlorophyllic vegetables
and various varieties of berries, each afford stools having a characteristic
color. Certain drugs act in a similar way to color the fecal discharge.
This is well illustrated by the occurrence of green stools following the use
of calomel, of black stools after bismuth ingestion, and of yellow stools
following the administration of rhubarb, senna or santonin. The green



Color of crystals same as the color
of those in Fig. 56, page 205.


color of the calomel stool is generally believed to be due to biliverdin.
v. Jaksch, however, claims to have proven this view to be incorrect
since he was able to detect hydrobilirubin (or urobilin) but no biliverdtn
in stools after the administration of calomel. The bismuth stool was at
one time thought to derive its color from the black sulphide which is
formed from the subnitrate of bismuth. We now know 1 that the color
is due to the reduction of the bismuth compound (subnitrate) to bismuth
suboxide. In cases of biliary obstruction the grayish-white acholic
stool is formed.

Under normal conditions the odor of feces is due to skatole and
indole, two bodies formed in the course of putrefactive processes occur-
ring within the intestine (see page 212). Such bodies as methane,
methyl mercaptan, and hydrogen sulphide may also add to the disagree-
able character of the odor. The intensity of the odor depends to a
large degree upon the character of the diet, being very marked in stools
from a meat diet, much less marked in stools from a vegetable diet, and
frequently hardly detectable in stools from a milk diet. Thus the stool
of the infant is ordinarily nearly odorless and any decided odor may
generally be readily traced to some pathological source.

A neutral reaction ordinarily predominates in normal stools, although
slightly alkaline or even acid stools are met with. The acid reaction is
encountered much less frequently than the alkaline, and then commonly
only following a vegetable diet.

Experiments in which the actual hydrogen ion concentration of the
feces was determined indicate that the reaction of the excreta is uni-
formly slightly alkaline. 2 Pronounced dietary changes, e.g., low protein
diet, high protein diet, fasting, water drinking with meals, produce at
most only minor changes in the reaction of the feces.

The form and consistency of the stool is dependent, in large measure,
upon the nature of the diet. Under normal conditions the consistency
may vary from a thin, pasty discharge to a firmly formed stool. Stools
which are exceedingly thin and watery ordinarily have a pathological
significance. In general the feces of the carnivorous animals is of a
firmer consistency than that of the herbivora.

The continued ingestion of a diet which is very thoroughly digested
and absorbed is frequently accompanied by the formation of dry, hard
fecal masses (scybald). Constipation generally results, due to the small
bulk of the feces and its lack of moisture. At present the formation of
scybala is considered pathological, as an expression of spastic constipa-
tion. To counteract this tendency toward constipation the ingestion

1 Quincke: Munch, med. Woch., p. 854, 1896.

2 Howe and Hawk: Jour. Biol. Chem., n, 129, 1912.


of agar-agar 1 has been suggested. 2 This agar is relatively indigestible
and readily absorbs water (about 16 times its weight), thus forming a
bulky fecal mass which is sufficiently soft to permit of easy evacuation.
The function of agar is not limited to its use in connection with consti-
pation; it may serve in other capacities as an aid to intestinal therapeu-
tics by serving as a vehicle for certain drugs. 3

It is frequently desirable for clinical or experimental purposes to
make an examination of the fecal output which constitutes the residual
mass from a certain definite diet. Under such conditions, it is custom-
ary to cause the person under observation to ingest some substance, at
the beginning and end of the period in question, which shall sufficiently
differ in color and consistency from the surrounding feces as to render
comparatively easy the differentiation of the feces of that period from
the feces of the immediately preceding and succeeding periods. One
of the most satisfactory methods of making this " separation" is by
means of the ingestion of a gelatin capsule containing about 0.2 gram of
powdered charcoal at the beginning and end of the period under observa-
tion. This procedure causes the appearance of two black zones of char-
coal in the fecal mass and thus renders comparatively simple the
differentiation of the feces of the intermediate period. Carmine (0.3
gram) may be used in a similar manner and forms two dark red zones.
Some similar method for the "separation of feces" is universally
practised in connection with the scientifically accurate type of nutrition
or metabolism experiment which embraces the collection of useful data
regarding the income and outgo of nitrogen and other elements.

Among the macroscopical constituents of the feces may be men-
tioned the following: Intestinal parasites, undigested food particles,
gall stones, pathological products of the intestinal wall, enteroliths,
intestinal sand, and objects which have been accidentally swallowed.

The fecal constituents which at various times and under different
conditions may be detected by the use of the microscope are as follows :
Constituents derived from the food, such as muscle fibers, connective-
tissue shreds, starch granules, and fat; form elements derived from
the intestinal tract, such as epithelium, erythrocytes, and leucocytes;
mucus; pus corpuscles; parasites and bacteria. In addition to the con-
stituents named the following crystalline deposits may be detected:
cholesterol, koprosterol, soaps, fatty acid, fat, hematoidin, l( triple phos-

1 Agar-agar is a product prepared from certain types of Asiatic sea- weed. It is a carbo-
hydrate and is classified as a galactan in the polysaccharide group.

2 Mendel: Zent.f. ges. Physiol. u. Path, des Stofw., No. 17, p. i, 1908; Schmidt: Munch,
med. Woch., 52, 1970, 1905.

3 Einhorn: Berl. klin. Woch., 49, 113, 1912.


phate" Char cot-Ley den crystals, and the oxalate, carbonate, phosphate,
sulphate, and lactate of calcium. (See Figs. 64 to 69, pp. 230 and 231.)

The koprosterol of the feces is similar to cholesterol, and may be
formed by the reduction of the latter. It responds to cholesterol color
tests and has the same solubility, but possesses a lower melting-point
and crystallizes in fine needles instead of plates such as cholesterol

The detection of minute quantities of blood in the feces ("occult
blood") has recently become a recognized aid to a correct diagnosis of
certain disorders. In these instances the hemorrhage is ordinarily so
slight that the identification by means of macroscopical characteristics
as well as the microscopical identification through the detection of ery-
throcytes are both unsatisfactory in their results. Of the tests given
for the detection of "occult blood" the benzidine reaction and the
ortho-tolidin and hematein tests (page 233) are probably the most
satisfactory. Since "occult blood" occurs with considerable regularity
and frequency in gastrointestinal cancer and in gastric and duodenal
ulcer, its detection in the feces is of especial value as
an aid to a correct diagnosis of these disorders. Cer-
tain precautions are essential, such as the establish-
ment of a meat-free diet over a period of time before
the specimen is collected. (Feces from a meat diet
will give an occult blood reaction with some of the

most delicate tests.) Bleeding from the bowel such FIG. 62 CHARCOT-
. i , ., ,, j . , f LEYDEN CRYSTALS.

as is seen in hemorrhoids, as well as the admixture of

menstrual blood, is to be considered in the interpretation of the result.

It has been quite clearly shown that the intestine of the newly born
is sterile. However, this condition is quickly altered and bacteria may
be present in the feces before or after the first ingestion of food. There
are three possible means of infecting the intestine, i.e., by way of the
mouth or anus or through the blood. The infection by means of the
blood seldom occurs except under pathological conditions, thus limit-
ing the general infection to the mouth and anus.

In infants with pronounced constipation two-thirds of the dry sub-
stance of the stools has been found to consist of bacteria. In the stools
of normal adults probably about one-third of the dry substance is
bacteria. 1 The average excretion of dry bacteria in 24 hours for an
adult is about 8 grams. The output of fecal bacteria has been found
to undergo a decrease under the influence of water drinking with meals. 2

1 Schittenhelm and Tollens found bacteria to comprise 42 per cent of the dry matter.
This value is, however, undoubtedly too high.

2 Mattill and Hawk: Jour. Am. Chem. Soc., 33, 1999, 1911; Blatherwick and Hawk:
Bioch. Bull., 3, 28, 1913. ^



There was also a decrease in intestinal putrefaction, 1 a fact which
indicates that at least a part of the bacterial deficit was made up of
putrefactive organisms. In some cases over 50 per cent of the total
nitrogen of feces has been shown to be bacterial nitrogen. 2

Various enzymes have been detected in the feces. The first one so
demonstrated was pancreatic amylase. 3 The amylase content of the
feces is believed to be an index of the activity of the pancreatic function. 4
The excretion of this enzyme has been found to increase under the
influence of water drinking with meals. 5 Other enzymes which have
been found in the feces under various conditions are trypsin, rennin,
maltase, sucrase, lactase, nuclease and lipase. 6 In an abnormally rapid
transit of food through the intestinal tract, such as is seen in certain
diarrheas, nearly all of these enzymes may be detected.

Some of the more important organisms met with in the feces are the
following: 7 B. coli, B. lactis aerogenes, Bact. Welchii, B. bifidus, and
coccal forms. Of these the first three types mentioned are gas-forming
organisms. The production of gas by the fecal flora in dextrose-
bouillon is subject to great variations under pathological conditions;
alterations in the diet of normal persons will also cause wide fluctuations.
Data as to the production of gas are of considerable importance in a
diagnostic way, although the exact cause of the variations is not yet
established. It should be borne in mind in this connection that gas
volumes are frequently variable with the same individual. For this
reason it is necessary in every instance to follow the gas production for
a considerable period of time before drawing conclusions. 8 While the
question of the study of bacterial flora of the feces is a question beyond
the range of this work, mention may be made here of the character of
the organisms observed by Gram staining of the stool after administra-
tion of different types of diet. It has been shown that when the diet
is markedly protein, the protein type of flora becomes predominant in
the stools. Gram-stained smears show a fairly equal distribution of
Gram-negative and Gram-positive organisms. Among the latter are
largely the subtiloid organisms with some of the Bact. Welchii, together
with a moderate number of diplococci and coccoid forms. Most of the
Gram-negative organisms resemble the B. coli. When the diet is

1 Hattrem and Hawk: Arch. Int. Med., 7, 610, 1911; Blatherwick, Sherwin and Hawk:
loc. cit.

2 MacNeal, Latzer and Kerr: Jour. Inf. Dis., 6, 123, 1909; Mattill and Hawk: Jour.
Exp. Med., 14, 433, 1911; Blatherwick and Hawk: Biochem. Bull., 3, 28, 1913.

3 Wegscheider: Inaug. Diss., Strassburg, 1875.

4 Wohlgemuth: Berl. klin. Woch., 47, 3, 92, 1910.

5 Hawk: Arch. Int. Med., 8, 382, 1911.

6 Ury: Biochem. Zeit., 23, 152, 1909.

7 Herter and Kendall: Journal of Biological Chemistry, 5, 283, 1908.

8 Herter and Kendall: loc. cit.


carbohydrate the field is strongly Gram positive and has a more homo-
geneous appearance. The bacteria seen consist chiefly of long slender
Gram-positive rods -belonging to the B. acidophilus and B. bifidus
groups. 1

The nitrogen present in the feces consists principally of bacteria,
unabs orbed intestinal secretions, epithelial cells, mucus material and food
residues. In the early days of nutrition study the fecal nitrogen was
believed to consist principally of food residues. We now know that
such residues ordinarily make up but a small part of the nitrogen quota
of the stools of normal individuals who exercise normal mastication. 2
When meat has been "bolted," however, from J^ gram to 16 grams of
macroscopical meat residues has been found in a single stool. 3 The
phrase " metabolic product nitrogen" is frequently used as a designa-
tion for all fecal nitrogen except that present as food residues and
bacteria. Bacteria cannot logically be classed under " metabolic"
nitrogen since they doubtless develop at the expense of food nitrogen
as well as at the expense of that in the form of intestinal secretions.
In the accurate study of "protein utilization" 4 a correction should be
made for "metabolic nitrogen." Data regarding the output of meta-
bolic nitrogen may be secured by determining the fecal nitrogen excre-
tion on a diet of proper energy value but containing no nitrogen*
Agar-agar may be utilized advantageously in connection with such a
nitrogen-free diet.

Feces are still excreted from the intestine even when no food is
ingested. Carefully conducted fasting experiments have demonstrated
this. A dog nourished on an ordinary diet to which bone ash has been
added will excrete a grey feces. When fasted such an animal will, after
a few days, excrete a small amount of a greenish-brown mass, containing
no bone ash. These are fasting feces. It is of a pitch-like consistency
and turns black on contact with the air. 6 Adult fasting men have been
found to excrete 7-8 grams of feces per day, the daily nitrogen value
being about o.i gram. 7 No separating medium such as charcoal or
carmine (page 238) should be used in differentiating fasting feces.

In recent years the examination of feces for evidences of parasitism
(detection of parasites and their ova) has taken on an added importance.
The investigation of the hookworm has been particularly developed.

^ammidge: The Feces of Children and Adults, 1914, p. 126.

2 Kermauner: Zeit. fiir BioL, 35, 316, 1897.

3 Foster and Hawk : Jour. Am. Chem. Soc., 37, 1347, 1915.

4 The percentage of the ingested protein which is absorbed from the intestine. This
may be calculated by subtracting the metabolic nitrogen from the total fecal nitrogen and
dividing this value by the food nitrogen.

5 Tsuboi: Zeit. fur BioL, 35, 68, 1897; Mendel and Fine: Jour. Biol. Chem., n, 5, 1912.

6 Howe and Hawk: Jour. Am. Chem. Soc., 33, 215, 1911.

7 Howe, Mattill and Hawk: Ibid., 33, 568, 1911.


(For methods and discussion see Bulletin 135, Bureau of Animal Indus-
try, U. S. Department of Agriculture, 1911, M. C. Hall.)

For diagnostic purposes the macroscopical and microscopical exami-
nations of the feces ordinarily yield much more satisfactory data than

Online LibraryPhilip B. (Philip Bovier) HawkPractical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science → online text (page 24 of 70)