diet of bread, together with cylindrical epithelium in a state of partial
solution, from the intestinal canal, and occasional drops of oil.
Cholesterin is very rare. The less the mucus is mixed with the faeces,
the lower the part of the intestine from which it was derived
(Nothnagel).

(5.) After a milk diet and also after a fatty diet, crystalline needles
of lime, combined with fatty acids, chalk-soaps, constantly occur, even
in sucklings (Wegscheider). Even unchanged masses of casein and
fat occur during the milk-cure. Compounds of ammonia, with the
acids mentioned at p. 375, the result of putrefaction, belong to the
faecal matters (Brieger).

(6.) Amongst inorganic residues, soluble salts rarely occur in the
faeces because they diffuse readily e.g., common salt, and the other
alkaline chlorides, the compounds of phosphoric acid, and some of those
of sulphuric acid. The insoluble compounds, of which ammoniaco-
magnesic or triple phosphate, neutral calcic phosphate, yellow coloured
lime salts, calcium carbonate, and magnesium phosphate are the chief,
form 70 p.c. of the ash. Some of these insoluble substances are derived
from the food, as lime from bones, and in part they are excreted after
the food has been digested, as ashes are eliminated from food which
has been burned.

The excretion of inorganic substances is sometimes so great, that
they form incrustations around other faecal matters. Usually
ammoniaco-magnesic phosphate occurs in large crystals by itself, or it
may be mixed with magnesium phosphate.

(7.) A considerable portion of normal faecal matter consists of
micrococci and microbacteria (Bacterium termo Woodward, Noth-
nagel). Bacillus subtilis is not very plentiful, while yeast is seldom
absent (Frerichs, Nothnagel). In stools that contain much starch, the
bacillus amylobacter, which is tinged blue with iodine, occurs (p. 374),



380 PATHOLOGICAL VARIATIONS OF DIGESTION.

and other small globular or rod-like fungi, which give a similar reaction
(Nothnagel, Uffelmann). Bienstock, who has devoted attention to the
microbes of the faeces, finds two kinds of bacteria in all faeces ; both
resemble B. subtilis (Fig. 148) very closely, but they are distinguished
from it by their mode of development. They do not cause any
fermentative action. There are several other forms found in the faecal
evacuations, under different circumstances.

The changes of the intestinal contents have been studied on persons with <an
accidental intestinal fistula, or an artificial anus.

186, Pathological Variations.

A. The taking Of food may be interfered with by spasm of the muscles of
mastication (usually accompanied by general spasms), stricture of the oeso-
phagus, by cicatrices after swallowing caustic fluids (e.g., caustic potash, mineral
acids), or by the presence of a tumour, such as cancer. Inflammation of all kinds
in the mouth or pharynx interferes with the taking of food. Impossibility of
swallowing occurs as part of the general phenomena in disease of the medulla
oblongata, in consequence of paralysis of the motor centre (superior olives) for the
facial, vagus, and hypoglossal nerves, and also for the afferent or sensory fibres of
the gloss-pharyngeal, vagus, and trigeminus. Stimulation or abnormal excitation
of these parts causes spasmodic swallowing, and the disagreeable feeling of a
constriction in the neck (globus hystericus).

B. The secretion Of Saliva is diminished during inflammation of the salivary
glands; occlusion of their ducts by concretions (salivary calculi); also by the use of
atropin, daturin, and during fever, whereby the secretory (not the vaso-motor)
fibres of the chorda appear to be paralysed (p. 287). When the fever is very high, no
saliva is secreted. The saliva secreted during moderate fever is turbid and thick,
and usually acid. As the fever increases, the diastatic action of the saliva
diminishes (Uffelmann). The secretion is increased, by stimulation of the buccal
nerves (inflammation, ulceration, trigeminal neuralgia), so that the saliva is
secreted in great quantity. Mercury and jaborandi cause secretion of saliva, the
former causing stomatitis, which excites the secretion of saliva reflexly. Even
diseases of the stomach accompanied by vomiting, cause secretion of saliva. A
very thick tenacious sympathetic saliva occurs when there is violent stimulation
of the vascular system during sexual excitement, and also during certain psychical
conditions. The reaction of the saliva is acid in catarrh of the mouth, in fever
in consequence of decomposition of the buccal epithelium, and in diabetes mellitus
in consequence of acid fermentation of the saliva which contains sugar. Hence,
diabetic persons often suffer from carious teeth. Unless the mouth of an infant
be kept scrupulously clean, the saliva is apt to become acid.

C. Disturbances in the activity of the musculature of the stomach may be due
to paralysis of the muscular layers, whereby the stomach becomes distended, and
the ingesta remain a long time in it. A special form of paralysis of the stomach is
due to non-closure of the pylorus (Ebstein). This may be due to disturbances of
innervation of a central or peripheral nature, or there may be actual paralysis of
the pyloric sphincter, or anaesthesia of the pyloric mucous membrane, which acts
reflexly upon the sphincter muscle; and lastly, it may be due to the reflex
impulse not being transferred to the efferent fibre within the nerve centre.
Abnormal activity of the gastric musculature hastens the passage of the ingesta.
into the intestine ; vomiting often occurs.



DIGESTION DURING FEVER AND ANEMIA. 381

Gastric digestion is delayed by violent bodily or mental exercise, and some-
times it is arrested altogether. Sudden mental excitement may have the same
effect. These effects are very probably caused through the vaso-motor nerves of
the stomach. Feeble and imperfect digestion may be of a purely nervous nature
(Dyspepsia nervosa Leube ; Neurasthenia gastrica Burkart). [According to
J. W. Fraser, all infused beverages, tea, coffee, cocoa, retard the peptic digestion
of proteids, with few exceptions. The retarding action is less with coffee than
with tea. The tannic acid and volatile oil seem to be the retarding ingredients in
teas.]

Inflammatory or catarrhal affections of the stomach, as well as ulceration

and new formations, interfere with digestion, and the same result is caused by
eating too much food which is difficult of digestion, or taking too much highly
spiced sauces or alcohol. In the case of a dog suffering from chronic gastric catarrh,
Griitzner observed that the secretion took place continuously, and that the gastric
juice contained little pepsin, was turbid, sticky, feebly acid, and even alkaline.
The introduction of food did not alter the secretion, so that in this condition the
stomach really obtains no rest. The chief cells of the gastric glands were turbid.
Hence, in gastric catarrh, we ought to eat frequently, but take little at a time,
while at the same time dilute (0'4 p.c.) hydrochloric acid ought to be adminis-
tered. Small doses of common salt seem to aid digestion. [In cases of carcinoma
of the stomach, the acid reaction of the gastric juice is almost invariably absent.]

Feeble digestion may be caused either by imperfect formation of acid or
pepsin, so that both substances may be administered in such a condition. [It
may also be due to deficient muscular power in the wall of the stomach.] In
other cases, lactic, butyric, and acetic acids are formed, owing to the presence of
lowly organisms. In such cases, small doses of salicylic acid are useful (Hoppe-
Seyler), together with some hydrochloric acid. Pepsin need not be given often,
as it is rarely absent, even from, the diseased gastric mucous membrane. Albumin
has been found in the gastric juice in cases of gastric catarrh and cholera.

D. Digestion during Fever and Anaemia. Beaumont found that in the

case of Alexis St. Martin, when fever occurred, a small amount of gastric juice
was secreted ; the mucous membrane was dry, red, and irritable. Dogs suffering
from septicsemic fever, or rendered anaemic by great loss of blood, secrete gastric juice
of feeble digestive power and containing little acid (Manassem). Hoppe-Seyler
investigated the gastric juice of a typhus patient, in which Von der Velden found
no free acid, and he found the same in gastric catarrh, fever, and in cancer of the
stomach. The gastric juice of the tj'phus patient did not digest artificially, even
after the addition of hydrochloric acid. The diminution of acid, under these cir-
cumstances, favours the occurrence of a neutral reaction, so that, on the one hand,
digestion cannot proceed, and, on the other, fermentative processes (lactic and
butyric acid fermentations with the evolution of gases) occur. These results are
associated with the presence of micro-organisms and Sarcina ventriculi (Goodsir).
He advises the administration of hydrochloric acid and pepsin, and when there
are symptoms of fermentation, small doses of salicylic acid. Uffelmann found the
secretion of a peptone-forming gastric juice ceased in fever, when the fever is
severe at the outset, when a feeble condition occurs, or when the temperature is
very high. The amount of juice secreted is certainly diminished during fever.
The excitability of the mucous membrane is increased, so that vomiting readily
occurs. The increased excitability of the vaso-motor nerves during fever (Heiden-
hain) is disadvantageous for the secretion of the digestive fluids. Beaumont
observed that fluids are rapidly absorbed from the stomach during fever, but the
absorption of peptones is diminished on account of the accompanying catarrhal
condition of the stomach, and the altered functional activity of the muscularis
mucosse (Leube).

Many salts when given in large amount disturb gastric digestion e.g., the



382 CONSTIPATION AND DIARRHCEA.

sulphates. While the alkaloids, morphia, strychnia, digitalin, narcotin, veratria
have a similar action ; quinine favours it (Wolberg). In some nervous individuals
a " peristaltic un-rest of the stomach," conjoined with a dyspeptic condition, occurs
(Kussmaul).

E. In acute diseases, the secretion of bile is affected ; it becomes less in amount
and more watery, i.e., it contains less specific constituents. If the liver undergoes
great structural change, the secretion may be arrested.

F. Gallstones. When decomposition of the bile occurs, gallstones are formed
in the gall-bladder or in the bile-ducts. Some are white, and consist almost entirely
of stratified layers of crystals of cholesterin. The brown forms consist of bilirubin-
lime and calcium carbonate, often mixed with iron, copper, and manganese. The
gallstones in the gall-bladder become facetted by rubbing against each other. The
nucleus of the white stones often consists of chalk and bile colouring matters,
together with nitrogenous residues, derived from shed epithelium, mucin, bile salts
and fats. Gallstones may occlude the bile-duct and cause chola3mia. When a
small stone becomes impacted in a duct, it gives rise to excessive pain constituting
hepatic colic, and may even cause rupture of the bile-duct with its sharp edges.

G. Nothing certain has been determined regarding the pancreatic secretion
in disease, but in fever, it appears to be diminished in amount and digestive
activity. The suppression of the pancreatic secretion [as by a cancerous tumour
of the head of the pancreas] is often accompanied by the appearance of fat in the
form of globules or groups of crystals in the faeces.

H. Constipation is a most important derangement of the digestive tract. It
may be caused by 1. Conditions which obstruct the normal channel, e.g., con-
striction of the gut from stricture in the large gut after dysentery, tumours,
rotation on its axis of a loop of intestine (volvulus), or invagination, occlusion
of a coil of gut in a hernial sac, or by the pressure of tumours or exudations
from without, or congenital absence of the anus. 2. Too great dryness of
the contents, caused by too little water in the articles of diet, diminution
of the amount of the digestive secretions, e.g., of bile in icterus; or in
consequence of much fluid being given off by other organs, as after copious
secretion of saliva, milk, or in fever. 3. Variations in the functional activity of
the muscles and motor-nervous apparatus of the gut may cause constipation, owing
to imperfect peristalsis. This condition occurs in inflammations, degenerations,
chronic catarrh, diaphragmatic inflammation. Affections of the spinal cord, and
sometimes also of the brain, are usually accompanied by slow evacuation of the
intestine. Whether diminished mental activity and hypochondrias are the cause
of or are caused by constipation is not proved. Spasmodic contraction of a part of
the intestine may cause temporary retention of the intestinal contents, and, at the
same time, give rise to great pain or colic ; the same is true of spasm of the anal
sphincter, which may be excited reflexly from the lower part of the gut. The
faecal masses in constipation are usually hard and dry, owing to the water being
absorbed ; hence they form large masses or scybala within the large intestine, and
these again give rise to new resistance.

Amongst the reagents which prevent evacuation of the bowels, some paralyse the
motor apparatus temporarily, e.g., opium, morphia; some diminish the secretion of
the intestinal mucous membrane, and cause constriction of the blood-vessels, as
tannic acid, vegetables containing tannin, alum, chalk, lead acetate, silver nitrate,
bismuth nitrate.

I. Increased evacuation of the intestinal contents is usually accompanied by a
watery condition of the faeces, constituting diarrhoea.

The causes are :

1. A too rapid movement of the contents through the intestine, chiefly through
the large intestine, so that there is not time for the normal amount of absorption
to take place. The increased peristalsis depends upon stimulation of the motor-



COMPARATIVE PHYSIOLOGY OF DIGESTION. 383

nervous apparatus of the intestine, usually of a reflex nature. Rapid transit of the
contents through the intestine causes the evacuation of certain substances, which
cannot be digested in so short a time.

2. The stools become thinner from the presence of much water, mucus, and the
admixture with fat, and by eating fruit and vegetables. In rare cases, when the
evacuations contain much mucin, Charcot's crystals (Fig. 115, c) occur. In ulcera-
tion of the intestine, leucocytes (pus) are present (Nothnagel).

3. Diarrhoaa may occur as a consequence of disturbance of the diffusion-processes
through the intestinal walls, as in affections of the epithelium, when it becomes
swollen in inflammatory or catarrhal conditions of the intestinal mucous membrane.
[Irritation over the abdomen, as from the subcutaneous injection of small quan-
tities of saline solutions, causes diarrhoea (M. Hay).]

4. It may also be due to increased secretion into the intestine, as in capillary
diffusion, when magnesium sulphate in the intestine attracts water from the
blood.

The same occurs in cholera, when the stools are copious and of a rice-water
character, and are loaded with epithelial cells from the villi. The transudation
into the intestine is so great that the blood in the arteries becomes very thick,
and may even on this account cease to circulate.

Transudation into the intestine also takes place as a consequence of paralysis of
the vaso-motor nerves of the intestine. This is perhaps the case in diarrhoea
following upon a cold. Certain substances seem directly to excite the secretory
organs of the intestines or their nerves, such as the drastic purgatives (p. 364).
Pilocarpin injected into the blood causes great secretion (Masloff).

During febrile conditions, the secretion of the intestinal glands seems to be
altered quantitatively and qualitatively, with simultaneous alteration of the
functional activity of the musculature and the organs of absorption, while the
excitability of the mucous membrane is increased (Uffelmann). It is important to
note that in many acute febrile diseases, the amount of common salt in the urine
diminishes, and increases again as the fever subsides.



187. Comparative.



Salivary Glands. Amongst Mammals the herbivora have larger salivary
glands than the carnivora ; while midway between both are the omnivora. The
whale has no salivary glands. The pinnipedia have a small parotid, which is
absent in the echidna. The dog and many carnivora have a special gland lying
in the orbit, the orbital or'zygomatic gland. In Birds the salivary glands open at
the angle of the mouth, in them the parotid is absent. Amongst Reptiles the
parotid of some species is so changed as to form poison glands ; the tortoise has
sublingual glands ; reptiles have labial glands. The Amphibia and Fishes have
merely small glands scattered over the mouth. The salivary glands are large in
Insects ; some of them secrete formic acid. The salivary glands are well de-
veloped in molluscs, and the saliva of dolium galea contains more than 3 p. c. of
free sulphuric acid (?) The cephalopods have double glands.

A Crop is not present in any mammal ; the stomach is either simple, as in man,
or, as in many rodents, it is divided into two halves, into a cardiac and a pyloric
portion. The stomach of ruminants is compound, and consists of four cavities.
The intestine is short in flesh-eating animals and long in herbivora. The caecum is
a very large and important digestive organ in herbivora, and in most rodents;
it is small in man, and absent in carnivora. The oesophagus in grain-eating
Birds not unfrequently has a blind diverticulum or crop for softening the food.
In the crop of pigeons during the breeding season, there is formed a peculiar
secretion "pigeon's milk," which is used to feed the young (J. Hunter). The



384 HISTORICAL ACCOUNT OF DIGESTION.

stomach consists of a glandular proventriculus and a strong muscular stomach
which is covered with horny epithelium and triturates the food. There are
usually two fluid diverticula on the small intestine near where it joins the large
gut. In Fishes the intestinal canal is usually simple ; the stomach is merely a
dilatation of the tube ; and at the pylorus there may be one, but usually many,
blind glandular appendages (the appendices pyloricse). There are usually longi-
tudinal folds in the intestinal mucous membrane, but in some fishes, e.g. t the shark,
there is a spiral valve. [It is curious to find that the inversive (cane-sugar) fer-
ment is wanting in the herbivora, as the cow, horse, and sheep, but is present in
the carnivora, as the dog and cat. It is also met with in birds and reptiles, and
in many of the invertebrates, as the ordinary earth-worm (Matthew Hay).]

In Amphibia and Reptiles the stomach is a simple dilatation; the gut is larger
in vegetable feeders than in flesh feeders. The liver is never absent in vertebrates,
although the gall-bladder frequently is. The pancreas is absent in some fishes.

Digestion in Plants. The observations on the albumin-digesting power of
some plants (Canby, 1869; Ch. Darwin, 1875) are extremely interesting. The
sundew or drosera has a series of tentacles on the surface of its leaves, and the
tentacles are provided with glands. As soon as an insect alights upon a leaf it is
suddenly seized by the tentacles, the glands pour out an acid juice over the prey,
which is gradually digested ; all except the chitinous structures. The secretion, as
well as the subsequent absorption of the products of digestion, are accomplished by
the activity of the protoplasm of the cells of the leaves. The digestive juice con-
tains a pepsin-like ferment and formic acid. Similar phenomena are manifested
by the Venus flytrap (Dionsea), by pinguicula, as well as by the cavity of the
altered leaves of nepenthes. About fifteen species of these " insectivorous" or
carnivorous plants are known.

188. Historical.

Digestion in the Mouth. The Hippocratic school was acquainted with the
vessels of the teeth ; Aristotle ascribed an uninterrupted growth to these organs, and
he farther noticed that animals that were provided with horns, and had cloven
hoofs, had an imperfect set of teeth the upper incisors were absent. It is curious
to note that in some cases where men have had an excessive formation of hairy
appendages, the incisor teeth have been found to be badly developed. The muscles
of mastication were known at an early period ; Vidius (t!567) described the tempero-
maxillary articulation with its meniscus. The older observers regarded the saliva
as a solvent, and in addition, many bad qualities, especially in starving animals,
were ascribed to it. This arose from the knowledge of the saliva of mad animals,
and the parotid saliva of poisonous snakes. Human saliva, without organisms, is
poisonous to birds (Gautier). The salivary glands have been known for a long
time. Galen (131-203 A.D.) was acquainted with Wharton's duct, and Ae'tius
(270 A.D. ) with the sub-maxillary and sub-lingual glands. Hapel de la Chenaye (1780)
obtained large quantities of saliva from a horse, in which he was the first to make a
salivary fistula. Spallanzani (1786) asserted that food mixed with saliva was
more easily digested than food moistened with water. Hamberger and Siebold
investigated the reaction, consistence, and specific gravity of saliva, and found in
it mucus, albumin, common salt, calcium, and sodium phosphates. Berzelius
gave the name ptyalin to the characteristic organic constituent of saliva, but
Leuchs (1S31) was the first to detect its diastatic action.

Gastric Digestion. Digestion was formerly compared to boiling, whereby
solution was effected. According to Galen, only, substances that have been dis-
solved passed through the pylorus into the intestine. He described the move-
ments of the stomach and the peristalsis of the intestines. Aelian gave names to



HISTORICAL. 385

the four stomachs of the ruminants. Vidius (t 1567) noticed the numerous small
apertures of the gastric glands. Van Helmont (f 1644) expressly notices the
acidity of the stomach. Eeaumur (1752) knew that a juice was secreted by the
stomach, which effected solution, and with which he and Spallanzani performed
experiments on digestion outside the body. Carminati (1785) found that the
stomachs of carnivora during digestion secreted a very acid juice. Prout (1824)
discovered the hydrochloric acid of the gastric juice, Sprott and Boyd (1836) the
glands of the gastric mucous membrane, while Wasmann and Bischoff noted the two
kinds of gastric glands. After Beaumont (1834) had made his observations upon
Alexis St. Martin, who had a gastric fistula, caused by a gunshot wound, Bassow
(1842) and Blondlot (1843) made the first artificial gastric fistulse upon animals.
Eberle (1834) prepared artificial gastric juice. Mialhe called albumin, when
altered by gastric digestion, albuminose; Lehmann, who investigated this sub-
stance more carefully, gave it the name peptone. Schwann isolated pepsin (1836),
and established the fact of its activity in the presence of hydrochloric acid.

Pancreas, Bile, Intestinal Digestion. The pancreas was known to the

Hippocratic School; Maur. Hoffmann (1642) demonstrated its duct (fowl), and
Wirsung described it in man. Regner de Graaf (1664) collected the pancreatic
juice from a fistula, and Tiedmann and Gmelin found it to be alkaline, while
Leuret and Lassaigne found that it resembled saliva. Valentin discovered its
diastatic action, Eberle its emulsionising power, and Cl. Bernard (1846) its tryptic
and fat- splitting properties. The last-mentioned function was referred to by
Purkinje and Pappenheim (1836).

Aristotle characterised the bile as a useless excretion; according to Erasistratus
(304 B.C.), fine invisible channels conduct the bile from the liver into the gall-
bladder. Aretaeus ascribed icterus to obstruction of the bile-duct. Benedetti
(1493) described gall-stones. According to Jasolinus (1573), the gall-bladder is
emptied by its own contractions. Sylvius de la Boe noticed the lymphatics of the
liver (1640); Walaeus, the connective-tissue of the so-called capsule of Glisson
(1641). Haller indicated the uses of bile in the digestion of fats.

The liver-cells were described by Henle, Purkinje, and Dutrochet (1838).
Heynsius discovered the urea, and Cl. Bernard (1853) the sugar in the liver, and he
and Hensen (1857) found glycogen in the liver. Kiernan gave a more exact descrip-
tion of the hepatic blood-vessels (1834). Beale injected the lymphatics, and Gerlach