Encyclopaedia Britannica > Volume 19, PHY-PRO

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occurs as an accompaniment or sequel of bronchitis either
from the inflammation passing from the finer bronchi to
the pulmonary air vesicles, or from its affecting portions of
lung which have undergone collapse. It occurs most
frequently in children, and is often connected with some
pre-existing acute ailment in which the bronchi are
implicated, such as measles or hooping cough. It likewise
affects adults and aged people in a more chronic form
as the result of bronchitis. Sometimes a condition of
catarrhal pneumonia may be set up by the plugging of one
or more branches of the pulmonary artery, as may occur in
heart disease, pyaemia, &c.
The symptoms characterizing the onset of catarrhal pneumonia
in its more acute form are the occurrence during an attack of
bronchitis of a sudden and marked elevation of temperature, to¬
gether with a quickened pulse and increased difficulty in breathing.
The cough becomes short and painful, and there is little or no ex¬
pectoration. The physical signs are not distinct, being mixed up
with those of the antecedent bronchitis; but, should the pneumonia
be extensive, there may be an impaired percussion note with tubular
breathing and some bronchophony.
Acute catarrhal pneumonia must be regarded as a condition of
serious import. It is apt to run rapidly to a fatal termination, but
on the other hand a favourable result is not unfrequent if it is re¬
cognized in time to admit of efficient treatment. In the more
chronic form it tends to assume the characters of chronic phthisis
(see Phthisis). The treatment is essentially that for the more
severe forms of bronchitis (see Bronchitis), where, in addition to
expectorants, together with ammoniacal, ethereal, and alcoholic
stimulants, the maintenance of the strength by good nourishment
and tonics is clearly indicated. The breathing may often be re¬
lieved by light warm applications to the chest and back. Con¬
valescence is often prolonged, and special care wilhalways be required
in view of the tendency of the disease to develop into phthisis.
Chronic Interstitial Pneumonia or Cirrhosis of the Lung
is a slow inflammatory change affecting chiefly one portion
of the lung texture, viz., its fibrous stroma.
The changes produced in the lung by this disease are
marked chiefly by the growth of nucleated fibroid tissue
around the walls of the bronchi and vessels, and in the
intervesicular septa, which proceeds to such an extent as
to invade and obliterate the air cells. The lung, which is
at first enlarged, becomes shrunken, dense in texture, and
solid, any unaffected portions being emphysematous; the
bronchi are dilated, the pleura thickened, and the lung
substance often deeply pigmented, especially in the case of
miners, who are apt to suffer from this disease. In its
later stages the lung breaks down, and cavities form in its
substance as in ordinary phthisis.
This condition is usually present to a greater or less
degree in almost all chronic diseases of the lungs and
bronchi, but it is specially apt to arise in an extensive form
from pre-existing catarrhal pneumonia, and not unfre-
quently occurs in connexion with occupations which
necessitate the habitual inhalation of particles of dust, such
as those of colliers, flax-dressers, stonemasons, millers, &c.
The symptoms are very similar to those of chronic phthisis (see
Phthisis), especially increasing difficulty of breathing, particularly
on exertion, cough either dry or with expectoration, sometimes
copious and fetid. In the case of coal-miners the sputum is black
from containing carbonaceous matter.
The physical signs are deficient expansion of the affected side —
the disease being mostly confined to one lung—increasing dulness
on percussion, tubular breathing, and moist sounds. As the disease
progresses retraction of the side becomes manifest, and the heart
and liver may be displaced. Ultimately the condition both as
regards physical signs and symptoms takes the characters of the
later stages of phthisis with colliquative symptoms, increasing
emaciation, and death. Occasionally dropsy is present from the
heart becoming affected in the course of the disease. The malady
is usually of long duration, many cases remaining for years in a
stationary condition and even undergoing temporary improvement
111 weather, but the tendency is on the whole downward.
ihe treatment is conducted on similar principles to those
applicable in the case of phthisis. Should the malady be con¬
nected with a particular occupation, the disease might be averted
oi at least greatly modified by early withdrawal from such source
ot irritation. f T O A 1
-P O 251
PNOM PENH, the capital of Cambodia (see vol. iv.
p. 725).
PO, the largest river of Italy, traverses the whole length
of the great plain between the Alps and the Apennines,
which was in the Miocene period an arm of the sea con¬
necting the Adriatic with the Mediterranean by what is
now the Col d’Altare or Col di Cadibona and has gradually
been filled by detritus from the surrounding highlands.
That its course lies much nearer the Apennines than the
Alps is evidently due to the fact that the tributaries from
the loftier range on the north, whether in the form of
glacier or stream, have all along been much more powerful
than the tributaries from the south. The total length of
the river from its conventional source to the mouth of the
principal channel is 417 J miles, and the area of its basin,
which includes portions of Switzerland and Austria, is
estimated at 26,798 square miles. The general course of
the river has been already described in Italy (vol. xiii.
p. 435).
The Po forms a very extensive delta, and is probably
one of the most active of all rivers in the work of denuda¬
tion. Prony has calculated that between 1200 and 1600
the delta advanced at the rate of 80 feet per annum; and
between 1600 and 1804 the rate is said to have been as
much as 230 feet. This advance has naturally been
attended by great changes in the course and size of the
several channels. Ravenna, for example, once a great
port, now stands on dry land 4 miles from the sea. The
modern lagoons of Comacchio, which stretch southwards
from the delta, are being artificially reclaimed by the help
of the alluvial deposits.
In its ordinary condition the Po has a depth between Pancalieri
and the mouth of the Ticino of from 6 to 10 feet, and between the
mouth of the Lambro and that of the Adda of about 14 or 15 feet.
Lower down the depth occasionally exceeds 40 feet. Permanent
fords exist only in the upper Po, and between the mouths of
the Ticino and the Lambro. In times of great drought the bed
is quite dry at Rovello, and fords appear below Casalmaggiore and
at Borgoforte, where the French and Germans crossed in 1796,
1807, 1813, and 1814 ; but in general the river forms a complete
barrier both to foot and horse. The principal points where crossing
is effected by ferries or bridges are *Moncalieri, Turin, *Casale
Monferrato, Frassinato, *Valenza, *Mezzana Corti, *Piacenza,
Cremona, Casalmaggiore, Brescello, * Borgoforte, San Benedetto,
Ostiglia, *Occhiobello, Pontelagoscuro, Francolino. Railway
bridges exist at the places distinguished by an asterisk.
The river in general is at its fullest in May and June, and at its
lowest in January (see details in Lombardini’s elaborate study on
the lower Po in Memorie del Reale Istituto Lombardo, Milan,
1870). The ordinary floods on the Po are attended with little
danger ; but at intervals sometimes of a few sometimes of many
years they become events of the gravest national concern. Those
of 1651 and 1705 are among the most destructive recorded in
history, and in the present century the more memorable are those
of 1839, 1846, 1855, 1857, 1868, 1872, and 1879. In 1872 1150
square miles of country between the Reno and the Adige were
submerged, the district about Modena was turned into a lake,
the people of Revere saved the rest of their town only by sacri¬
ficing the front row of houses to form a temporary embankment,
and it was only by the wisely conducted energy of its inhabit¬
ants that Ostiglia was kept from destruction. During April
and May 1879 the rainfall was exceptionally heavy, the quan¬
tity for May alone being equal to more than a third of the an¬
nual total. The result was a rise in all the tributaries of the Po,
and on May 30 the flood in the main river was 21 feet above low
water at Mezzana Corta. A breach 720 feet long in the embank¬
ment between Bonizzo and Borgofranco caused the submergence of
155 square miles in the provinces of Mantua, Modena, and Ferrara,
and involved in its repair a national expenditure of £53,460.
Of the £5,902,981 devoted by the Government to the regulation
of the rivers of Italy in the twenty years 1861-1880, £2,257,872
had to be appropriated to the Po and its tributaries. Nowhere in
Europe except in Holland has the system of embankment been
carried to such perfection on so extensive a scale. A wide bed for
the river at its height is enclosed for long distances by a massive
master-dyke or froldo, and in the space between this and the ordi¬
nary channels suitable areas are often enclosed by secondary dykes
or golene. The following figures show the extent of the system in
1880