“The amount of water vapor given off by the lungs varies greatly according as the air is already more or less saturated with water. As the air in the stalls between decks is always saturated with water vapor, we may take the very lowest estimate for each animal, namely, 60 ounces in 24 hours, which for a cargo of 200 head would amount to over 93 gallons. And this is in addition to the exhalations from the skin and the bowel and kidney excretions. The air between decks is therefore constantly saturated with moisture which condenses and runs down in streams on every solid object. Among the ill effects of this saturation may be noted:”
“First. The saturation of the air with water vapor increases the exhalation of carbon dioxide from the lungs. This effect on the excretion of carbonic acid is usually so great as to counterbalance the tendency of warm air to reduce the production of this acid. This saturation, therefore, with water increases the danger of suffocation by the accumulation of the irrespirable carbon dioxide in the ship, unless the air is being constantly removed.”
“Second. The excess of moisture in the warm atmosphere hastens the decomposition of the organic matter derived from the lungs, skin, and manure. Sir Alexander Armstrong, head of the medical department of the British Navy, says: “There can be no more fertile source of disease among seamen, or, indeed, other persons, than the constant inhalation of a moist atmosphere, whether sleeping or waking; but particularly is this influence injurious when the moisture exists between a ship’s decks, where it may be at the same time more or less impure, and hot or cold, according to circumstances.” It has become an aphorism with sanitarians that “a damp ship is an unhealthy ship,” and many instances are adduced in which a sufficient renewal of the air between decks, with or without stoves to dry it, has transformed a naval pest-house into a salubrious vessel.”
“All such considerations must emphasize the demand for such a constant renewal of air between decks on steamers carrying cattle as shall serve to obviate all those conditions of ill-health, with congestion and inflammation of the lungs, as have proved in the past a serious drawback to our foreign cattle-trade. To accomplish this and at once remove from between decks the excess of carbon dioxide, of decomposing organic matter, and of humidity, and to furnish air approaching in purity and dryness that of the atmosphere outside, we can conceive of nothing more simple and effective than thorough ventilation by fan or heat extraction, as referred to below.” Report of the U. S. Treasury Cattle Commission, 1882.
The above quotations were written with special reference to cattle but the author reproduces them here as in principle applicable to horses as well.
In both horses and cattle treated as above it is common to find ingesta in the bronchia drawn in during the violent paroxysms of coughing. Here we have a direct mechanical irritant and a means of septic infection, highly calculated to induce unhealthy broncho-pneumonia. Williams quotes the case of a horse in which vomition was caused by an over dose of aconite, and a portion of the food entered the bronchi.
In this connection must be named the introduction into the bronchia of liquids forcibly administered to horses and cattle. In the horse the length of the soft palate enables him to hold liquids in the mouth during his pleasure, and among the expedients adopted to coerce him are the very dangerous ones of holding the nostrils and of pouring the liquid through the nose. When the nostrils are held the urgent demand for air leads to attempts to breathe through the mouth, and, whether he succeeds in this or not, the usual result is the drawing of a portion of the liquid into the lungs. When it is poured through the nose the animal cannot protect himself except by rapid gulping, and as he must breathe, a portion of the liquid is usually drawn into the lungs. Any irritant taken in this way will develop bronchitis, and some bland agents like melted lard are almost equally injurious. Cattle having a short palate can scarcely resist swallowing liquids that are poured into the mouth, but a cough with the succeeding quick inspiration will almost certainly draw a portion into the bronchia. To return to the influence of cold, exposed situations which receive the full force of cold winds, those from the north and west on the Atlantic slope are specially conducive to bronchitis. Exposure of newly clipped animals to stand without protection in winter or early spring, has the same tendency. Finally the inhalation of smoke or of heated and irritant gases and vapors, as in a burning building, is an effective factor.
Symptoms: In its mildest form bronchitis is a transient illness with some dullness, impaired appetite, hot, dry mouth, redness of the visible mucous membranes, a moderately strong, resonant cough, attended with slight pain, slight rise of temperature, accelerated breathing and pulse, and mucous discharge from the nose. Such an attack passes over in a few days and without any medicinal treatment if ordinary precautions are taken to avoid a repetition of its causes.
In severe cases the symptoms are more intense from the first. Besides the dullness and inappetence, hot, dry mouth, generally increased temperature of the body (102° to 104° F.), accelerated and labored breathing, and other manifestations of fever, there are more specific symptoms. The cough is dry, hard, painful, often paroxysmal, and appears as if it came from the very depth of the chest. A strong, harsh, bronchial sound is heard over the lower end of the trachea and the upper border of the middle third of the chest just behind the shoulder. Percussion detects no change from the natural resonance of the chest, nor auscultation any crepitating sound. Pressure in the intercostal spaces causes no suffering. The expired air feels hot. The pulse though accelerated is moderately soft and sometimes even weak, a condition which marks inflammations of mucous membranes as contrasted with those of the serous. The mucous membrane of the nose has a dark red hue, especially when the inflammation extends to the smaller ramifications of the bronchial tubes so as to impair the æration of the blood. In the same state there is excessive dullness and prostration because of the supply of partially venous blood to the brain. The head is held low, the nose often supported upon the manger, and the eyelids are semi-closed and injected.
From the second to the fourth day a free exudation takes place from the surface of the mucous membrane, and the symptoms are materially changed. The cough becomes more frequent but softer, looser, and attended with a rattle from the air passing through the abundant mucous secretion. The cooing or tubal sound heard at the lower end of the windpipe and behind the shoulder has now given place to a mucous râle. A nasal discharge appears at first watery, thin, of a whitish, glairy froth, but soon becoming more opaque, white, milky and flocculent and having little tendency to stick to the nostrils. This is often expelled with sneezing and accompanied by movement of the jaws. With the access of free secretion there is a great mitigation of the fever and the other distressing symptoms, and, if no relapse nor complication supervenes, recovery may be complete in a fortnight or three weeks from the onset.