Metathorax

“ Minute Insects with slender, thread-like, or hair-like antennae; four delicate membranous wings, the front pair of which are the larger; their neuration is not abundant and is irregular, so that the cells are also irregularly arranged; the transverse nervules are only one or two in number. [306] Prothorax very small, in the winged forms quite concealed between the head and the large mesothorax; this latter closely connected with, or fused with, the metathorax. Species quite wingless, or with wings unfitted for flight, exist ”

“ The irritating effects of gas, unless it comes in small quantities through the ribs from wounds in the chest-walls, are very frequently followed in a short time by the production of a quantity of serosity or of pus. If air is introduced into the pleural cavity from perforation of the lung, there is also liquid matter from the lungs of such a character as at once to provoke inflammatory action. Such a condition is then denominated hydro-pneumothorax or pyo-pneumothorax. The latter was, in fact, recognized by Hippocrates by the sign of succussion, though not so designated. ”

“ Why is it necessary to introduce air into the lungs?"
"Yes," said Miette; "let us pass to that."
"The blood, in going out of the heart, circulates to all the parts of the body in order to make necessary repairs; at the same time it charges itself with all the old matter which has been used up and is no longer any good and carries it along. Now, what is it going to do with this old matter? It will burn it. Where will it burn it? In the lungs. Now, there can be no combustion when there is no air. ”

“ If a circumscribed pneumothorax was present with phthisis, the diagnosis might be difficult. Powell calls attention to the similarity of some of the signs of acute congestion rapidly supervening at the base of a comparatively sound lung to those of pneumothorax. But in the former the resonance, although high-pitched, is not truly tympanitic, and the heart is not displaced. There is no other disease of the chest where we find in such close proximity the two extremes of percussion sounds—flatness from the secondary effused fluid, and the tympanitic resonance above. ”

“ Hæmothorax, even of considerable severity, will undergo spontaneous cure. An early rise of temperature may be disregarded.
(ii) Tapping the chest is indicated when pressure signs on the lung are sufficiently severe to cause serious symptoms, and the removal of the blood undoubtedly shortens the period of recovery, as well as relieves symptoms.
In such cases the collection of blood has usually been rapid and continuous; hence a fresh hæmorrhage is always probable when the local pressure has been removed. ”

“ Pneumothorax is the only pathologic condition associated with signs similar to those of expiratory, valve-like bronchial obstruction by a foreign body.
3. Partial bronchial obstruction by an object such as a nail allows air to pass to and fro with some degree of retardation, and impairs the drainage of the subjacent lung. Limitation of expansion will be found on the invaded side. The area below the foreign body will give an impaired percussion note. Breath-sounds are diminished in the area of dullness, and vocal resonance and fremitus are impaired. Rales are of great diagnostic import ”

“ Pneumothorax means an effusion of air and of the matter of a tubercular abscess from disease into the cavity of the chest, or from an injury or a wound in the lung. When pneumothorax is the consequence of disease of long standing, the patient may be sensible of a sudden pain, which does not abate, and which is accompanied by an equally sudden increase of the difficulty of breathing, for which he cannot account. ”

“ The two lungs must, therefore, be alternately affected as to their capacity according as the heart occupies space on either side of the thorax. In expiration, the heart, E, is more uncovered by the shelving edges of the lungs than in inspiration. In pneumothorax of either of the pleural sacs the air compresses the lung, pushes the heart from its normal position, and the space which the air occupies in the pleura yields a clear hollow sound on percussion, whilst, by the ear or stethoscope applied to a corresponding part of the thoracic walls, we discover the absence of the respiratory murmur. ”

“ In the thorax, the diaphragm can descend, and the lungs can without danger occupy less space when there is considerable fat exhaled in the mediastinum. This remark, applicable also to the serum, explains an important phenomenon in diseases, viz. that a very small quantity of fluid poured out upon the tunica arachnoides can disturb the functions of the brain, whilst a great effusion is unattended with danger in the abdomen or the thorax. ”

“ Should the lungs be congested with blood, they must be emptied. This object may be attained either by pressing upon the lower part of the thorax, which will have the effect of forcing the blood out through the nostrils and mouth; or else the diaphragm separating the thoracic cavity from the abdomen may be cut through, and the extravasated blood can therefore be got out through the opening. The injection of the thoracic cavity can also be performed through the same opening. ”

“ Whenever the excitement, producing hydrothorax, is idiopathic and independent of an organic disease of the lungs, heart, &c. its remote causes may be either of a general or local kind; and are the same which produce, when applied in a higher degree, or under different states of the system, the other forms of inflammation. The effusion may take place in those cases in which, the individual being predisposed, the inflammation, owing to some peculiarity in the cause, does not reach beyond its lowest grade ”

“ PATHOLOGICAL ANATOMY.—In traumatic pneumothorax and simple cases, such as from the bursting of emphysematous alveoli, the presence of air is the only pathological product. If the pleura and adjoining organs are not diseased, the rupture or tearing cicatrizes rapidly, and the air disappears in a few days by absorption. If a quantity of air be admitted, the pneumothorax may last for months; yet if the pleura is healthy, the air itself will not produce local changes. If blood or morbid products flow in with the air, then inflammatory changes occur, and we have deleterious products effused. ”

“ If the air enters the pleura and takes the place of the pus, the chest remains enlarged. Indeed, it sometimes increases in size to such an extent as to cause suffocation unless the pus and gas are withdrawn. The valve made by the false membrane allowing the air to enter the cavity, but not to escape from it, causes the fluid to accumulate rapidly, and we have pneumothorax to a very painful degree. The diaphragm is pushed down, and, if the disease is on the right side, the liver is forced down, and descends to a level with the umbilicus. ”

“ Abnormal conditions of the pleuræ are frequent causes of cardiac displacements. In pneumothorax there is collapse of the lung on the affected side, and the elastic traction of the sound lung draws over the mediastinum and heart. It is not that the heart is pushed over, as so often stated, but the tension of the other lung, being unopposed, pulls the mediastinum toward the sound side. Later, when, as usually happens, effusion takes place, the pressure assists in the displacement. ”

“ It should always be remembered that the lung undergoes very various and opposite changes as the result of pressure on the bronchi, interrupting the entrance and egress of air from the lobules, and the physical signs of emphysema, infarction, congestion, or consolidation may exist in one or the other side. The ordinary methods of physical examination indicate the existence of pleural effusions, but large growths extending from the mediastinum or originating in the lung may so closely simulate such effusions that a positive diagnosis can be arrived at only by paracentesis. ”

“ Superficial Examination of Thorax.—Observe the position, color, and degree of distention of the lungs. It should be remembered that healthy lungs, as soon as the chest is opened, owing to their inherent elasticity, will collapse, and when this normal collapse is not seen it is generally due to a loss of elasticity as occurs in emphysema, to inflammatory diseases binding the lung to the chest wall, or to the alveoli being filled with solid or fluid substances or pent-up air. Most complete distention is seen when death is due to drowning or suffocation. ”

“ SYMPTOMS.—During the early stage of mitral insufficiency, when the hypertrophy of the right ventricle compensates for the regurgitation, there are no rational symptoms which would lead one to suspect its existence; but when the right ventricle is unable to overcome the obstruction to the pulmonary circulation caused by the regurgitant blood-current, there will be more or less dyspnoea, accompanied by a short, hacking cough, with an abundant expectoration of frothy serum. Sometimes the watery expectoration is blood-stained. ”

“ Traumatic pneumothorax may take place in consequence of an injury to the thoracic walls, of an exterior injury, or of a penetrating wound. The parts may be so bruised that pleural necrosis gives rise to sloughs and resulting openings. Fracture of ribs may tear the lungs, and allow air to enter the connective tissue and produce local emphysema. Violent contusions, as in a case recently observed by the author, produce laceration of the lung without the rib or costal pleura being injured. ”

“ As the diaphragm returns into the thorax during inspiration its progress will be accelerated by the weight of the descending intestines, and thus the recumbent posture may be sometimes useful in cases of bronchitis with emphysema, and so such cases may be seen sometimes lying down although there is considerable interference with the aëration of the blood. In cases of cardiac disease no benefit of this kind is obtained, and therefore we find that a large proportion of those whom we see sitting upright in bed in a hospital ward are suffering from disease of the heart. ”

“ Cancer of the lung or pleura may, by pressure, produce absorption and destruction of the walls of the blood-vessels, and cause discharge of their contents into the pleural cavity. Sir Thomas Watson253 reports a case where enormous hæmothorax caused enlargement of the left side, pushing the heart to the right of the sternum from caries of two ribs with ulceration through an intercostal artery. The blood never escapes from the lung into the pleura when there is considerable pulmonary apoplexy. ”

“ Though the lungs are closely applied to the costal sides at all times in the healthy state of these organs, still they slide freely within the thorax during the respiratory motions—forwards and backwards—over the serous pericardium, E, and upwards and downwards along the pleura costalis. The length of the adhesions which supervene upon pleuritis gives evidence of the extent of these motions. When the lung becomes in part solidified and impervious to the inspired air, the motions of the thoracic parietes opposite to the part are impeded. ”

“ William Hamilton, the author of a valuable treatise on the digitalis purpurea, thinks the hydrothorax a more frequent disease than has commonly been imagined, because he conceives that it has often been mistaken for organic disease of the heart. He names, with some precision, many symptoms of the latter complaint; but how remote he is from an accurate knowledge of it may be discovered by his opinion, that, in diseases of the heart, “the patient can lie down with ease, and seldom experiences much difficulty of breathing.” ”

“ But if no medication will have proved successful, the symptoms of stenosis, dyspnoea, cyanosis, and the supra- and intraclavicular and epigastric recension increase steadily to an alarming extent. When the pulse becomes frequent and intermitting, even without the presence of asphyxia and anæsthesia, air ought to be introduced into the lungs by tracheotomy. No positive rules can be laid down as to the length of time one ought to wait before performing it. No subdivision of the disease into several stages is of any benefit in selecting the exact period in which the trachea must or may be opened. ”

“ The same observation applies to all the hemorrhages; they require means wholly opposite, according as they are active or passive; a remark moreover that is applicable to all diseases that have increased exhalations or secretions, whatever may be their seat. It is not the phenomenon that we are to resist, but the cause that has produced it. We diminish the forces, when serum is accumulated in the thorax, from a pleurisy; we increase them, when it accumulates from a disease of the heart, the lungs, &c. ”

“ PATHOLOGICAL ANATOMY.—Hydrothorax being merely dropsy of the thoracic cavity, there is no lesion of the pleura. There is a collection varying from 100 grammes to many liters of fluid in the cavity. It differs from the effusion in subacute pleurisy in its small quantity of fibrin, in having far less of albuminoid material, and no white blood-corpuscles. The water collects almost always in both sides of the chest, more on the side on which the patient lies in bed. In the recumbent position the fluid gravitates posteriorly more than the effusions of pleurisy. ”