A large pericardial effusion is some times difficult to distinguish from left sided pleural effusion. The position of the cardiac impulse is the most impor tant guide; it is not displaced to the right in pericardial effusion. The heart is feeble and the impulse weak and may be diffuse.
In pleurisy the impulse is commonly easily felt unless it is behind the ster num and the heart-sounds are strong. In large pericardial effusion there is marked dyspncea and a peculiar cyanotic hue of the general surface. In the left axilla the percussion-note is Skodaic un less obscured by associated pleural ef fusion. In the latter case removal of the pleural effusion is not followed by due re lief and the cardiac impulse is not af fected.
On the right side subphrenic abscess or hydatid cyst of the liver may force the diaphragm high in the thorax and be mistaken for pleural effusion. The upper limit of dullness is usually arched and in some cases a friction-rub is pres ent over all parts of the tumor: a sign that should arouse suspicion. Then there is fullness and a feeling of tension in the hypochondrium; the liver is some times depressed, but it may be in pleural exudations also. On introducing a can nula the pus is forced out during inspi ration in subphrenic abscess, in pleural effusion during expiration.
Hydrothorax presents all the signs of pleural effusion, and intrathoracic tumors may simulate and often give rise to it.
As to the nature of the effusion, if the si,ipas leave us in doubt the use of the aspirator usually decides with certainty. Hectic fever, sweats, oedema of the chest, bulging of the intercostal spaces, prom inence of the veins of the chest, and leu cocytosis indicate the presence of pus. Sero-fibrinous effusion, however, may be attended by protracted fever, with gen eral prostration. On the other hand, purulent effusion may exist without def inite symptoms.
The "De Musset" sign in pleurisy, a rhythmical antero-posterior nodding of the head, synchronous with the radial pulse, thought to be pathognomonic of aortic disease, noted in a case of left pleurisy with large effusion. The degree of effusion seems to play an important ride in the production of this physical sign. M. H. Frenkel (Presse Med., Nov.
14, 1900).
\s to whether the effusion is tubercu lar or infectious, when one-half or more of the liquid consists of lymphocytes it is probably tubercular. A tubercular effusion also shows polynuclear ]euco cytes at first—sometimes with bacilli which cannot be cultivated. Lympho cytosis occurs gradually. Punctures should be made once a week and the exudate examined. Lymphocytes must be distinguished from degenerated poly nuclear forms and pseudolymphocytes. Epithelial cells, while rarely seen, may have degenerated so that they resemble Ehrlich's large mononuclear cells. Widal, however, considers these mononuclear leucocytes, since they have frequently been found in pleural effusions. In acute, infectious pleurisy polynuclear and epithelial cells are in the majority. A. Wolff (Berliner klin. Wochen., Feb. 10, 1902).
Etiology.—Pleurisy occurs at all ages, even in the infant of a week or two, as well as in the aged. Sero-fibrinous pleu risy is probably most common between the ages of twenty and forty, while em pyema is more frequently met with in children under ten years of age. Males, especially in the middle period of life, suffer much oftener than females.
Chill from exposure to cold and wet is often the exciting cause of pleurisy. It probably acts here, as well as in other dis eases, by lowering vitality through dis turbance of nutrition, thus rendering the pleura more susceptible to the agent ex citing the inflammation.
A weakly constitution and previous ill health have a marked effect in lowering the powers of resistance to the influences that produces disease. This is especially evident in the liability to pleurisy among those who have a tendency to pulmonary tuberculosis.
Pleurisy often results from extension of inflammation from neighboring dis eased organs, especially from the lungs; also from the pericardium and medias tinum. It may follow also injury of the chest-wall and lungs. It may also occur in the course of acute or chronic dis eases, such as septiewmia, the acute fevers, acute rheumatism, Bright's dis ease, hepatic cirrhosis, and malignant disease.