WHOOPING-COUGH, or pertussis, is an infectious disorder in which catarrh of the air-passages is combined with nervous, symptoms which may assume very serious proportions. The affection occurs in epidemics and may at tack the youngest infants : indeed, sometimes it appears immediately after birth. In such young children whooping-cough, even when not of a grave type, may cause serious consequences. It is principally dangerous, how ever, through its complications. These are numerous, and often appear towards the end of the disease, when the patient's strength is reduced by the length and severity of his illness.
Causation.—The disease usually occurs in epidemics, and appears to be eminently infectious. The channel of infection is the breath and expecto ration ; and the virus is capable of being conveyed by the atmosphere or even by the clothes. Children of all ages are very susceptible to the infec tious principle. The disease is excessively common under two years of age, very common, even, during the first twelve months. Unfortunately, I have kept no systematic record of the many cases of whooping-cough which have passed under my notice, but in eighty-nine cases of which I have preserved notes no less than twenty-four occurred in infants during the first year of life. Even this proportion probably represents imperfectly the frequency of the disease in young babies ; for in such subjects the spasmodic stage is often absent. Dr. R. J. Lee is of opinion that infants suffer from pertussis much more frequently than is supposed, and asserts that in a very young child a whoop ought rather to excite surprise than to be looked upon as an ordinary symptom. This is, perhaps, an extreme statement, but there is no doubt that in infants the disease frequently as sumes the form of an obstinate pulmonary catarrh with but little laryngeal spasm. After the tenth year the disease becomes very rare ; but it may be seen at any time of life; even, as is well known, quite at the close of ex treme old age.
Whooping-cough seems to be more common in the spring and autumn than in the other seasons of the year, and the epidemic is often found to precede or to follow quickly upon an epidemic of measles. A patient who has passed through one attack of whooping-cough is in little danger of his illness being repeated, for a second• attack in the same subject is rare. The infection, however, lasts for a considerable time after the whoop has ceased to be heard. Dr. Squire is of opinion that at least six weeks should be allowed to elapse before the patient can be trusted to associate with healthy children.
Pathology.—Examination of the body in a fatal case of pertussis reveals nothing to account for the special nervous symptoms which impart its most characteristic feature to the disease. We find signs of catarrh of the air passages, viz., congestion with hypersecretion of the mucous membrane within the glottis, of the trachea, and of the bronchi and their ramifica tions. We also find certain consequences produced by violence of cough and spasm, viz., pulmonary collapse and emphysema. In addition, we usually meet with some other morbid changes due to the complication by means of which the fatal issue has been brought about. Thus, there may be serious congestion and even extravasation of blood into or upon the brain, and sometimes signs of thrombosis of the intracranial sinuses, shown by colourless clots of laminated structure adhering to the walls. The lungs may be the seat of catarrhal pneumonia, and occasionally small extravasations are seen here as in the brain. Moreover, there is almost in variably enlargement of the bronchial glands, and the under surface of the tongue may be ulcerated more or less extensively.
No satisfactory explanation has yet been given of the real nature of the complaint. That the disease is due to inflammation of the pneumogastric nerve has been shown to be erroneous. Pressure upon the same nerve by enlarged glands may be rejected for the same reasons which render this explanation of the phenomena of laryngismus stridulus an insufficient one. In some respects the affection resembles a zymotic disease ; in others a neurosis. Some writers consider the complaint a purely catarrhal one ; others lay most stress upon the nervous symptoms. That the disease is something more than a mere catarrh is shown by the infectious nature of the secretion thrown off by the mucous membrane. In 1870 Letzerich believed he had discovered a species of fungus in the sputum, and sup posed that this was the morbid material which, carried from one person to another, settled upon the mucous membrane of the air-passages, and by its irritation gave rise to the spasmodic symptoms. Other observers, however, have not confirmed this alleged discovery. More lately Dr. Carl Burger, of Bonn, has described a bacillus which he has found in the expectoration of children suffering from whooping-cough, and states that it is peculiar to this complaint.