The humoral asthma is a disorder of the mucous glands of the lungs, in consequence of which they are relaxed, and the discharge of mucus, being unnaturally copious, obstructs the freedom of respiration. This kind of asthma is more constant; the convulsive more violent, and of shorter duration. The humoral asthma is more severe both with respect to the cough and difficulty of breathing in winter; but in summer, when the weather is warm, and perspiration free, it often disappears totally between the intervals of the fits of the convulsive asthma. The convulsive asthma, too, is sometimes severer in winter than in summer, especially when combined with the humoral, or with a catarrh. But it often happens that the warm weather affords little or no relief; nay, even in many cases it is observed, that the irritability of the constitution and the rarefaction of the blood are so much increased by the warmth of the weather, that the frequency and severity of the fits are greater in the warm and sultry, than in the cold seasons of the year. In this case the humoral asthma is continued on during the summer months by the convulsive asthma, as a symptom of the natural and critical solution of the fits. After the convulsive asthmas there is often a great soreness in the breast, partly from the violent muscular exertion, and partly from the frequency and severity of the cough. Sometimes, too, there are shooting pains in the sides, which are extremely painful and alarming to the patient; but the judicious practitioner will easily distinguish them from internal affections of the breast, by the external soreness, and the acuteness of the pain in consequence of motion. The frequent returns of fits sometimes cause obstructions in the.lungs, which, as the dissection of dead bodies clearly ascertains, appear full of knots or tubercles. These tubercles are most liable to occur in those who have naturally a narrow contracted chest, in which the lungs have not a free and easy motion; these render the disorder very obstinate, occasioning a long continuance of the cough after the asthmatic fit, frequently ending in small inflammations of the lungs, attended with internal pains, difficulty of breathing, and hectic fever. We have already observed, that the humoral asthma often supervenes on the convulsive. It is necessary also to observe, that the convulsive sometimes attacks those who have long been previously afflicted with the humoral asthma. Patients subject to catarrhs and winter coughs, during which they expectorate a considerable quantity of thick or frothy phlegm, are sometimes suddenly seized with violent difficulty of breathing, and great tightness over the breast, so as to dread even instant suffocation. This new complaint, after having tormented them for some hours, or perhaps a day or two, also leaves them suddenly, and they look back with surprise at their happy deliverance from so formidable and unexpected an enemy. Their old habitual cough and asthma, with soreness and stuffing in the breast, still remain; but they bear it without repining. In this manner they continue for some time, till the convulsive asthma returns, perhaps, with additional violence. Thus, the convulsive asthma becomes habitual to the patient, and he has the misfortune to find himself labouring under a complication of two diseases; the one aggravating the other, and both growing worse.

The convulsive asthma sometimes attacks persons of a thin spare habit, whose constitutions have been greatly emaciated by a long exposure to causes of general or chronic weakness. In some cases it seizes patients who are robust and full of blood, particularly if they have small vessels and strait chests. At other times it occurs in those who are gross, phlegmatic, corpulent, and in such habits it is often very distressing. In general, the indolent and luxurious suffer in a very considerable degree, and the disease seems to be conveyed to the children. It is frequently connected likewise with hysterical and hypochondriacal complaints, in irritable and relaxed constitutions. The convulsive asthma, recurring for many years, is capable of reducing the strongest constitutions, and of bringing on the symptoms of general debility; but if it attacks a constitution already weakened and exhausted, it is obvious that it will necessarily weaken and exhaust it more. The stomach and bowels are more particularly liable to be affected in the convulsive asthma; they are often seized with colic pains, distended with wind, tormented with burning heats, and agitated with tremulous motions, which give a sensation to the patient of something moving and fluttering within him. Floyer, too, has observed, that slight fits of the asthma often affect the stomach and bowels, not the lungs. The appetite is greatly impaired, sleep is often prevented, or it is disturbed and unrefreshing. The menses are sometimes obstructed, and sometimes they are brought on before the usual period; and when plethora prevails, that discharge is accompanied with relief. The patient is generally costive, though sometimes he will have loose stools. The extremities, particularly the arms, shoulders, and upper parts of the body, are often affected with great uneasiness. Symptoms of fever are not essential to the disease, though they frequently occur, especially when the humoral asthma or a catarrh is complicated with the convulsive. A hectic fever, with a colliquative diarrhoea, faintings, palpitations, violent vomitings, coldnessof the extremities, swelled legs, and other dropsical symptoms, arising from weakness, relaxation, and obstruction to the circulation of the blood through the lungs, is common in the last stage of the disease. Asthma may attack at any age, but its general approach is after the prime of life.

From the preceding account of the symptoms of the convulsive asthma, it will appear obvious that the distinction of it from every other disease cannot be difficult. The sudden attack of the fits, the short time of their duration, the violence of their symptoms, the state of case and good health between them and their returning at intervals, will sufficiently characterise the complaint. The convulsive asthma is sometimes combined with the humoral asthma, pleurisy, peripneumony, dropsy of the breast, catarrhal and consumptive disorders; but the distinctions will require an accurate study of the respective histories of the different complaints which bear any resemblance to it. In many instances in the practice of medicine, words can never convey those minute distinction:, which are very obvious to the eye and other senses.