(From or spiro, or rather anhelo, to breathe short). This is an impeded and very laborious respiration, joined with inexpressible anxiety and straitness of the precordia, preventing a free circulation of blood through the lungs, arising from various causes, and threatening suffocation. The characteristic symptom of this disease is a chronical, and sometimes a periodical, difficulty of breathing; hence it differs from orthopnoea, which is acute; from dyspnoea, because that is continued.

This disease has generally been considered to be of two kinds; the humoral, pituitous, or moist; the spasmodic, dry, nervous, or convulsive. Both which are properly included in the subsequent definition. ' A difficulty of breathing, coming on at intervals, with a sense of straitness in the breast, and sibilating respiration; at the beginning of the paroxysm, attended with an uneasy cough, or no cough at all; towards the conclusion, a free cough, often attended with a copious expectoration of mucus. Dr. Cullen ranks this genus of disease in the class Neuroses, and order Spasmi, dividing it into three species.

1st. Asthma spontaneum; to which belong the orthopnaea spasmodica, and hysterica, when there is no manifest cause, or any other disease attending.

2d. Asthma exanthematicum, when it arises from the retropulsion of some acrid humours from the surface of the body.

3d. Asthma plethoricum, when it is the consequence of some accustomed sanguinary evacuation suppressed, or a spontaneous plethora. - The hypochondriac, arthritic, and venereal species, are symptomatic only.

The attack of the convulsive asthma is sudden, and at its first appearance the fit is short. The symptoms which usually precede it are languor, flatulency, head-ach, sickness, pale urine, disturbed sleep, a sense of straitness and fulness about the pit of the stomach. In some cases there is an uncommon stupor, drowsiness, and heaviness. The fit is frequently observed to come on about one or two oclock in the morning, or at any hour after the first sleep. The patient wakes suddenly, and feels a great tightness and constriction around the chest, with a difficulty of breathing, and an impediment to the free admission of air into the lungs. Both inspiration and expiration are slow, laborious, and accompanied with constant wheezing, particularly the latter. Great bodily anxiety always attends this disorder. As the lungs cannot be sufficiently dilated with air, the passage of the blood through the pulmonary vessels is not free. Hence the face, in full and plethoric habits, appears red and bloated, and the vessels of the eyes are unnaturally turgid. The action of the heart is greatly disturbed, as is evident by the weakness, irregularity, and increased quickness of the pulse. Dur-d d 2 ing the fit, the patient has generally a longing instinctive desire for cool fresh air, which always revives him. A small close room, with a lire in it, is extremely offensive, and all warm things, given internally, increase the flatulency in the stomach and bowels, which is always the most troublesome after a full meal. When the fit has continued a few minutes, half an hour, or an hour, it leaves the patient;his respiration becomes free and natural, his pulse slow and regular, his complexion puts on its usual appearance, and the bodily anxiety goes off. The urine is generally pale, and the skin somewhat dry before the fit, and during its progress; but at the termination of it, the urine for a clay or two is high coloured, and deposits a sediment, and the skin feels soft and moist. This is the description of a first and moderate attack of the disorder. In some cases it appears in a more violent form, even at its commencement, and continues for several days before the lit terminates. Sometimes the patient will have one fit, and then remain free for many months. At other times fits come on for several nights together, the patient appearing almost perfectly well during the day, with his appetite and pulse natural. When the asthma once attacks, it seldom or never fails to recur, though the intervals between the fits are very uncertain; when rooted in the constitution, it often makes its attack in the spring and autumn. In many cases it attacks periodically once in ten days or a fortnight. Sometimes it occurs regularly at the full and change of the moon. Floyer mentions a case where the fits occurred for seven weeks together, and the patient was obliged to sleep in a chair; and from the strictest observations it is found, that there is no certainty nor regularity observable in the attacks of the asthma. The reason why the fits so often occur first in the night, is thought to be owing to the heat of the bed, and the horizontal posture in which the patient lies.

Relapses are commonly attended with an increase of the symptoms, and the vigour of the constitution is gradually impaired, till, by length of time, general or chronic weakness is induced. The difficulty of breathing in the fit arises to a much higher degree in these relapses, and the sensation of tightness over the breast is so great and distressing, that the patient feels as if he were bound with cords. His anxiety at this period is inexpressible, an,d he labours in respiration as if every moment would be his last. Severe vomiting frequently occurs, and the matter discharged is slimy and frothy, or of a greenish or yellow colour. The hands and feet are cold, and the patient is subject to palpitations and faintings. Cool fresh air becomes absolutely necessary. The eyes are prominent, the face is sometimes pale and sometimes high coloured, bloated, or livid; the pulse extremely weak, irregular, and even intermitting; there is a difficulty of swallowing,' the patient can scarcely speak, cough, or expectorate during the fit, and the stomach and bowels are violently distended with wind. While thus labouring for breath, he is obliged to rise from his bed, he cannot bear even the weight of the bed clothes upon him. His shoulders are constantly elevated, to give the muscles of the chest their greatest power of action in raising the ribs in inspiration. At this time, too, the patient, though before costive, will frequently have a loose stood. When the violence of the fit abates, and respiration becomes free, the cough returns, and the patient begins to expectorate, phlegm, which is sometimes intermixed with blood. As soon as an easy copious expectoration takes place, it affords great relief, for the evacuation is made immediately from the parts affected, from the vessels which have been obstructed. This expectoration is one of the most certain signs of the abatement of the complaint, as it denotes the solution of the contraction of the bronchial air vessels; particularly if a moisture and softness of the skin, and a sediment in the urine, make their appearance. The blood which is spit up in this complaint proceeds generally from a rupture or dilatation of blood vessels in the lungs. In some cases, indeed, the quantity of blood which is spit up is in full habits very considerable, and at the same time accompanied with an abatement of the symptoms. But all free discharges of blood from the lungs, though they afford relief, are unfavourable signs, as they denote greater violence of the disease; during the course of which, the very efforts of nature to relieve are in themselves so alarming. The nose, too, will sometimes gush out with blood during the severity of the fit, from the obstruction given to the return of the blood through the pulmonary vessels into the left auricle of the heart. Thus in a short time the fit of the convulsive asthma goes off. In a course of years one fit succeeds another, and the disorder increases in the violence and duration of the fits, as well as in the frequency of their returns. The expectoration from the mucous glands of the lungs, which still continues to relieve at the termination of the fits, becomes itself a very troublesome symptom. These glands are relaxed, and the discharge of mucus greater than natural. Hence the bronchial or air vessels are frequently obstructed with phlegm, and from this cause the freedom of respiration is disturbed: the patient breathes with unusual difficulty, although -his convulsive fits be absent. When he first wakes in the morning he has generally a severe fit of coughing, which continues till he has discharged the phlegm that provoked the cough, by preventing the free admission of air into the air vessels. Through the day, at different times, the cough still recurs, but with less violence; and in the evening it is often very teasing and distressing, especially on any sudden motion of the body, or in cold, damp, foggy weather, which obstructs the exhalation of the perspirable matter from the lungs. Thus the humoral asthma is united with the convulsive, and both together exist in the same patient.