frequency of the pulse, which occurs twice every day to persons in health, and may be produced by acrimony alone. These exacerbations, indeed, do not happen without the proper circumstances of pyrexia; but the spasm of the extreme vessels in a hectic does not seem to be so considerable as in other fevers; and hence the state of sweat and urine which appears so early and so constantly in hectics. Upon the same supposition of an acrimony corrupting the fluids, and debilitating the moving powers, I think that most of the other symptoms may also be explained.

863. Having thus considered the characteristical symptoms and chief part of the proximate cause of phthisis pulmonalis, I proceed to observe, that an ulcer of the lungs, and its concomitant circumstance of hectic fever, may arise from different previous affections of the lungs; all of which however may, in my opinion, be referred to five heads; that is, 1, To an hæmoptysis; 2, To a suppuration of the lungs in consequence of pneumonia; 3, To catarrh; 4, To asthma; or, 5, To a tubercle. These several affections, as causes of ulcers, shall now be considered in the order mentioned.

864. It has been commonly supposed, that an hæmoptysis was naturally, and almost necessarily, followed by an ulcer of the lungs: but I will presume to say, that, in general, this is a mistake; for

there have been many instances of hæmoptysis occasioned by external violence, without being followed by any ulcer of the lungs; and there have also been many instances of hæmoptysis from an internal cause without any consequent ulceration. And this too has been the case, not only when the hæmoptysis happened to young persons, and recurred for several times, but when it has often recurred during the course of a long life. It is indeed easy to conceive, that a rupture of the vessels of the lungs, like that of the vessels of the nose, may be often healed, as the surgeons speak, by the first intention. It is probable, therefore, that it is an hæmoptysis in particular circumstances only, which is necessarily followed by an ulcer; but what these circumstances are, it is difficult to determine. It is possible, that merely the degree of rupture, or frequently repeated rupture preventing the wound from healing by the first intention, may occasion an ulcer; or it is possible that red blood effused, and not brought up entirely by coughing, may, by stagnating in the bronchiæ, become acrid, and erode the parts. These however are but suppositions, not supported by any clear evidence. And, if we consider, that those cases of hæmoptysis which follow the predisposition, (832, 835) are those especially which end in phthisis, we shall be led to suspect, that there are some other circumstances which concur here to determine the consequence of hæmoptysis, as I shall hereafter endeavour to shew.

865. Any supposition, however, which we can make with respect to the innocence of an hæmoptysis, must not supersede the measures proposed above for its cure; both because we cannot certainly foresee what may be the consequences of such an accident, and because the measures above suggested are safe; for, upon every supposition, it is a diathesis phlogistica that may urge on every bad consequence to be apprehended.

866. The second cause of an ulceration of the lungs to be considered, is a suppuration formed in consequence of pneumonia,

867. From the symptoms mentioned in 858, 859, it may with reason be concluded, that an abscess, or, as it is called, a vomica, is formed in some part of the pleura, and most frequently in that portion of it investing the lungs. Here purulent matter frequently remains for some time, as if inclosed in a cyst: but commonly it is not long before it comes to be either absorbed and transferred to some other part of the body; or that it breaks through into the cavity of the lungs, or into that of the thorax. In the latter case, it produces the disease called empyema; but it is only when the matter is poured into the cavity of the bronchiæ, that it properly constitutes the phthisis pul, monalis. In the case of empyema, the chief circumstances of a phthisis are indeed also present;

but I shall here consider that case only, in which the abscess of the lungs gives occasion to a purulent expectoration.

868. An abscess of the lungs, in consequence of pneumonia, is not always followed by a phthisis: for sometimes a hectic fever is not formed; the matter poured into the bronchiæ is a proper and benign pus, which is frequently coughed up very readily, and spit out: and, though this purulent expectoration should continue for some time, yet, if a hectic does not come on, the ulcer soon heals, and every morbid symptom disappears. This has happened so frequently, that we may conclude, that neither the access of the air, nor the constant motion of the lungs, will prevent an ulcer of these parts from healing, if the matter of it be well-conditioned. An abscess of the lungs, therefore, does not necessarily produce the phthisis pulmonalis ; and if it be followed by such a disease, it must be in consequence of particular circumstances which corrupt the purulent matter produced, render it unsuitable to the healing of the ulcer, and at the same time make it afford an acrimony, which, being absorbed, produces a hectic and its consequences.

869. The corruption of the matter of such abscesses may be owing to several causes; as, 1, That the matter effused during the inflammation, had not been a pure serum fit to be converted into

a laudable pus, but had been united with other matters which prevented that, and gave a considerable acrimony to the whole: or, 2, That the matter effused, and converted into pus, either merely by a long stagnation in a vomica, or by its connection with an empyema, had been so corrupted, as to become unfit for the purpose of pus in the healing of the ulcer. These seem to be possible causes of the corruption of matter in abscesses, so as to make it the occasion of a phthisis in persons otherwise sound; but it is probable, that a pneumonic abscess does especially produce phthisis when it happens to persons previously disposed to that disease, and therefore only as it concurs with some other causes of it.

870. The third cause supposed to produce phthisis, is a catarrh; which, in many cases, seems, in length of time, to have the expectoration of mucus proper to it, gradually changed into an expectoration of pus; and at the same time, by the addition of a hectic fever, the disease, which was at first a pure catarrh, is converted into a phthisis. This supposition, however, is not easily to be admitted. The catarrh is properly an affection of the mucous glands of the trachea and bronchiæ, analogous to the coryza, and less violent kinds of cynanche tonsillaris, which very seldom terminate in suppuration. And although a catarrh should be disposed to such termination, yet the ulcer pro