a. Of the nervous irritations in which they may be usefully employed we have examples in internal neuralgia, and spasm of internal organs, as of the stomach, bowels, gall-ducts, bronchial tubes, and larynx; and in disordered internal functions of almost every kind, dependent on an excitant cause. Special diseases in which this indication may exist are gastrodynia, simple spasm of the stomach, obstinate vomiting, enteralgia, colic in its different forms, the gastrointestinal spasms of cholera, asthma, pure spasmodic croup, angina pectoris, internal forms of nervous gout and rheumatism, obstinate cephalalgia, and all the diversified disorders of spinal irritation, in which the application must be made over the seat of tenderness in the spinal column.

In the course of acute diseases, particularly those of a febrile character, great nervous disorder often supervenes, with restlessness, jactitation, universal uneasiness, mental discomposure, want of sleep, etc. These may frequently be most happily quieted by a pair of blisters to the arms or legs, which probably operate by concentrating the nervous irritation in the seat of their application, and thus relieving it elsewhere. Under these circumstances, it is no uncommon event for a patient, suffering under obstinate wakefulness, to fall asleep while the blisters are drawing, and to sleep soundly through the whole night.

b. Of the use of blisters in internal vascular irritations, we have examples in active congestive affections of the brain, lungs, and abdominal viscera. Gout and rheumatism often assume these forms. The different hemorrhages are other examples. The seat of the blister is often an important consideration in these affections. When the congestion depends exclusively upon a local cause of irritation, or is, to a considerable degree, fixed and constant in the part, it may be best to apply the blister near the seat of the disorder; as to the back of the neck in cerebral congestion and epistaxis, over the lungs in haemoptysis, over the stomach in haematemesis, and over the liver in colic, caused by hepatic disorder. But, where the affection is dependent on a constitutional cause, as of gout or rheumatism, or repelled cutaneous eruption, the blister should be applied either to the legs or forearms, or to that part of the surface near which the disease may have been seated before retrocession or repulsion. Again, when the affection con-rather in a determination of blood, which may be diverted elsewhere, than in a fixed vascular irritation in the part, the blister should be applied as remotely as possible from the place to which the morbid excitement may be directed. if applied near this part, it will add to the general current of blood in that direction, and might even aggravate the disease. if applied to the extremities, so as to draw the blood and nervous energy to the remotest part of the body, it must lessen the amount proceeding towards the seat of the affection, and does so often in a sufficient degree to effect a cure. Thus, in frequently recurring attacks of cerebral congestion, of epistaxis, of haemoptysis, etc., in which the symptoms depend rather on some cause occasionally sending excitement into the part, than on disease positively fixed in it, cures may sometimes be effected by blisters to the extremities, which would not happen were the revulsive agent applied near the part affected. The most obstinate case of epistaxis that I have witnessed, which, though frequently arrested, would as often return, and even threatened serious consequences, was in a pregnant woman, and yielded promptly to energetic revulsive applications to the legs, below the knee.

c. In internal and subcutaneous inflammations, blisters are of very great importance, and are, indeed, among the standard remedies. These affections are so firmly seated, that revulsive impressions at a distance, though useful, are not sufficiently powerful to exert a strong influence upon them. To be effective, the blisters must, in these cases, be applied as near the seat of the disease as possible-upon the surface immediately over it whenever practicable. Thus, in inflammation of the cerebral lobes, it should be applied to the scalp; of the base of the brain, to the back of the neck; of the lungs, or pleura, to the chest; of the stomach, to the epigastrium, etc.

Another most important consideration, in relation to the use of blisters in internal inflammations, is the period of the disease at which they ought to be employed. No therapeutic point is better settled than the impropriety of using blisters, in the highest stage of general and local excitement, in acute inflammation. in this condition, they almost always fail to remove the inflammation, while they add their own general excitation to the existing fever, and thus augment the constitutional disturbance, which reacts again injuriously on the local affection. The period for their application is after the subsidence or reduction both of the local and general excitement, when, though the disease is fixed, the blood is less irritant in its character, and its movement through the disordered part less impetuous. A blister at this period will often most happily subdue the residue of an inflammation, which might otherwise advance to suppuration or gangrene, or subside gradually into the chronic form. it should always be preceded by such an amount of depletion, general and local, and of other sedative influence, as the case may seem to call for. As a general rule, the fifth day of an acute inflammation is about the proper period for applying the blister, though certain circumstances may call for an earlier application, or require a longer postponement. Thus, in typhoid inflammations, it may be applied at a much earlier period; and in other cases of great violence and danger, it may be proper to concentrate all the remedies within a shorter time, and thus prepare for an earlier application of the blister by a very energetic use of depletory measures. in chronic inflammations, they may be employed at all stages, and are often very highly useful. in such cases, however, they must, in many instances, be frequently repeated, to be successful. in chronic inflammation of the great joints, particularly of a rheumatic character, they are a most efficient remedy, when frequently repeated; though a single application will be of little use.

4. A third principle upon which blisters act is that of substitution or supersession; removing the disease by establishing their own action in the part affected, through a more potent influence than that of the morbid cause. in this way may be explained their operation in obstinate cutaneous eruptions, and possibly in erysipelas.

5. The local stimulation they produce is useful in some cases of anaesthesia of the surface and subcutaneous tissue, local muscular paralysis, and threatened gangrene.

6. Blisters also deplete, and, when kept open by stimulating dressings, sometimes do so very considerably, so as to produce a strong local, if not constitutional impression. They are thus useful in inflammation, especially when somewhat superficially situated, as in the sub-cutaneous cellular tissue, the external absorbent glands, and the arteries, veins, and nervous trunks of the extremities. in these cases, they act doubly, by revulsion and depletion. Seeming neuralgia is not unfrequently traceable to some tender spot in the course of the nervous trunk supplying the part affected; and a blister over this tender spot will often prove highly serviceable.

Upon this principle also, blisters have been recommended in dropsy; and sometimes they very rapidly drain off the effused serum. But they are a hazardous remedy, especially if applied to the extremities in a very distended state; as they are apt to induce sloughing, in consequence of the feeble vitality of the part. I have seen an instance of terrible gangrenous ulcers in the extremities, in a case of obstinate dropsy, in which the whole of the effusion was removed, though the patient died exhausted. if ever employed in these cases, they should be applied to the chest and abdomen, and then, not merely to fulfil this indication, but when they may be called for also to relieve some internal inflammation.

7. The pain of blisters is sometimes useful in hypochondriacal affections, and in the relief of other nervous disorder. A medical gentleman once assured me that, while a student, he was excessively troubled by apparently causeless depression of spirits, and that he never was so free from this trouble as when he had a small blister drawing in his epigastrium.

8. Still another purpose for which blisters may be used, is to obtain a denuded surface, for the endermic application of medicines.