3. I mentioned, formerly, that Doctor Martin was often unsuccessful in the application of his powder. This was occasioned by his using it indiscriminately in _all_ cases. In schirrous and cancerous tumours, the knife should always be preferred to the caustic. In cancerous ulcers attended with a scrophulous or a bad habit of body, such particularly as have their seat in the neck, in the breasts of females, and in the axillary glands, it can only protract the patient's misery. Most of the cancerous sores cured by Doctor Martin were seated on the nose, or cheeks, or upon the surface or extremities of the body. It remains yet to discover a cure for cancers that taint the fluids, or infect the whole lymphatic system. This cure I apprehend must be sought for in diet, or in the long use of some internal medicine. To pronounce a disease incurable, is often to render it so. The intermitting fever, if left to itself, would probably prove frequently, and perhaps more speedily fatal than cancers. And as cancerous tumours and sores are often neglected, or treated improperly by injudicious people, from an apprehension that they are incurable (to which the frequent advice of physicians "to let them alone," has no doubt contributed), perhaps the introduction of arsenic into regular practice as a remedy for cancers, may invite to a more early application to physicians, and thereby prevent the deplorable cases that have been mentioned, which are often rendered so by delay or unskilful management. 4. It is not in cancerous sores only that Doctor Martin's powder has been found to do service. In sores of all kinds, and from a variety of causes, where they have been attended with fungous flesh or callous edges, I have used the doctor's powder with advantage. I flatter myself that I shall be excused in giving this detail of a _quack_ medicine, when we reflect that it was from the inventions and temerity of quacks, that physicians have derived some of their most active and most useful medicines. OBSERVATIONS UPON _THE TETANUS_. For a history of the different names and symptoms of this disease, I beg leave to refer the reader to practical books, particularly to Doctor Cullen's First Lines. My only design in this inquiry, is to deliver such a theory of the disease, as may lead to a new and successful use of old and common remedies for it. All the remote and predisposing causes of the tetanus act by inducing preternatural debility, and irritability in the muscular parts of the body. In many cases, the remote causes act alone, but they more frequently require the co-operation of an exciting cause. I shall briefly enumerate, without discriminating them, or pointing out when they act singly, or when in conjunction with each other.