Independently of the general ill consequence of improper management of the patient, the chief reason of the extraordinary fatality of this complaint among the negroes, appears to be the thickness of the skin, which resisting the effort of nature to protrude the morbid matter to the surface, tends to throw it back into the circulation. A proprietor of slaves, who was rather anxious for the conservation of his property, than scrupulous in his attachment to religious prejudice, desired me to inoculate five of them. A strong dose of senna was administered as preparative, and they were afterwards restrained as to diet. Three of them had not in the whole forty pustules, and soon recovered. The other two suffered much; and the eruption, though not confluent, proved fatal to one of them. Whether he had caught it before, been improperly treated, or whether it was the effect of habit of body, was not clear. These were of the true negro cast, called, _Fertît_. They were all under twelve years of age. _Guinea Worm._ The Mohammedans of Fûr, and the Arabs, call the idolaters in their neighbourhood _Fertît_, (فرتيت à فرت _improbus fuit_). The disease called the Guinea Worm is known among them by the same name. It is extremely common, and very troublesome to the slaves, and sometimes to free persons. It is by some esteemed contagious, which however is rather surmised than certified. It consists of a whitish tumour, at first hard and painful. Often shews itself about the knee, in the fleshy part of the thigh, and in the foot, just below the instep. As it is matured, a small white worm appears, which is to be wound off by degrees, and in coming out is followed by the discharge of purulent matter. If broken in the extraction, it is sometimes very inconvenient, and often lasts four or even six months. There is no certain cure for this disease, which most frequently shews itself in the beginning of winter, after the rains; but generally disappears at the commencement of the hot season. It seems to originate in the water, which is replete with animalcules, and which no care is used to purify. They find by the termination of the tumour the extremity of the worm, which they call _wullad-el-Fertît_, and in that spot, puncture the skin with a red-hot iron, which they conceive forces it out; but which always appeared to me a painful operation, without any kind of effect. There is observed in some individuals a greater disposition to this disease than in others, but it is not confined to age, sex, or colour. _Scrophula._