From communications, with which I have been favoured from Dr. Pearson, who has occasionally reported to me the result of his private practice with the vaccine virus in London, and from Dr. Woodville, who also has favoured me with an account of his more extensive inoculation with the same virus at the Smallpox Hospital, it appears that many of their patients have been affected with eruptions, and that these eruptions have maturated in a manner very similar to the variolous. The matter they made use of was taken in the first instance from a cow belonging to one of the great milk farms in London. Having never seen maturated pustules produced either in my own practice among those who were casually infected by cows, or those to whom the disease had been communicated by inoculation, I was desirous of seeing the effect of the matter generated in London, on subjects living in the country. A thread imbrued in some of this matter was sent to me, and with it two children were inoculated, whose cases I shall transcribe from my notes. Stephen Jenner, three years and a half old. 3d day: The arm shewed a proper and decisive inflammation. 6th: A vesicle arising. 7th: The pustule of a cherry colour. 8th: Increasing in elevation. A few spots now appear on each arm near the insertion of the inferior tendons of the biceps muscles. They are very small and of a vivid red colour. The pulse natural; tongue of its natural hue; no loss of appetite or any symptom of indisposition. 9th: The inoculated pustule on the arm this evening began to inflame, and gave the child uneasiness; he cried and pointed to the seat of it, and was immediately afterwards affected with febrile symptoms. At the expiration of two hours after the seizure a plaster of ung. hydrarg. fort, was applied, and its effect was very quickly perceptible, for in ten minutes he resumed his usual looks and playfulness. On examining the arm about three hours after the application of the plaster its effects in subduing the inflammation were very manifest. 10th: The spots on the arms have disappeared, but there are three visible in the face. 11th: Two spots on the face are gone; the other barely perceptible. 13th: The pustule delineated in the second plate in the Treatise on the Variolae Vaccinae is a correct representation of that on the child's arm as it appears at this time. 14th: Two fresh spots appear on the face. The pustule on the arm nearly converted into a scab. As long as any fluid remained in it it was limpid. James Hill, four years old, was inoculated on the same day, and with part of the same matter which infected Stephen Jenner. It did not appear to have taken effect till the fifth day. 7th: A perceptible vesicle: this evening the patient became a little chilly; no pain or tumour discoverable in the axilla. 8th: Perfectly well. 9th: The same.