Mr. Cline, who in July last was so obliging at my request as to try the efficacy of the cow-pox virus, was kind enough to give me a letter on the result of it, from which the following is an extract: 

“My dear sir: 

“The cow-pox experiment has succeeded admirably.  The child sickened on the seventh day, and the fever, which was moderate, subsided on the eleventh.  The inflammation arising from the insertion of the virus extended to about four inches in diameter, and then gradually subsided, without having been attended with pain or other inconvenience.  There were no eruptions.

“I have since inoculated him with smallpox matter in three places, which were slightly inflamed on the third day, and then subsided.

“Dr. Lister, who was formerly physician to the Smallpox Hospital, attended the child with me, and he is convinced that it is not possible to give him the smallpox.  I think the substituting the cow-pox poison for the smallpox promises to be one of the greatest improvements that has ever been made in medicine; and the more I think on the subject, the more I am impressed with its importance.

“With great esteem

“I am, etc., “Henry Cline.

“Lincoln’s Inn Fields, August 2, 1798.”

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.