Your letter of the 14th. inst, enclosing one of the 25th. ulto. came duly to hand.

I was struck with the expediency of establishing a popular criterion as to the precise time of taking the matter, and I entirely coincide with you in opinion that it should be fixed on Eight times twenty four hours, this being the result of my own observation during the last season. I know that it differs somewhat in different subjects, but in the formation of a general rule it is necessary to impose a limitation. Jenner says “I prefer the 5th. 6th. 7th. 8th. and (if the efflorescence is not far advanced beyond the margin of the pustule the 9th.”—But I conceive this is impossible to be discovered with requisite precision on the skin of the african? Mr. Aikin is not a good guide on this subject. His publication was not the result of his own experience; nor do I believe that Dr Aikin, his very learned & classical father, had any experience with the disease.

As to the criterion of limpid matter, I know it to be fallacious; for in the rising of a vesicle, or blister from any cause, the scarf-skin seperates from the true, and a portion of the superfluous water of the blood, & sometimes of the coaguable lymph is found under it; and I have known this limpid fluid exude from the vaccine pustule, especially after being too much exhausted and irritated in procuring virus. This exudation gives a shining glazy appearance to the thread. I know of no writer, or practitioner who has made this distinction.—

I am glad to find that other physicians are following the lead of Dr. Cox in Philadelphia. I have heretofore been surprized at the fastidious style of some of the fathers in the art in that city.—I have never heard anything respecting Dr. Gantt’s progress in the business. I have written to him several times, but never had an answer.

I have been made uneasy at one occurrence. In an unrestrained & perfectly confidential correspondence with my intimate friend Dr. Lettsom, I transmitted him a copy of your first letter to me dated Decr. 25th. 1801. acknowledging the receipt of my pamphlet &c Altho I did this in the pride of my heart, I meant that he and Jenner only should partake of my satisfaction; but my friend Lettsom printed it in his volume on the cow-pox; and the Editors of a new edition of Aikin’s little book just published at Philadelphia have prefixed it to that work. Anti-monarchical as I am, I nevertheless think that a strong line of distinction should always be drawn between the private citizen & the Chief Magistrate of a nation, towards whom I am disposed to say in the language and meaning of that old book which all we New England folks sware by, “YE ARE GODS!”

My friend Lettsom has taken one method to check my inclination of spreading abroad his useful & philanthropic volume. My venerable kinsman Dr. Fothergill used to say, “a man’s conduct should be his picture.” Accept the sentiments of profound respect.