Thirdly:  From the total absence of the disease in Ireland and Scotland, where the men-servants are not employed in the dairies. [Footnote:  This information was communicated to me from the first authority.]

Fourthly:  From having observed that morbid matter generated by the horse frequently communicates, in a casual way, a disease to the human subject so like the cow-pox that, in many cases, it would be difficult to make the distinction between one and the other. [Footnote:  The sound skin does not appear to be susceptible of this virus when inserted into it, but, when previously diseased from little accidents, its effects are often conspicuous.]

Fifthly:  From being induced to suppose, from experiments, that some of those who had been thus affected from the horse resisted the smallpox.

Sixthly:  From the progress and general appearance of the pustule on the arm of the boy whom I inoculated with matter taken from the hand of a man infected by a horse; and from the similarity to the cow-pox of general constitutional symptoms which followed. [Footnote:  This case (on which I laid no inconsiderable stress in my late treatise, as presumptive evidence of the fact adduced) seems to have been either mistaken or overlooked by those who have commented upon it. (See Case XVIII, p. 36.) The boy, unfortunately, died of a fever at a parish workhouse before I had an opportunity of observing what effects would have been produced by the matter of smallpox.]

I fear it would be trespassing too far to adduce the general testimony of our farmers in support of this opinion; yet I beg leave to introduce an extract of a letter on this subject from the Rev. Mr. Moore, of Chalford Hill, in this county: 

“In the month of November, 1797, my horse had diseased heels, which was certainly what is termed the grease; and at a short subsequent period my cow was also affected with what a neighbouring farmer (who was conversant with the complaints of cattle) pronounced to be the cow-pox, which he at the same time observed my servant would be infected with:  and this proved to be the case; for he had eruptions on his hands, face, and many, parts of the body, the pustules appearing large, and not much like the smallpox, for which he had been inoculated a year and a half before, and had then a very heavy burthen.  The pustules on the face might arise from contact with his hands, as he had a habit of rubbing his forehead, where the sores were the largest and the thickest.

“The boy associated with the farmer’s sons during the continuance of the disease, neither of whom had had the smallpox, but they felt no ill effects whatever.  He was not much indisposed, as the disease did not prevent him from following his occupations as usual.  No other person attended the horse or milked the cow but the lad above mentioned.  I am firmly of opinion that the disease in the heels of the horse, which was a virulent grease, was the origin of the servant’s and the cow’s malady.”