shields the constitution from the Smallpox, and the Smallpox proves a protection against its own poison, yet it appears that the human body is again and again susceptible of the infectious matter of the Cowpox.

In 1780, when attending to Horses with sore heels, Smith conveyed the equine infection to Cows, " and from the Cows it was communicated to Smith. In 1791, the Cowpox broke out at another farm where he then lived as a servant, and he became affected with it a second time; and in 1794 he was so unfortunate as to catch it again. The disease was equally as severe the second and third time as it was on the first." He was twice inoculated with Smallpox in 1795, and exposed to Smallpox without effect.

X.-SIMON NICHOLS, Farm Servant.

In 1782 was employed in dressing the sore heels of Horses, and at the same time assisted in milking Cows, thereby infecting them and generating Smallpox. Changing his situation, he communicated the disease to other Cows, and was himself severely affected. Some years afterwards, he was inoculated with Smallpox by Jenner without effect.

XI.-WILLIAM STINCHCOMB, Farm Servant.

In 1782 had Cowpox severely on the same farm with Nichols. In 1792 he was inoculated with Smallpox along with a large party, but in his case without result. "During the sickening of some of his companions, their symptoms so strongly recalled to his mind his own state when sickening with the Cowpox, that he very pertinently remarked their striking similarity."

XII.-HESTER WALKLEY, Farm Servant.

In 1782 had Cowpox when she was attended by Jenner. In 1795 she, and seven other pauper women of Tortsworth, who also had had Cowpox, were inoculated with Smallpox by Henry Jenner without effect. "This state of security proved a fortunate circumstance," observed

Jenner, as many of the poor women were at the same time in a state of pregnancy." Why then, it might have been asked, did Henry Jenner try to variolate them?

These Twelve Cases illustrate Jenner's procedure; and those familiar with scientific methods, and the scrutiny and caution requisite to arrive at trustworthy physiological data, will view with some astonishment his free and easy induction. In the majority of the Cases he was without proof that his subjects had suffered Cowpox; and the absence of this certainty was the more remarkable as he knew that the dairy-folk described as Cowpox several varieties of eruption. The same rural observers who held that Cowpox averted Smallpox, also held that Smallpox averted Cowpox; and yet Jenner had to show in Rodway's Case No. vii., that they were mistaken; although, granting the thesis that Smallpox and Cowpox were equivalents and mutually preventive, the rural faith ought to have stood justified, and Smallpox shown to be good against Cowpox. Again Jenner allowed that an attack of Cowpox did not prevent a subsequent attack of Cowpox, saying

It is singular to observe that the Cowpox virus, although it renders the constitution insusceptible of the variolous, should nevertheless leave it unchanged with respect to its own action.

Singular indeed! The observation in presence of the principle to be established was nothing short of imbecile. If Smallpox prevented Smallpox, and Cowpox was one with Smallpox, and Cowpox did not avert Cowpox, how was Cowpox to avert Smallpox? The insusceptibility of Jenner's subjects to variolous inoculation was, as observed, of little account. Resistance to inoculated Smallpox was of common occurrence, and inoculators practised various dodges to overcome it. To have made such experiments approximately conclusive would have required the inoculation with Smallpox of subjects of corresponding ages and temperaments who had not passed through Cowpox; and the probability is that the results would not have been dissimilar.

We must not, however, proceed farther until Cowpox is described; and for that purpose I cannot do better than cite Jenner verbatim.

JENNER'S DESCRIPTION OF COWPOX.

Cowpox appears on the nipples of the Cows in the form of irregular pustules. At their first appearance they are commonly a palish blue, or rather of a colour somewhat approaching to livid, and are surrounded by an inflammation. These pustules, unless a timely remedy be applied,* frequently degenerate into phagedenic [spreading] ulcers, which prove extremely troublesome. The animals become indisposed, and the secretion of milk is much lessened.

Inflamed spots now begin to appear on different parts of the hands of the domestics employed in milking, and sometimes on the wrists, which run on to suppuration, first assuming the appear- · ance of the small vesications produced by a burn. Most commonly they appear about the joints of the fingers, and at their extremities; but whatever parts are affected, if the situation will admit, these superficial suppurations put on a circular form, with their edges more elevated than their centres, and of a colour distantly approaching to blue. Absorption takes place, and tumours appear in each axilla [arm-pit].

The system becomes affected, the pulse is quickened; shiverings, succeeded by heat, general lassitude and pains about the loins and limbs, with vomiting, come on. The head is painful, and the patient is now and then even affected with delirium. (P. 3.)

And Jenner might have added, with convulsions.

Having drawn this alarming picture of the effects of Cowpox, he interposes

These symptoms arise principally from the irritation of the sores, and not from the primary action of the vaccine virus upon the constitution. (P. 5.)

If Cowpox meant all this, some might prefer, at least, the risk of Smallpox; hence the judicious explanationthe irritation of the sores, and not the poison in the blood, was the cause of the distressing symptoms. Jenner went on

These symptoms, varying in their degrees of violence, generally continue from one day to three or four, leaving ulcerated sores

*Such timely remedies were solutions of sulphate of zinc or sulphate of copper-a hint for those in quest of antidotes for Vaccination.

about the hands, which, from the sensibility of the parts, are very troublesome, and commonly heal slowly, frequently becoming phagedenic, like those from whence they sprang. During the progress of the disease, the lips, nostrils, eyelids, and other parts of the body, are sometimes affected with sores; but these evidently arise [How evidently?] from their being heedlessly rubbed or scratched with the patient's infected fingers. (P. 5.)

It was this serious disease, this communicated Cowpox, which the subjects of the foregoing Cases were assumed to have passed through; and Jenner, in conformity with the opinion of the dairies, held that they were thereby rendered proof against Smallpox. Whilst his Twelve Cases make a show of inquiry, they bear no trace of extensive or critical research. In the general inoculations then prevalent, those who had undergone Cowpox were not treated as protected (as were those who had had Smallpox) but were "cut" with their neighbours -as, in Case xii., were the eight cowpoxed paupers of Tortworth. Yet Jenner was at no pains to collect and set forth the evidence of other Gloucestershire practitioners, who, in the course of duty, must have known as much of Cowpox as himself, and might have set scores of Cases alongside his perfunctory dozen.

Having perused Jenner's description of Cowpox, let us now turn to his account of its origin.

GENERATION OF COWPOX IN HORSEGREASE.

There is a disease to which the Horse, from his state of domestication, is frequently subject. The Farriers have termed it THE GREASE. It is an inflammation and swelling in the heel, accompanied in its commencement with small cracks or fissures, from which issues a limpid fluid, possessing properties of a peculiar kind. This fluid seems capable of generating a disease in the human body (after it has undergone the modification I shall presently speak of) which bears so strong a resemblance to the Smallpox, that I think it highly probable it may be the source of that disease.

In this Dairy Country a great number of Cows are kept, and the office of milking is performed indiscriminately by Men and Maid Servants. One of the former having been appointed to apply dressings to the heels of a Horse affected with the malady I have mentioned, and not paying due attention to cleanliness, incautiously bears his part in milking the Cows, with some particles of the infectious matter adhering to his fingers. When this is the case,

it frequently happens that a disease is communicated to the Cows, and from the Cows to the Dairy-maids, which spreads through the farm until most of the cattle and domestics feel its unpleasant consequences. This disease has obtained the name of THE COWPOX. Thus the disease makes its progress from the Horse (as I conceive) to the nipples of the Cow, and from the Cow to the Human Subject. (Pp. 2 and 6.)

This conception of the origin and progress of the disease was not Jenner's specially: he shared it with the farmers to whom it was a novelty

The rise of Cowpox in this country may not have been of very remote date, as the practice of milking Cows might formerly have been in the hands of women only; which I believe is the case now in some other dairy countries; and consequently that the Cows might not in former times have been exposed to the contagious matter brought by the men servants from the heels of Horses. Indeed a knowledge of the source of infection is new in the minds of most of the farmers in this neighbourhood, but has at length produced good consequences; and it seems probable from the precautions they are disposed to adopt, that the appearance of the Cowpox here may either be entirely extinguished or become extremely rare. (P. 56.)

Thus Cowpox was to be extinguished by forbidding milkers to handle Horses' greasy heels. Jenner himself tried to produce Cowpox in the manner described, but without success—

It is very easy [he wrote] to procure pus from old sores on the heels of Horses. This I have often inserted into scratches made with a lancet on the sound nipples of Cows, and have seen no other effects from it than simple inflammation. (P. 45.)

What was requisite for success, he concluded, was the limpid fluid from the Horse's heel at an early stage of the disease, and that it should be applied to the Cow's nipples at a certain season—

The virus from the Horses' heels is most active at the commencement of the disease, even before it has acquired a pus-like appearance; indeed I am not confident whether this property in the matter does not entirely cease as soon as it is secreted in the form of pus. I am induced to think it does cease, and that it is the thin darkish-looking fluid only, oozing from the newly formed cracks in the heels, similar to what sometimes appears from erysipelatous blisters, which gives the disease. Nor am I certain that the nipples of the Cows are at all times in a state to receive the