If the variolous inoculation had continued to be equally important, we should have reckoned it our duty to insist still more largely on the preceding particulars. But this has ceased to be the case, not indeed from any failure of this form of inoculation, but from the substitution of ano ther, which is still more advantageous. For a more par ticular account of the preceding part of the subject, we refer to the works which we have already mentioned, and also to the interesting history of Inoculation of the Small pox, by Dr. Woodville, which, in a great measure, super sedes every other to the modern reader. That work abounds in apt quotations, and is, on the whole, one of the most interesting specimens of medical and literary history with which we are acquainted.
We proceed to describe the form of inoculation now practised, which is commonly called VACCINATION, or THE Cow-Pox, one of the most brilliant discoveries of modern times, and which, at present, derives a great interest ft om the scope which it still affords for speculation and experi mental inquiry. It is founded on an extraordinary power possessed by a disease incident to the cow, and capable of being communicated to man, viz. a power of obviating the susceptibility of the system to small-pox. The exist ence of such a power, derivable from such a soul ce, though often asserted by individuals, appeared incredible to per sons most extensively acquainted with all the facts in pa. thology received among the learned, and the accounts of it were disregarded as vulgar fables. Since it has been as certained, it must be considered as a death-blow to that sceptical incredulity which gratuitously rejects all novel suggestions previously to their plausible introduction into intelligent circles. It is too common to find medical men, whose information extends no farther than the routine of the day, cherishing their self•complacency with a semblance of systematic reasoning, and asking with incredulity, when any thing new is proposed, what good it can do ? This spirit contracts greatly the sphere of salubrious expedients. 'We Have no right to deny the existence of a power till we have disproved. \Ve have no right, indeed, to assert the existence of any power without evidence ; but we may figure to ourselves the possibility of it for the purpose of instituting experiments, or watching coolly the results of experiments made by others. After the discovery of the cow-pox, we find, accordingly, that the shock given to in credulity produced among its enthusiastic advocates a fer tile suggestion of experiments, and a description, by antici pation, of numerous supposable discoveries. We cannot, however, advance as a point in science any principle which has not been actually ascertained. The truths known to us respecting the cow-pox are worthy of the attentive con templation both of the philosopher and the philanthropist, and furnish matter for further research, as equally sub servient to the extension of science, and the securing of ad ditional advantages to human society.
For this discovery we are indebted to the now celebrated Dr Jenner. 'It was previously known among persons con cerned in several large dairy farms, that the disease, when received by accident from the teats of the cow, protected the human system against small-pox. Inoculation with it
is said to have been practised in some instances by obscure individuals. Several years before Jenner wrote on the subject, some eminent physicians had heard of it, and men tioned it casually in their writings, but never with that pointed seriousness which was suited to so great an object. Dr Jenner was the first who wrote a treatise for the ex press purpose of bringing it into view, and extending its beneficial application. This was in 1798, and the treatise was entitled " An inquiry into the Causes and Effects of the Variolte Vaccinx, a disease discovered in some of the western counties of England, particularly Gloucestershire, and known by the name of the Cow-Pox." lie did not blazon his discovery with the enthusiastic eve4itz of Pytha goras. He exhibited the facts with that philosophic cool ness, which placed a just confidence in the candour and the enterprising spirit of the age ; and he quickly found a band of warm coadjutors in the investigation of the subject, and the extension of the knowledge of it. Among these, Dr Pearson of London was one who united much zeal with enlightened caution. He collected a copious body of in formation : he urged several important inquiries, and he availed himself extensively of his opportunities of ascer taining the laws of cow-pox by experiment. It would be unnecessary to mention the names of many others who were conspicuous for their exertions in the same cause. In all parts of this island, and in every country of the civil ized world, it was hailed by enlightened men as an import ant discovery, and they eagerly sought for opportunities of giving it universal currency. It was sent to the most dis tant countries, and spread even among the most unpolished nations ; and it is now problematical, whether any tribe on the face of the earth has not already experienced its bene ficial operation. Prejudices have existed against it, but have been generally subdued by the gradual introduction of correct habits of thinking. Alarms have, indeed, been sounded against it, even by men of liberal education. In stances of this, however, have been few. They have arisen from accidental occurrences, rashly construed into the ope ration of constant natural causes. Zeal was precipitate in its movements on both sides of this momentous question ; and the unblushing contention for fame, which on some oc casions appeared, was ridiculous, and worse than boyish. The effervescence which controversy produced has gradu ally subsided. The inoculation with cow-pox has gained ground ; facts of all kinds that occur relative to it are cool ly observed. We cannot, however, boast of being in pos session of a satisfactory knowledge of all the laws of vac cination. Occurrences occasionally arise, which create a doubt concerning the exact extent of its effects, both in exciting and in preventing disease. We shall, therefore, in the remainder of this article, give an account of the principal points which have been ascertained, and take no tice of some desiderata which are not vet fully supplied.