the case should be normal and typical. Hence every case should be held under observation by the operator to that extent which will allow him to recognize all the processes of maturity and note any deviation from a typical standard. The physician who renders this service acts under an implied and recognized duty to confer upon the patient, by the operation, the most complete and perfect protection against small-pox, which vaccination is capable of doing. To do less than this is a violaation of an assumed obligation and a stigma upon his noble and beneficent calling. It is obvious that this demand cannot be conscientiously met without much careful study and patient observation. There should be no uncertain guess-work, but knowledge based upon the study of the best approved methods and careful personal observation. This being so, the folly of confiding this operation to nurses, midwives, barbers or any other party excepting the intelligent physician, becomes apparent. He alone is capable of appreciating any significant or important deviation in the progressive evolutions of the pock, which should cast suspicion or distrust upon the operation. Any such deviation demands a renewal of the operation, under conditions which shall be, if possible, more favorable to success. The failure to do this gives false security which raises questions of doubt in the minds of many as to the prophylactic value of vaccination. A failure to appreciate a perfect operation costs a large annual tribute of human life. Until the consequences that may result, indeed are almost sure at some time or other to result, from the bad and unskillful performance of this operation have taken thorough possession of the public mind, these faulty operations will continue to be found.

2-THE VIRUS USED MUST BE VIGOROUS AND OF UNDOUBTED PURITY OF STOCK.

This is a matter of the utmost importance. This condition of success needs no argument. When enfeebled or deteriorated lymph is used, a limited modification of the susceptibility of the system to the vaccinal and variolous disease is produced. Under this condition a subsequent vaccination, even with the most active and vigorous lymph, results in only a modified expression of the vaccinal disease. As a rule, it is not possible to secure a typical vaccinal expression when once the system has been brought under the partial influence of vaccinia by enfeebled or deteriorated lymph; hence the great necessity that in all cases vigorous and active lymph should be used so that the system shall be thoroughly saturated and hence thoroughly protected by its influence.

The lymph should be taken only from perfectly healthy subjects and from thoroughly characteristic pocks,

Previous to the introduction into this country, in the autumn of 1870, of animal vaccine, and its propagation for general or commercial use, the supply of good reliable lymph of the humanized form was very limited and inadequate to meet a sudden demand. Upon the appearance of small pox in a community, it was often

difficult to secure from any known source that of undoubted purity and vigor. The urgent necessities of such outbreaks have been met by such material as was available, and hence a large amount of vaccination has been performed which was undeniably spurious and unprotective. Furunculous sores have been produced in infinite numbers, which by the ignorant and uninstructed have been accepted as the genuine protective vesicle of vaccinia. The very miscellaneous way in which physicians have so often been compelled to procure lymph has served to greatly increase the number of those who are resting in a false security. A great error also prevails in the community even among those who entertain no doubt as to the necessity and propriety of this operation, in that so many neglect this simple duty until prompted to it by an outbreak of small pox, and the presence of real danger. At such times there is great danger that the operation may be hastily and imperfectly performed, and with carelessly selected lymph, for there is generally a pressure upon the operator for virus which he is not able at once to meet, and the temptation is great, and probably not always resisted; to use material which in times of less excitement and pressure would be rejected. This operation should never be left to a season of panic.

It is the opinion of careful observers of the vaccinal disease that the character of the vescile is an index to the protection produced. As a general rule it may be said also that the results obtained by the use of virus are a good indication of the strength and perfection of the stock from which it come.

Liquid lymph taken upon a surface-an ivory point or quill slip -at the period of its greatest activity, a period just anterior to the full pronouncement of the areola, is without doubt the very best form in which vaccine virus can be used. In this form it possesses all the possible vigor inherent in the stock and at the same time has little or no animal matter mixed with it. In this form there is little danger of transmitting in the subject diseased, germs, which it is possible may exist in the decomposing animal matter always found in the crust.

It is confidently believed that a large amount of spurious, enfeebled and not wholly protective virus has been used through these many years past in this country.* That such has also been the case in England appears evident from the recent report of Registrar General, wherein he shows that the deaths among those who had been vaccinated were 13.5 in each hundred cases, a rate only to be accounted for by reason mainly of the too general use of humanized virus which has failed to give the maximum of protection.

It is not within the purpose of this report to discuss, at length, the relative merits of animal virus as compared with humanized. We give it as our opinion that properly selected humanized virus of the first remove from the heifer, by human transmission, will afford as perfect a protection as is possible to besecured. But the humanized virus is so very generally procured and used under such

See report on vaccination by the writer in Transactions of Wisconsin State Medical Society, 1874.

varied vicissitudes and with such an imperfectly understood history, that a conscientious operator must often entertain doubt as to its vigor and the certainty that it will give the maximum of protection. It is a question whether there is any vaccine in use in this country whose pedigree is known and which is worthy of confidence, excepting that which is produced from the calf or can be traced to that source through a few near removes by human transmissions.

Every operator is held by public sentiment and considerations of professional honor to the exercise of the greatest vigilance and care in the selection of humanized virus. Experience has demonstrated that the vaccinal disease, when imparted to certain subjects, produces in them an imperfect or modified development, and that lymph taken from such subjects has so far lost its character, when perpetuated through other subjects, as to give rise to an imperfect vaccinal disease. There is then under certain circumstances, a degeneration of virus taking place; once we can readily understand that when virus is carelessly selected, this may seriously damage the degree of protection. Hence in the choice of virus, special reference should be had to its quality. This will lead to a knowledge of its origin. If it is animal virus, it should have an accredited pedigree and must be propagated under the direction and by the hands of a thoroughly competent person. If of human origin we should know its remove from the heifer, and that it has been propagated through healthy and vigorous persons, and those vaccinated for the first time. I think nearly all operators who have carefully studied this subject advise the use of heifer lymph when it can be obtained. When this is not accessible, that which is only a few removes from it. The nearer the better.

The use of heifer lymph not only ensures the maximum of productive influence, but removes all possible objection on the part of any who are unwilling to subject themselves or their families to the operation through fear of the introduction into the system of some associated disease. While it is found that the possibility of transmitting diseases by vaccination is far less than is generally supposed, and that this possibility can be asserted positively only of syphilis, nevertheless in a procedure which so many contend against, and which, especially in the minds of the laity, is so objectionable, even the appearance of error must be most scrupulously avoided, not only for the personal interests of the physician, the interest, especially of good cause," [Curschman.]

Dr. Geo. E. Walton, of Cincinnati, in a recent paper upon the

"6 COMPARATIVE MERITS OF ANIMAL AND HUMANIZED VIRUS."

3. THE OPERATION SHOULD BE REPEATED AS OFTEN AS NECESSARY TO TEST THE RETURNING SUSCEPTIBILITY OF THE SYSTEM TO THE SMALL-POX CONTAGION.

It is quite evident that the public mind is uninformed and unsettled in its convictions upon the protective range of a primary vaccination and the necessity of a re-vaccination. Jenner taught that protection from vaccination was life-long. The expectations begotton by him and the early teachers that a successful primary vaccination in infancy or early childhood would give security against an attack of small-pox for the remainder of life, are cherished, through ignorance of facts, by a great many at the present time, and this supposed security becomes their greatest source of danger. "Best safety lies in fear.”

Less than twenty years had passed after the discovery and promulgation of the practice of vaccination, when it began to be observed that some of the vaccinated took on a mild form of smallpox. The experience of three-quarters of a century has proved, beyond all question, that the protection afforded by this practice is not life-long. Though most effective in mollifying the disease, it is not to so great an extent a preventive as was once believed.

The question as to how long will the protective influence of a perfect vaccination in infancy or early childhood last, cannot with certainty be answered. All careful observers are agreed that this protection is for a few years, certainly, reliable and complete. It

is certain that one person may be protected for a longer time than another. The range of susceptibility to any contagion is very wide in the human family. One individual will contract disease while another equally exposed will escape. The evidence is very abundant, that, apart from all faults in the operation or of any enfeeblement in the virus used, there occurs, from natural causes, a tendency towards a return of the susceptibility to small-pox contagion, commencing probably not very long after primary infantile vaccination, increasing with the growth of the child, gaining intensity at about the puberic period, which does not diminish again except under advancing age. After infancy is passed the period of life in which most persons are liable to contract small-pox is from fifteen to twenty-five years of age. It is the same with the vaccinated and the unvaccinated, although the degree of liability is not the same. [Ballard.] Hence it is that revaccination is recommended, not because it is absolutely necessary for all, but because it is impossible to predicate who among the multitude vaccinated in infancy has re-acquired a receptivity to the contagion.

Comparatively few, in this country, at least, entertain doubts as to the necessity or propriety of a primary vaccination, but with regard to revaccination it is feared that the great bulk of the people have no intelligent and well settled convictions as to the time when a revaccination should be performed or the absolute necessity for such an operation. I wish it were possible to bring home to the minds and belief of the general public an intelligent and abiding conviction regarding revaccination-that it is a means by which we may secure almost absolute protection against any form of small-pox, and reduce the death rate from that disease to an absolute zero. In those countries in Europe where vaccination has been thoroughly performed, followed by universal revaccination, small-pox is all but annihilated, and deaths from it unknown.

"It is unfortunate," says Bousquet, "that art or nature has no sign to distinguish between those who need vaccinating and those who do not." Hence the practice should be universal.

"A small portion of vaccinated persons are protected through life by one operation; an indefinite number only for a certain period of time. The length of time they are thus protected is undetermined. Hence we are forced to admit that as a means of protection, revaccination is as important as a primary operation."

Since there is no known law governing the duration of the protective influence of a single vaccination, and since this period of protection varies widely in different individuals, it is safe, with our present knowledge, to advise that revaccination should be practiced every five years. It is better that the period should be needlessly short than too long. If small pox is prevalent in a community, the circumstances of the case should dictate the operation rather than the period of time only.

In reviewing the great mass of testimony upon this subject there is but one conclusion at which we must arrive, when considering the utility and desirableness of revaccination. While it is not wise to subject the individual or the public to any useless incon