While Willan recognizes it only as presented in the serous or vesicular form, Rayer acknowledges that it occasionally assumes a pustulous condition. With regard to the grade, which is made the source of distinction between distinct and confluent smallpox, it should be remembered that Ring has given us a case of confluent chicken-pox, and that McIntosh has recorded two fatal cases, one in a child, the other in an adult. Heberden speaks of a malignant sort of chicken-pox, in which "the continuance of the pain and fever, after the eruption, and the degree of both these, though there be not above twenty pustules, are, as far as I have seen, what never happens in the smallpox." Chicken-pox has been known to pit the skin, and distinct smallpox often fails to do this. If we receive the diagnosis of McIntosh and others, who discern chicken pox by the succession of crops and pustules, what shall we say to Heberden's acknowledgment of its unequivocal occurrence in four cases of smallpox? These are "the only instances" he says, and his language is striking, "which have happened to me, something like what is so often talked of, a second crop."

It seems to me that the above observations, which I have taken in preference from the older writers, exhibit plainly enough the difficulty, occasionally presenting itself, of distinguishing smallpox from its kindred affections, if indeed they do not establish an identity of character and origin between them.

I allude to those which are familiarly included under the newlyinvented term varioloid, first used by Thompson in describing an epidemic, which prevailed at Edinburgh in 1811.

The diagnosis of small-pox, as separating it from varicella, though spoken of very slightly by Gregory, cannot be a matter of such practical facility as he represents it. I have myself seen and known mistakes made on the subject. Thompson, a very competent observer, maintains their identity; and his facts are not easily set aside, nor his arguments readily answered. Bateman, too, closely attached as he was to Heberden's and Willan's views, found reason to doubt their correctness here, as appears from a letter written by him to Dr. Howitz, of Copenhagen, in which he says: "I am much inclined to concur with you in the supposition that chicken pox is, in fact, modified smallpox."

In the 5th vol. of the Trans. Am. Assoc. we find it stated that about the middle of Jan'y, 1851, smallpox broke out in the jail of Montgomery, Alabama. The first case was that of a negro man, recently from New Orleans, who said that he had been, a short time before, in attendance upon a gentleman, "who was said to have chicken pox."

In the winter of 1853, a member of the Class of the Charleston Medical College died of smallpox. He received the infection from a case pronounced by a respectable physician to be chicken-pox, which was in this way the centre of a considerable number of attacks.

Perhaps we shall best be able thus to explain the occasional occurrence of smallpox, to all appearance spontaneously arising, or under circumstances that forbid all usual explanation; as in the instances formerly referred to in the Pennsylvania Penitentiary; in Lawrenceville, Illinois, as related by Dr. Banks; and that which came under my own notice in the Charleston Workhouse. The irregular and anoma

lous forms of the disease, described by Huxham and others, and known by the quaint names of horn-pock, water-pock, chrystalline-pock, swinepock, sheep-pock, and so forth, are now called by the common title of chicken-pox, or sometimes denominated technically varioloid, as resembling smallpox, but yet differing from it. Thus we avoid the excitement of an inconvenient and annoying panic. We evade all the evils and pecuniary and other injuries of exclusion, seclusion and quarantine, and when the infection of a susceptible individual develops the disease in its true and unmodified character, we have lost the clue which would direct us to its actual source.

The varieties and irregularities which we know to have formerly presented themselves in variolous epidemics, arose perhaps in part from local contingencies; perhaps from tribal peculiarities or special habits, manners, and customs; perhaps from individual idiosyncrasies. All these produce similar effects now, and under our own eyes; as may be seen in Dr. Thompson's history of his observations, in the course of which he saw mingled together, and to all appearance traceable to the same source, examples of "uncommonly severe disease, not to be distinguished from smallpox, and the mildest variety ever described of chicken-pox."

To all these is now added a more general and widely diffused disturbing or modifying cause-the influence, namely, of the vaccine; and hence, at the present day, we meet with more frequent and more definable modifications than formerly.

VACCINIA, the vaccine, of which I now proceed to treat, derives its origin from the cow-vacca. It was first made known to the medical profession in 1798, by Dr. Jenner, whom we rank unhesitatingly among the greatest benefactors of the human race.

The history of vaccine is an exemplification of the acute remark of Southey, in his Omniana, that "most things are known before they are discovered." Prela, physician to the Pope in 1825, contends plausibly, from passages in Pliny and Celsus, that the vaccine was known to the ancients, under the name of boa. It was certainly in use in Hindostan long ago. In Gloucestershire and Dorsetshire, two of the dairy counties of England, it had been observed from time immemorial that their cows were occasionally affected with a species of ulceration about the udder, which communicated to the hands of the milkers a pustular eruption. The occurrence of this eruption was noticed to have conferred upon such persons a security against the casual infection of smallpox; and such was the "general opinion," says Parr, "that the inoculator who attempted to convey the smallpox to one who had been thus previously affected with vaccine, was ridiculed." There was no difficulty in following up so plain a hint; and the "artificial communication of this disease, as a preventive of variola, was tried first by a farmer of that county, and afterwards by Dr. Jenner, with the most satisfactory results. The early writings of the latter on this subject were received with scorn, and his papers refused publication among the Philosophical Transactions. It, however, forced its way into notice; the value of the discovery was, after vehement and angry

debate, established on the most authentic basis, and the zeal of its promulgator amply rewarded by the British Parliament. Since that time the vaccine has been extended all over the globe, and all nations of mankind have exulted in the benefits thus bestowed upon them. To the present time it has enjoyed the undoubting confidence of the profession, and at once superseded, and almost entirely suppressed, the practice of inoculation.

Vaccination is performed by introducing under the cuticle a small portion of lymph, taken from a vesicle about the eighth, ninth, or tenth day, while yet the fluid distending the vesicle is transparent and colorless. The puncture remains unchanged until the third or fourth day, when slight elevation and inflammation are perceptible, which increase slowly. About the sixth, it assumes a regular circular form, with a depression in the centre. The vesicle is completely developed on the eighth or ninth day, and attains the average diameter of onethird of an inch. An areola now surrounds it, of an intensely florid red color, and some febrile excitement of the system is perceptible, with stiffness, pain, and slight swelling under the arm, if the vaccination be performed about the usual spot, above the elbow. The diameter of the areola differs from one to two inches. It is attended with a degree of roughness, hardness, and intumescence of the skin over which it spreads-circumstances which denote its existence and extent in the black. The vesicle is multicellular, that is, composed internally of numerous spaces or little cells, which communicate freely with each other. The fluid within these cells begins to dry away on the eleventh or twelfth day, having previously lost its transparency, and become milky, or straw-colored; the areola at the same time declines, and gradually disappears. About the twenty-sixth day, a hard, round scab, of rosewood color, smooth on the outside, and remarkably hollowed in the centre, falls off, leaving a permanent cicatrice, of peculiar and characteristic aspect-its surface being marked with minute pits or depressions, similar to those on the head of a thimble, “denoting," probably, "the number of cells of which the vesicle has been composed." It was stated above, that in variolous inoculation, the vesicle forming at the point of insertion is accompanied by the eruption of others in different parts of the body; this, as respects vaccine, is a fact of very rare occurrence. Two such instances, however, have been communicated to me.

I shall not attempt to describe any of the numerous deviations from the above history, which are to be met with in the irregularly diversified forms of what are called "spurious vesicles." Suffice it to say, that any striking or obvious departure from the ordinary phenomena, in the progress of a vaccine pustule, should make us cautious of confiding a patient to its protective influence. Vaccine, like every other disease, may undergo certain modifications from the condition of the recipient, an infinite majority of which are slight and unessential, not affecting its character and influence, nor impairing its genuineness. Others there are, however, though few in number, which change the nature of the specific action, either locally or in its effect upon the system, and thus render it "spurious." Of the local modifying causes,

the principal and most common is the mechanical irritation of the vaccinated spot (as by rubbing), by which a common inflammation is substituted for the specific, and a common sore produced. Erysipelatous inflammation may also supervene, and interfere with the formation of a regular vaccine pustule. Vaccine may, perhaps, be affected by or combined with some forms of constitutional disease, and thus take on a hybrid state. All cutaneous affections disturb the regularity of its progress, if they do not hinder the success of the operation; and no physician should employ vaccine lymph from a pustule on the arm of a patient known to labor under scrofula, herpes, or lues venerea.

I am disposed to lay some stress upon the progress of maturation of the vesicle, although this may be slightly hastened or impeded, without detracting from the value of the pustule. Thus, the temperature of the season, if high, may occasion it to anticipate twenty-four or thirtysix hours perhaps; and severe cold, on the contrary, by checking the cutaneous circulation, may retard it in an equal degree. The debility or robustness of the subject may give rise to like results.

The pustule should be prominent and clearly defined, and the areola distinct and vivid. There should attend some febrile disturbance of the general system. The appearance of the scar, as above described, I consider of much importance. We should revaccinate when this peculiar appearance is wanting, and when the scar is smooth, or resembles that of a burn.

I do not find the observation made by any writer, but I have certainly noticed the occurrence of a doubtful or spurious vesicle to cause much difficulty in procuring, subsequently, the satisfactory results of vaccination in the production of a regular or genuine pustule.

Vaccination is, of course, best and most successfully performed with fluid lymph, taken immediately from the vesicle, but this simple mode of communication is not always possible. When required to be transported to a distance, or kept for any length of time, it may be preserved by various methods. The fluid is caught on a small plate of glass, which is pressed closely against another of similar size and shape, and the edges waxed, to prevent the access of air. We receive it on the points of quills, likewise protected from the air by envelops. Cotton thread is dipped in it, and laid aside with equal care. But in the scab we have the most convenient means of preserving and transporting this invaluable agent. It has been kept for years, and found capable of communicating the genuine disease, just as when recent. It may be protected from the contact of air and moisture, by immersion in softened wax and spermaceti. It is scarcely necessary to remark, that the first scab alone possesses the specific vaccine character; if this falls off, or is rubbed off too early, another may succeed it, but possesses none of its useful properties.

Climate undoubtedly influences much the susceptibility of the human constitution to vaccine. The missionaries to Siam were endeavoring to introduce it into that country many years before they suc ceeded. Perhaps this may have been owing in part to the difficulty of preserving the vaccine in very hot weather. This is well known in the southern States, where it is common to cease vaccinating during

the warm months, and procure a new supply of vaccine from the North at the approach of winter.

Some have strenuously urged the propriety of recurring occasionally to the udder of the cow, the original source of vaccine, to insure its genuineness, and renew it from time to time; but it may now be looked on as settled, that its primary and essential characteristics are unchanged and unimpaired by any imaginable number of transmissions. Nay, more, it is obviously improved by thus passing through the human system; it is so modified as to have become a milder malady, though not less effectual in its influence on the constitution. person inoculated directly from the cow, always suffers much more, it is said, than one who receives the infection from a human vesicle, and, as far as has been ascertained, with no corresponding advantage to compensate.

Among the animals which have been found capable of receiving and communicating the vaccine, are the horse, the ass, the camel, the buffalo, the goat, the sheep, and the baboon.

It has been doubted whether variola does not exert a reciprocal influence upon vaccine, whether it tends to prevent its introduction into the system, or in any manner or degree modifies it, and disturbs its regularity when so received. But the most positive proof has been obtained of the transmission of perfect vaccine through constitutions previously subjected to the variolous impression. It has been, in this way, brought across the Atlantic, by the successive vaccination of individuals among the passengers and crew of the vessels, many of whom were known to have had the smallpox. This is one among the facts which make me still doubt the correctness of the opinion that vaccine is only variola, modified by passing through the system of a lower class of animals.

Much has been said of the difficulty of communicating the disease more than once to the same constitution. Gregory, of the smallpox hospital, declares that "it is impossible, or nearly so, to reproduce the vaccine, in anything like its genuine form, when the cicatrix left by a preceding pustule is perfect, and the result of a perfect vesicle."

Dr. Darrach, of Philadelphia, in experimenting on this subject, found that the repeated insertion of the matter in the arms of vaccinated children, occasioned a local disease exactly similar to that produced by the first operation, with the exception that the pustule and scab were much diminished in size. In none of these cases could fever, or any other constitutional effect, be discovered. Unprotected children were, with complete success, vaccinated from one of these scabs, not larger than a line (one-twelfth of an inch in diameter), which was the result of a fourth insertion of the virus.

The duration of the influence of the vaccine-the permanency, rather, of the effect which it has wrought upon the system-has been denied by some who are stanch believers in its temporary power to destroy the susceptibility of the body to the invasion of smallpox. But the mass of facts collected under this head, certainly goes to prove that whatever may be the result of the vaccine inoculation-whatever the impressions made by it upon the organism-this result, these impres