The inconvenience, as well as the disappoint ing results, following the use of humanized vaccine virus gradually resulted in the adoption of another method of propagating and furnish ing the virus. One very prominent reason for this was the increasing fear of transferring a certain infectious disease from person to person through vaccination. Also, in transferring Villeman's experiments regarding the possibility of such danger was given per haps too much prominence. It cannot be denied that there is some slight possibility of the dis ease being transmitted in the process of vaccina tion. Unfortunately, there are cases on record where a grave constitutional disorder has been inoculated into healthy persons by vaccination. Those opposed to vaccination seized upon these accidents, and exploited them in every way pos sible, as a further argument against the control of smallpox by the arm-to-arm method, and as not an unimportant factor in reviving the method of propagating vaccine virus on the bovine species. This method was known to many, and was employed as early as 1800 in France, and by several physicians in Italy at various times between 1805 and 1840— the latter by Negri in Naples, who began the systematic use of bovine vaccine virus. It then was em ployed to a slight extent in several places in Europe, but did not become of general use until many years later. Arm-to-arm vaccination was the method employed in the United States from the time of its introduction until as late as 1869, when animal vaccine virus began to be em ployed. It was not so difficult in our large cities to have available a supply of humanized vaccine virus, but with the growth and increase of the rural population it was not always an easy mat ter to have this supply; so in order to meet this growing demand, bovine vaccine virus was sug gested as being the most practical method of over coming the difficulty. This led to the establish ment of "vaccine farms," as they were desig nated, in several parts of the United States. It was not long after their establishment until the hulk of the vaccinations were performed with the bovine virus, and the arm-to-arm method became the exception to the rule. When calf lymph came into common use, the same diffi culties were apprehended with regard to its at tenuation as were before noted with the humanized virus. Some observers claimed to have noted the good effect of restoring a virus beginning to show attenuation, by retro-vaccina tion— that is, by vaccinating the calf with the humanized virus and back again to the person; in some instances, alternating the virus from calf to man and from man to calf. Also, Cal mette and Gurin of Lille have employed rabbits for producing the virus. The Bavarian gov ernment, as early as 1837, made it mandatory that this procedure should regularly be em ployed for revivifying and maintaining the potency of the vaccine virus. TMs brings us to consider the efficiency of the virus propagated through the bovine species, as compared with the humanized virus. There are many even to-day who contend that the results following the use of bovine virus are not so good nor so typical as those of the humanized virus. The reaction following the bovine virus is milder, the sore not so large nor typical. If we are allowed to form an opinion, from the descriptions of the early writers and their drawings of the vaccine lesions, it must be admitted that they bear out to some degree the statements regarding what is now observed, and what used to be. Follow ing its application, nearly every civilized coun try has adopted and employed the bovine virus. In some, vaccination is optional, while in others it is compulsory. Where vaccination is more largely employed, the frequency of attacks of smallpox diminishes in an equal ratio. Germany may be cited as an example, as a country which has employed the bovine vaccine to the greater number of its population than any other coun try. Vaccination here is made compulsory. All children during their first year are required to be vaccinated, and again at the age of 12. All males subject to military service are vaccinated on being drafted in the army (some 300,000 yearly). The official records for 18% show that 1,518,793 were legally liable to vaccination; 1,321,348 were vaccinated with bovine vaccine virus, and 5,406 were vaccinated with virus of other sources. In primary vaccinations 96.77 per cent were successful. In secondary vac cination, made at the 12th year, there were 1,143,947 legally liable. Of these 1,107,025 were vaccinated with bovine virus and 7,165 with other virus; 91.71 per cent were successful. The wonderful immunity of the German nation to smallpox, resting entirely on its compulsory vaccination laws enacted in 1870, whereby the whole population has been vaccinated and re vaccinated, not only demonstrates the benefits of vaccination per se, but also the efficacy of a virus obtained from the bovine species. Similar cases could also be cited to show the efficacy of the bovine virus. It cannot be said that the immunity conferred by it is any stronger or more lasting than that of the human ized virus, but it has all the advantages and none of the disqualifications which attend the arm-to-arm vaccination.
From jenner's time until now there has been a strong belief that there was an intimate con nection between vaccinia and smallpox, and that the former was in all probability a modified or attenuated state of the latter. Gassons inocu lated 10 cows with matter taken from smallpox cases, and was successful in one instance. After 10 removes the pustule resembled that of a natural vaccine vesicle. These experiments were repeated many times during the past century with more or less success. The most important of them were by Theile of Kasan, Russia (1839), who succeeded in transferring smallpox virus to a cow, and after several removes vac cinated a large number of persons with such virus, the results being in every way the same as observed in the cowpox virus. Ceely, in 1839, and Badcock of England (1840), also suc ceeded in variolating a cow, and obtained the same results as did Theile. Some of this virus (crusts) was sent by him to this country in 1852, to Coale of Boston, Mass. This was used quite extensively in and around Boston with evidently good results. The Lyons commission, with Chaveau as its chairman, also made an ex tensive inquiry into the nature of vaccinia and smallpox. Some of its experiments were in this particular direction. Chaveau's conclusions were that vaccinia was separate and distinct from smallpox, and although the smallpox virus could with great difficulty be transferred to the bovine species, producing lesions closely re sembling those of vaccinia, on subsequent pas sages through other animals it became at tenuated and finally inert. Voigt, of Hans burg, in 1881, also succeeded in transmitting the smallpox virus to a calf, and after several employed it for vaccinating persons. particular strain has been employed by Voigt for all the vaccinations performed In Hamburg from 1881 to 1904, the virus being propagated directly from calf to calf, with an exception that on two occasions (1:!1) it was passed from calf to man, and then in 1902 from calf to rabbit. The results obtained from the employment of this strain are such as to be convincing proof of its potency during all these years, as the percentages of successful vaccina tions in primary cases, ranging from 98 to 100 per cent, and the low percentage of successes in revaccination, 69 per cent, demonstrate the permanency of immunity. The most convincing proof lies, however, in the fact that the popula tion of Hamburg shows fewer cases of smallpox than any other community of same size. The preponderance of evidence accumulated during the past century shows that vaccine is nothing more or less than a modified and attenuated form of smallpox. The latest researches on this subject, as set forth at length by Pfeiffer, Guar nieri and Wasielewski, and of those in particu lar by Councilman and his co-workers on the specific organism of smallpox and vaccinia, seem to leave but little doubt as to their common nature. Brinkerhoff and Tyzzer made an ex tensive enquiry in Manilla in 1904 into the na ture of smallpox and vaccinia, in which they show that smallpox is transmissible to monkeys and orangutan; and that the inoculated small pox behaved in no wise different from the in oculated smallpox in man. Further they suc ceeded in transmitting this inoculated smallpox of the orangutan to calves; and after a few pas sages in calves it was then transferred to man. These inoculations produce typical vaccine lesions and were not different from those of the so-called vaccine. Their experi ments confirm those of Voigt and others to the effect that vaccinia is modified smallpox. About the end of the 19th century the value of re vaccination was becoming better understood, but it required many years before this important fact was appreciated. Even now it is ignored to a considerable extent in some parts of the world, particularly in the United States.
Vaccinia has never been observed to occur spontaneously in man. It is always transmitted by inoculation. The appearance of the inocu lated lesion varies somewhat, according to the manner in which the virus is inserted. The usual methods are: (1) By puncture. (2) By scarification or denudation of the epithelium (abrasion). (3) Hypodermically. If by punc ture, a slight redness occurs at the point of inoc ulation within 24 hours, not different from any slight wound of the skin. In 48 hours a slight redness may be seen around the puncture, which to the touch may give a sensation of a slight elevation of the spot. At 72 hours the spot is visible, slightly elevated, slightly gray in the centre and surrounded with the faintest sugges tion of a pink border or areola. In 96 hours the papule is of a dull whitish color, the border elevated and well outlined. There is usually a depression of the centre — umbilicated, the areola is well marked; the skin around it is bard and begins to be painful and itch. From
the fifth to the sixth day the process still fur ther enlarges and varies from one-fourth inch to one-half inch in diameter. The centre is darker and more depressed, the periphery much more elevated and the edges of a pearly gray color. The sore is filled with a fluid, the areola is of a darker color, the skin just beyond this is softer and less painful. About the seventh day the vesicle becomes flatter, though some what wider, the centre not so much depressed but covered with a crust or scab. The gray zone becomes yellowish and the areola and induration diminished. From this time onward the process gradually subsides, the crest or scale becomes thicker and more elevated, grad ually contracts, and after 15 or 18 days falls off and leaves a completely healed pink and glistening surface, with small, dark depres sions here and there over its area. If the inoculation is made by scarification or incision the same phenomena are observed, save that the process is hastened and is fairly well marked on the second day, with incipient but distinct areola; the central depression, with a distinct gray, pearly margin, elevated and prom inent. The areola and induration are well marked on the fourth day, the gray centre is vesicular and transparent, its external margin irregular; the central depression is quite marked, the areola a bright pink and the sur rounding skin is swollen. The lesion now ad vances more rapidly during the next 24 hours, when the clear vesicular zone becomes a whit ish color, its borders irregular, the central de pression darker and covered with a crust. The areola is not now so prominent nor the indura tion so diffused. It has now reached its maxi no lesion development of the skin proper. In stead there is a slight induration beneath it, which to the touch imparts a feeling of a small shot. This gradually enlarges until the fifth or sixth day, when it soon subsides. The con stitutional symptoms in man are practically the same as those occurring in the animal. There is an elevation of temperature, loss of appetite and thirst and more or less enlargement of the glands nearest to the lesion, which reaches its greatest increase at the height of the devel opment of the pustule. If there is no secondary infection of the lesion by extraneous bacteria the temperature falls to normal, the sore heals and all symptoms rapidly subside. In some very susceptible subjects, particularly in chil dren, vaccination is sometimes followed by a secondary vaccinal eruption. This may be a discreet crop of vesicles occurring at or around the point of inoculation. Sometimes, however, a general eruption may follow. This second crop will go through practically the same phases of development as does the original puncture, only that it is smaller and the indi vidual vesicles have not the same amount of areola and induration of skin as observed at the site of inoculation. The local lesions of inoculated smallpox and vaccinia are quite dis tinct. So also are the constitutional symptoms. In smallpox there is a period of from 12 to 14 days intervening between the exposure to the disease and the appearance of the first symptoms. In inoculated smallpox the period of incubation is much shorter, seven to eight days, before the fever and rash. In vaccinia the incubative period is from five to six days. The difference between each can be illustrated in the following temperature chart (after Hime) : mum development and gradually subsides, heal ing from the 15th to the 18th day. When the virus is inserted by the hypodermic method, and the needle passed into the skin, the appearance of the lesion is much the same as in that by simple puncture, but sometimes there is Recovery from smallpox requires from 30 to 40 days or more; if inoculated, smallpox, 25 days, and for vaccinia, 22 days. The limit given for each is for the time required for the individual to completely recover from the dis ease. Does recovery mean simply that the in fective agent has completed the cycle of its development, and then ceases to exist, or that it is influenced or brought under subjection to certain substances in the body of the host? It is a well-established fact that recovery from any attack of smallpox usually protects the individual against a subsequent attack. So also does vaccination protect against subsequent inoculation, and also protects against smallpox. There is beyond question a change occurring in the body in some way which prevents it again becoming a susceptible reagent to these poisons, a state of resistance or immunity. Some experiments of Sternberg show that the blood of a vaccinated calf, when mixed with a quantity of vaccine virus, destroys its ac tivity. The writer has also observed this. It was found that these substances begin to make their appearance in the blood of a vaccinated animal about the ninth day, and are at the height of their potency at about the 14th day, after which they gradually disappear. Even when these substances (antibodies) have dis appeared, the animal will remain for a long time refractory to vaccination. It, therefore, seems more than probable that two states of re sistance are brought about by vaccinia, one in which the vaccine virus is destroyed by these new substances, and that the body cells have in some manner been so modified that they are no longer in a receptive state to the virus. The same train of reasoning would seem to apply to the state of immunity following an attack of smallpox. The time when the tissues become refractory to the vaccinal process has been es tablished by observation both on man and ani mals. If an animal be vaccinated over a small spot of the skin in successive days, the vacci nated process will develop normally on the first, second, third, fourth, fifth and sixth days; that on the seventh day will show an under develop ment; the eighth day still more so, and the ninth only a slight trace, if any, and that of the 10th day not at all. The immunity is estab lished about the ninth day and will continue for a period more or less long, and sometimes is permanent. Jenner has demonstrated that immunity to both smallpox and vaccinia is very strong, as persons having previously had the cowpox, even years before and subsequently vaccinated with fresh vaccine virus, and even inoculated with smallpox, did not contract the disease. The same also was established in Jesty's cases who were inoculated with small pox virus without result a number of years after vaccination. Immunity to vaccinia can be produced in several ways. We have hereto fore dealt with the method of inoculating the skin of mucous membrane and cornea with vac cine. The Lyons Commission, in 1877, demon strated that a calf or horse could be rendered immune to vaccinia by injecting the virus either subcutaneously or intravenously, and after 9 to 14 days the animal would be refractory to a subsequent inoculation. Several years ago the writer made some experiments regarding this immunity, when conducting an enquiry into the serum therapy for smallpox, in which he con firmed all that had been claimed by the Lyons Commission, Chaveau and others. Not only was immunity established by intravenous and subcutaneous injections of the vaccine virus, but also a rapid immunity could be induced by injecting the virus under the dura water, or into the brain substance. Monkeys could thus be rendered refractory to vaccinia within five days, whereas it could be caused in nine days when the virus was administered intravenously, or by inoculating the skin. It requires a very minute quantity of the virus, either in the form of lymph or pulp, to cause the typical lesion. Chaveau found that by taking lymph from a vaccine vesicle and diluting it as much as 1-20000th, it would cause a typical vaccine lesion. A general vaccinal eruption sometimes occurs in calves and young horses (colts) when a considerable amount of vaccine virus is in jected in the veins, the eruption making its appearance about the fifth day, shortly after the fever. The eruption appears to be nowise dif ferent in appearance than that artificially pro duced by minute punctures. It also resembles the secondary eruption which occasionally fol lows vaccination in children. Vaccinia is chiefly confined to the tissues of the skin, but coincident to the development of the specific eruption the virus can also be demonstrated in the blood and the lymphatic particularly those located near the point of inoculation. The blood, however, does not contain a very great amount of the virus, as it requires a con siderable quantity, as much as 500 cubic centi meters (half a litre) to be inoculated applied to a scarified skin before it will cause a vaccine le sion. It has also been demonstrated to be pres ent in the lymphatic glands, but it is not constant. The specific agent is to be found in these tissues only during the febrile state. Immunity can be conferred on other animals by transfusion of the blood during the febrile stage, provided a large quantity be given. It has been frequently noted that a certain train of symptoms fre quently follow where vaccinations are done a second time. This is particularly so where the virus has been derived from calves. There is a local reaction at the point of inoculation which appears in about 24 hours after, the place becomes reddened and slightly elevated and is usually accompanied by an itching; there is a slight zone of congestion around it, and taken altogether, it has the appeafance of a true vac cination. It subsides in a day or so. This is not a vaccination as was once believed, but is due to a reaction known as "anaphylaxis.° It has nothing to do with the virus of vaccinia, but rather to the presence of the foreign protein of the calf serum or cells with which at some previous occasion the body cells have been sen sitized.