Jenner’s originality consisted in boldly designating cowpox as variolae vaccinae or smallpox of the cow, and in tracing cowpox itself back to the grease of the horse’s hocks. The latter contention was at length set aside by practical men as a crude fancy; the former designation is just as arbitrary and untenable. It was elaborately shown by Pearson in 1802, and has often been confirmed by subsequent writers, that the vesicle of inoculated cowpox, even while it remains a vesicle, is quite unlike a single pustule of smallpox. But it is only for the vesicular stage of cowpox that there is even an allegation of likeness to variola; the vesicle of natural or unmodified cowpox is only the stage of the disease before it becomes an ulcer, either inflammatory or indurated. Inoculated horse grease has the same vesicular stage; and so also has the venereal pox when it is inoculated experimentally on the skin. These three very different infections have the same kind of vesicle, in every case unlike a smallpox pustule, and the same natural termination in a phagedenic or indurated sore.

Jenner’s originality in starting vaccination in practice is for the most part misunderstood. When he published his Inquiry in June 1798, he had twice succeeded in raising vaccine vesicles by experiment,—the first time in 1796 with matter from a milker’s accidental sore, and the second time in March 1798 with matter direct from the cow. The first experiment was not carried beyond one remove from the cow; the second was carried to the fifth remove, when the succession failed. A third experiment, in the summer of 1798, failed from the outset; and his fourth and last experiment, in November-December 1798, led to nothing but extensive phagedenic ulceration in two cases out of six vaccinated.

In this posture of affairs Woodville of the inoculation hospital, London, succeeded in January 1799 in starting a succession of arm-to-arm vaccinations from a London cow, which were exceptionally free from the ulcerative termination. From that source Jenner himself was supplied with lymph in February, while more than two hundred practitioners both at home and abroad were supplied some three weeks later. There was a quarrel with Woodville in due course, and an attempt to set up an authentic Jennerian lymph independent of the London stock. But the merits of this claim (which otherwise rests on the vague evidence of Marshall) may be judged of by the fact that Ring’s application to Jenner in September 1799 for genuine lymph was answered by the latter with a supply of matter which was none other than Woodville’s own stock, after six months’ use in the country. Woodville’s stock was used all over the world down to 1836. By that time there were numerous complaints that the lymph was degenerating, and a widespread feeling that it was necessary to “go back to the cow.” Apart from the numerous original cases of cowpox alleged to have been found in Würtemberg, the first new authentic source was the Passy cow of 1836. From the accidental vesicles on the milker’s hand Bousquet, the director of vaccination in Paris, started a new stock, which partly superseded Woodville’s lymph hitherto in use in France. In 1838 Estlin of Bristol, after several years’ vain endeavours, heard of original cowpox in Jenner’s own parish of Berkeley (Gloucestershire), where the disease was so far forgotten that the milkers were for several days unaware that the vesicles on their hands had been contracted from cows. Estlin’s new geniture is one of the most fully recorded in the history of vaccination. In the same year, and the two following years (1838-41), Ceely of Aylesbury found some half-dozen distinct occurrences of cowpox in the dairy-farms of his district, and cultivated lymph from them. His account of the natural history of cowpox in the cow, and of the effects of primary lymph when inoculated on the human arm, is by far the most comprehensive and candid that has ever been given; without it we should hardly have understood the real nature of cowpox. Bousquet, Estlin, and Ceely are the chief writers who have authentically described the establishment of new stocks of cowpox lymph since Woodville’s original report of 1799. There are numerous other references, less detailed, to original cowpox in the cow, and to vaccinations therefrom, in England, on the Continent, and in the United States; some of these came to light in the inquiry of the Epidemiological Society in 1852. One of the best-known cases of comparatively recent times is the Beaugency cow of 1866, which has been the source of much of the calf-lymph of the Dutch, Belgian, and other vaccine “farms.” Another French case occurred in the Gironde in November 1881, and is described in the Bulletin of the Academy of Medicine (p. 17, 1882). In England the editors of the Veterinarian inserted a notice in the number for August 1879, making a request to their readers for lymph “from vesicles on the teats of cows in cases of so-called natural cowpox.” The only answer to it hitherto has been an intimation in June 1880 that there was a case of cowpox at Halstead in Essex, which was visited by Ceely and others and pronounced by the former to be of the nature of eczema. In 18/6 the disease was found at a farm near Reykjavik in Iceland, where it had never been seen before; it was of the old type, producing sores on the milkers’ hands, and causing much alarm by its unfamiliar character.

The so-called calf lymph is as remote from the cow as ordinary humanized lymph; it differs from the latter merely in the circumstance that the calf (on its shaven belly) becomes the vaccinifer, instead of the child, and that the cycle of the disease is very much abbreviated or contracted in the calf: the vesicles are distended with lymph about the fourth or fifth day, instead of the seventh or eighth, and are almost unattended by areolar redness and constitutional disturbance, the animal being able to support fifty to a hundred or more vesicles without the smallest inconvenience. On the child’s arm the vesicles after calf-lymph are slower in development than in the calf, and are attended by areola, &c.

Under the influence of theory, “vaccine” lymph has been got from two sources that have absolutely nothing to do with cowpox; and, oddly enough, the matter from these sources has been so managed as to produce correct vesicles on the child’s arm. One source is the grease of the horse’s hocks and the other is smallpox itself.

The grease of the horse was known to produce vesicles and subsequent ulcers on the hands almost indistinguishable from those of accidental cowpox. There was also the tradition (which breaks down when tested by facts) that accidental infection with the grease protected from smallpox. Jenner held that all “genuine” cowpox came from horse-grease; and, after he had raised vaccine vesicles on the arms of children by matter from the cow’s teats, he proceeded to try whether he could not raise the same kind of vesicle experimentally by matter once removed from the horse’s hocks. The experiment succeeded, just as the accident had done. The vesicle (represented in plate 2 of the Inquiry) ulcerated, and the boy died of what is vaguely termed a “fever” in one place and a “contagious fever” in another. The same kind of inconsequent logic suggested the experiment of inoculating the matter of horse-grease upon the skin of the cow’s teats, the object being to prove the identity of cowpox with the grease. That too succeeded in the hands of Loy of Whitby. Loy also inoculated children with the same matter, and raised vesicles on their arms, which were, of course, the same as the accidental vesicles (compared to the blister raised by a burn). Sacco of Milan actually used the equine matter on a large scale, instead of cowpox matter; and De Carro of Vienna " equinated” many persons in that city with lymph sent him by Sacco. Baron prints a memorandum of Jenner, dated 23d July 1813, relating to “equine virus which I have been using from arm to arm for these two months past, without observing the smallest deviation in the progress and appearance of the pustules from those produced by vaccine,” and a second note, dated 17th May 1817, in which Jenner says he “took matter from Jane King (equine direct) for the National Vaccine Establishment. The pustules beautifully correct.” This is not the place to enter upon the pathology of horsegrease; and, as a matter of fact, equination has not been much practised on the whole. According to Jenner’s own data, it was an occasional constitutional disease of the horse’s hocks in wet seasons, which was communicable to the hands of men in the form of large whitish vesicles, ending in corroding and painful open sores (see the case reported to him by Fewster, op. cit., ed. 1800, p. 96).

The other anomalous source of “vaccine” is human smallpox. Jenner having succeeded in passing off his doctrine that cowpox is smallpox of the cow, it occurred to some persons about forty years after to prove the doctrine by experiment, the proof being to variolate the cow on the udder. This was accomplished in 1838, after much trouble, by Thiele in Kazan (Russia), who inoculated several thousands of persons with the variolous matter “passed through the system of the cow.” Within a few months of that experiment, the same thing was attempted by Ceely of Aylesbury, who succeeded, after many failures, in raising a large variolous pock, not on the udder of the cow, but on the mucous membrane of the vulva. The first experiment with the matter of this pock was undesigned; his assistant pricked his hand with the lancet which had just been dipped into the large pustule, and in due course had an attack of smallpox. Ceely persevered with his experiments (having meanwhile variolated another heifer at five places on the vulva), and in due time so “managed” his matter as to produce vesicles on the human arm (without general eruption on the skin), which were regarded at Cheltenham and other places as on the whole better than the cowpox vesicle of the period. But the real practical application of this idea was reserved for Badcock, a dispensing chemist at Brighton. It does not appear that any authentic or fully detailed account of Badcock’s experiments has been published; but he thus summarized the results some forty years later (Pall Mall Gazette, Jan. 23, 1880):—“By careful and repeated experiments 1 produced, by the inoculation of the cow with smallpox, a benign lymph of a non-infectious and highly protective character. My lymph has now been in use at Brighton for forty years, and is at the present time the principal stock of lymph employed there, being that exclusively used by the public vaccinators.” At Boston, U.S., the same kind of lymph was raised and put in use in 1852. But at Attleborough, Mass., the same experiment had in 1836 led to disaster. Smallpox was inoculated on a cow’s udder, and the product used to vaccinate about fifty persons. The result was an epidemic of smallpox, a panic, and the suspension of business. On the face of it this method was simply variolating the cow (on a mucous membrane if the hairless or shaven skin failed) and inoculating the human subject with that curiously disguised smallpox matter. However, it was thought necessary to hold an experimental inquiry upon it, and in 1865 a commission of the Lyons Society of Medicine reported that, “in vaccinating according to the method of Thiele and Ceely, we are merely practising the old inoculation, rendered uniformly benign, it may be, by the care taken to inoculate only the first product (l' accident primitif), but preserving for certain all its risks in respect to contagion.” A negative result was come to by Klein in 1879, in an inquiry for the Local Government Board, wherein he had Ceely’s cooperation. In 1879 the Irish Local Government Board prevented the use of similar variolous lymph by threatening to prosecute under the Act making the inoculation of smallpox penal. Notwithstanding the common sense of the case, and these experimental proofs, the official view taken by the medical department in 1857, that Thiele, Ceely, and Badcock had established the correctness of Jenner’s doctrine of variolae vaccinae, is still held very tenaciously by the profession. It is too simple and attractive to be soon given up; but perhaps the best way to get rid of it is to state in plain terms what cowpox itself really is.

Although there is no difficulty in drawing up a complete natural history of cowpox, thanks to the laborious and exact studies of Ceely, yet the attention has been so much diverted to side issues that the facts to be stated in this section will come before most readers with the aspect of novelty. The other original authorities besides Ceely are Jenner himself, Pearson (who collected information by circular in the months following Jenner’s Inquiry), Bousquet (1836), Estlin (1838), and Crookshank (1888). The Würtemberg inquiry, published by Hering (Stuttgart, 1839), is made up of very indifferently authenticated or incomplete statements, which have not the same value as the rest, and are at variance with them on the most essential points.

Cowpox as an infective disease arises in cow-houses here and there, and at wide intervals of time, out of a common physiological or constitutional eruption of some particular cow, usually a heifer in her first milk, very often in the spring season or at some other crisis of the year or of the animal’s life-history. It never arises except in milch cows; it occurs nowhere in the cow but on the teats, or, by infection, on adjoining parts of the udder. All the characters by which we know it distinctively as cowpox are associated with the fact of milking, or with the inevitable traction on teats that are the subject of an otherwise unimportant eruption. The primary disorder, as Ceely describes it, is an eruption of a few pimples, the size of a vetch or larger, hard and solid at first, but at length slightly vesiculated on the summit. It is only rarely that a series of events ensues on this basis which constitute cowpox as we know it; they ensue in some one animal out of many in the same byre, and years may elapse before the event happens again. The pimples on the teats are made to bleed by what Ceely calls “the merciless manipulations of the milkers”; the blood forms crusts, which are dislodged every six hours; and indurated ulcers form on the sites of the original pimples.

The process being thus made inveterate owing to the incessant interference of the milker’s hands, it becomes communicable to the other cows. The milkers can usually point out some one cow in which the disease began; and it spreads slowly through a byre, taking sometimes as long as three months to go the round of all the animals. An animal already infected at one or more places on its teats may become infected at other places on the teats and body of the udder, either by the traction of milking or by the contact of parts when the cow is lying down.

The ulcers heal sometimes slowly, sometimes more quickly; they may heal under crusts, or as open sores; induration and rounding of the edges are distinctive, along with much thickening of the base. The scars are also indurated, rounded arid elevated at the edges, and smooth or puckered on the surface; they are often as large as a walnut. It is not easy to see a vesicular stage of the disease even in the cows infected from the initial spontaneous case; and Ceely had for the most part to be content with the coagulated matter of crusts to vaccinate with. The process is, in fact, bound up from first to last in the most intimate and essential manner with the operation of milking. Cowpox “undisturbed by the milker’s hands” has no existence in the originating cow; it is the persistent irritation that makes it a pox. It is communicable, also, to the hands of the milkers themselves, and by their filthy hands to their faces. Jenner mentions a good many such cases; Pearson has collected several; and Ceely gives three in very full detail. As in the inoculated venereal pox, the infection proceeds for a time under the skin, making a bluish-white vesicle; it eats away the tissues round the margin, where the fluid makes the skin bulge out into the characteristic tumid ring. After the fourteenth day the vesicle will have become an eschar, the average size of a sixpenny piece, which comes away and leaves a sore. The open sore is a regular part of the infection in the milker’s hand. Various regions of the face get infected by contact from the hands: Jenner mentions the case of “a poor girl who produced an ulceration on her lip by frequently holding her finger to her mouth to cool the raging of a cowpox sore by blowing upon it”; another of Jenner’s cases had the sore on the wing of the nose; one of Ceely’s cases had an ulcer on the temple three-quarters of an inch long; in a case observed by Crookshank there was a very large vesicle and subsequent sore over the left cheek-bone. The local infection is accompanied by constitutional disturbance, more or less severe, including headache, pains in the loins, vomiting, and sometimes delirium. The axillary glands become painful, usually about the fourth day, and remain hard for some time. Eruptions occurred, but there is very little said about them.

As might have been expected, the effects of experimental infection with cowpox matter were the same as the accidental. They are spoken of as the effects of “primary lymph,” that is to say, lymph direct from the cow’s teats or from the milker’s sore hand, or in the earlier removes from these sources. Jenner’s experience of primary lymph was very much the same as Bousquet’s, Estlin’s, and Ceely’s forty years later. Woodville’s, on the other hand, was exceptionally reassuring; had it not been so, it is not likely that cowpoxing on the large scale would ever have survived the initial discouragements entailed by the use of primary lymph. The process on the child’s arm was on the whole the same as on the milker’s hand, allowing for the more deliberate mode of inoculation and for different texture of the skin. The vesicle grew to a great size up to the fourteenth day, and often became an ulcer, either excavated under the crust or absolutely open. Estlin did not entirely get rid of ulceration until after the twenty-ninth remove from the cow. The constitutional disturbance was often severe in infants: axillary tenderness and swelling were somewhat constant, and eruptions were especially frequent about the second to the fourth week, including macular roseola, lichen, and pemphigoid bullae. At each successive remove from the cow the cycle of the process became more contracted, and the constitutional disturbance, caeteris paribus, became less. Bousquet gives a plate which shows by parallel series of figures the differences between the vesicles of the old lymph (Woodville’s, nearly forty years old) and the lymph from the Passy cow. The new lymph induced a process more protracted at every stage: the vesicle continued to enlarge at the periphery for several days after the common vaccine vesicle of the period would have ceased to extend. It was not at its maximum until about the end of the second week, and it then became an eschar and a sore. Bousquet confesses that he first understood “les frayeurs de Jenner” when he saw the ulcerative and other effects of primary lymph. After a certain number of removes from the cow the cycle became so contracted that...