28 VACCINATION resist the various noxious influences by which the age of infancy, especially among the poor, is beset. The value of cowpox as a protection against smallpox may now be judged of apart from the fanciful doctrine of variolse vaccinse by which it was originally recommended. It has been put to a test extending over eighty years ; and in some circumstances it has been possible to apply the logical methods of agreement and differ ence with a good deal of cogency. The besetting fallacy of all vaccination logic is that of post hoc ergo propter hoc ; and the only way to escape it is to hold intelligent views of the history, the natural history, and the epidemiology of smallpox. This will ne cessitate a brief excursus. Small- Smallpox, which is really a tropical skin disease of the nature of pox. lichen turned pustular, or of ecthyma, must be judged according to what we know of foreign pestilences in general. Perhaps we are safest to take a line through the behaviour of the plague. Plague in western Europe had the start of smallpox by a good many years, if we speak only of prevalence on the large scale. " Throughout the 16th century," says Hirsch, "the plague was a permanent form of disease on the continent of Europe. . . . During the first two- thirds of the 17th century we still meet with it over an equally wide area and equally often. But in the last thirty years of that century the plague was observed to be retreating gradually from the soil of Europe." It was not only in London after the fire of 1666 but also in Denmark and Sweden, in Italy, in Holland and Belgium, in Switzerland, in France, in western Germany, and in Spain that the years 1660-1680 saw the last of plague ; it lingered only in the Levant, in Poland, and in other parts of north-eastern Europe, with occasional epidemic visits, such as those of Messina and Mar seilles. Now it has left the Levant and Egypt, has abandoned even Mesopotamia and Arabia, and retreated to a few poor villages on the Perso-Armenian frontier. Or, take the example of leprosy, which owed its existence rather to the widespread or national con currence of the same causes in various countries than to the travel ling of an infection : Italy had it first and lost it first, and nearly every other country in Europe saw its rise, its general prevalence, its decline, and its extinction, the northern countries keeping it longest. Again, typhus fever was a standing disease so long as Europe was the theatre of protracted wars and all their consequences ; but, like other infections, typhus gradually declined and has almost disappeared since the conditions on which it depended ceased. Leaving these parallels and coming to the facts of smallpox itself, it rose to prominence in western Europe in the 16th century, and in England in the 17th. 1 From the early part of the 18th century a remission was noted ; but the latter half of that century saw a considerable extension of the area of the disease, for which the practice of inoculation has been blamed. It is a mistake to suppose that smallpox has shown a tendency towards a universal infection ; for all its chances it has kept within moderate limits of age and place, and extended only by repeated provocation. Thus, Hirsch says of the western hemisphere, "A still more terrible source for America was the importation of Negro slaves, so much so that in after years, particularly in South America and the West Indies, not only the first appearances of smallpox, but every fresh outbreak of it, could be traced to importation from Africa," the African continent being then, as now and always, one of its principal native seats. In Europe it has been peculiarly a disease of infancy and of the most crowded parts of cities. It has had victims among the upper classes, just as cholera has had ; but, like that disease, its habitat is among the crowded poor ; and it would have touched the well- to-do-classes less in former times if there had always been spacious west-end quarters in cities or the modern "passion for clean linen," personal ablutions, and fresh air. Tenement houses and ill- ventilated courts or alleys have been the natural harbourage of smallpox ; in proportion as these have been demolished the disease has disappeared or been circumscribed in its area. It is fallacious to estimate its prevalence now in ratio of the whole population ; for a just comparison of one period with another, we have to take into account, not the death-rate per million living, but the death-rate per million still living under the old-world conditions. From the earliest period of its history in Europe, the disease has had its seasons of quickening or revival, with long intervals of quiescence ; only in the most crowded parts of Western cities has it ever been endemic from year to year. These epidemic outbursts have varied much in intensity and in area, the conditions of variation being mostly unknown. In that respect, it need hardly be said, small pox is like other epidemic diseases. nfluence During the early years of the 19th century there was a marked f yacci- remission of the epidemic outbursts of the disease in most parts of
- ation Europe. The amount of vaccination during those years was in-
millnn The first known nse nf the term " small pocks " is in Holinshed s Chronicle >UA - (1577), an epidemic of pestis in 1365 being so rendered, although it was prob ably the ordinary bubo-plague of the period. The pox of Elizabethan writers was the French pox or great pox (syphilis), which overran Europe as an epi demic in 1404. Its prominent character at its first appearance was the loath some affection of the skin (especially the face) ; hence when variola came on the scene it was called the lesser pox, or smallpox. considerable ; in particular it hardly touched the poor. Thus, at the time of the Norwich epidemic of 1819, it was estimated (by Cross) that only one-fourth of the inhabitants were vaccinated, and these almost exclusively the well-to-do. At the same time the practice of inoculating smallpox, which was with good reason blamed for keeping the contagion generally diffused and active among the non-inoculated, began to be discontinued and soon ceased altogether. Undoubtedly there was a marked decline in smallpox during the first fifteen years of the century, but the as sociated circumstances are as complex as the fact itself is simple. We have to bear in mind the old law of periodic exacerbation and dormancy, the cessation of a practice (inoculation) which almost certainly interfered with the natural tendency of smallpox as a foreign pestilence to die out, and the unusual prevalence of typhus fever (on the Continent), and other displacing or substitutive factors in the death-rate. To what extent vaccination was a factor will have to be decided by the experience of a period when the practice was much more generally in vogue. For that purpose we may here restrict the inquiry to England and Wales, premising that the experience of other European countries where vaccination has been equally practised is not different. The following table (III.) begins with the year 1847 ; the re gistration reports go back to 1838, but there is a" break in the tables for five years near the beginning. Deaths from Smallpox from 1847 to 1884, with the numbers among Children under five. Year. Total of All Ages. Children under Five. All Other Ages. Year. Total of All Ages. Children under Five. All Other Ages. 1847 4227 3114 1113 1866 3029 1662 1367 1848 6903 4782 2121 1867 2513 1370 1143 1849 4644 3146 1498 1868 2052 1234 818 1850 4665 3265 1400 1869 1565 892 673 1851 6997 4869 2128 1870 2620 1245 1375 21852 7320 5076 ?A4 1871 33126 7770 15356 1853 3151 2164 987 1872 19094 5758 13336 1854 2808 1659 1149 1873 2364 587 1777 1855 2525 1323 1202 1874 2162 543 1619 1856 2277 1299 978 1875 950 271 679 1857 3936 2335 1601 187C 2408 612 1796 1858 6460 8585 2875 1877 1,278 1056 1859 3848 2247 1601 1878 1856 472 1384 1860 2749 1544 1205 1879 536 130 406 1861 1320 723 597 1880 648 170 478 1862 1628 931 697 1881 3038 740 2358 1863 5964 3267 2697 1882 1317 275 1042 18Gk 76S4 A^.94 3390 1883 957 226 731 1865 6411 3262 3149 1884 2234 503 1731 In the first years of the table the deaths from smallpox of children under five were to those of all other ages in the ratio of 3 to 1 or of 5 to 2 (at Norwich in 1819 there were 530 deaths, of which half were in infants under two, and all the rest save ten were in children under ten years) ; the disproportion lessened gradually, until about 1864 it was nearly 4 to 3 ; in 1870 the proportion was nearly equal ; and from that time onward the preponderance leaves the age of infancy and childhood, so that in 1884 the deaths under five were three times fewer than those at all other ages. The great epidemic of 1871-72 brought out that remarkable change of incidence most decidedly. Taking the mortality of 1871 as an instance, the signi ficance of the changed incidence on the periods of life is that the 7770 deaths under the age of five would, in pre-compulsion times, have had a complement of no more than 2500 deaths in the later periods of life, or that the actual mortality of 15,356 above the age of five would have had a complement of some 40,000 or 45,000 deaths below that age. (In British India in 1884 of 333,000 deaths 72 per cent, were of children under 12 in Bengal, and 64 per cent. in Madras.) Apart from the changed incidence of smallpox, Table III. shows merely the caprices of the disease as an epidemic. After every epidemic outburst the disease declines and sometimes looks as if it were about to die out altogether. The alarm attending each severe epidemic has induced the legislature to make the vac cination law more stringent and vaccinators to insert more of the virus, so that the periodic subsidence has corresponded to, and has seemed to be owing to, the better enforcement of the practice ; but there have always been alternating periods of quiescence and ex acerbation, irrespective of any prophylactic. Moreover, smallpox being a foreign contagious skin disease lurking in congenial haunts, it would be quite according to precedent that it should one day cease absolutely in a community where sanitary progress had ad vanced so far as to take the ground from under the feet of the pestilence ; such absolute cessation would have no more necessary connexion with almost universal vaccination than the alternating quiescence and recrudescence of epidemics have been connected with each new Act of Parliament. The epidemic of 1871-72 was one of the worst in the whole history of European smallpox ; and it may be that_ it was one of the last flickers of a slowly expiring flame. The universal practice of cowpoxing, however, is based upon the
2 The Italic numerals indicate the periodic maxima.