By these tables [wrote Dr. Jurin] it appears that upwards of 7 per cent., or somewhat more than a fourteenth part of mankind, die of the smallpox; and consequently the hazard of dying of that distemper, to every individual born into the world, is at least that of 1 in 14.[33]
This large induction from London to universal mankind is noteworthy, because, as we shall see, it came to be often made, and involved a serious fallacy; for unless universal mankind dwelt in conditions similar to Londoners, it was idle to infer a common rate of disease and mortality. The population of London in 1701 was estimated at about 500,000 (there was no exact census), rising to about 600,000 in 1720. It was closely packed and lodged over cess-pools; the water supply was insufficient, and there was no effective drainage. The vast multitude was disposed, as if by design, for the generation and propagation of zymotic disease, and specially smallpox. Little attention was paid to personal cleanliness, and still less to ventilation, to light, to exercise. The condition of a large urban community a century ago is almost inconceivable at the present day. Londoners were then only slowly and blindly rising out of those modes of existence which made the Plague of 1665, and other plagues, possible. Hence we need not be astonished that smallpox was a common and persistent affliction; but it was less prevalent and less deadly than it is the custom to assert; and had the disease not been attended with injury to feminine beauty, there might have been no more fuss made about it than about any other form of eruptive fever.
It has also to be observed, that smallpox as a cause of death was probably much exaggerated in the Bills of Mortality; for as Isaac Massey pointed out—
These Bills are founded on the ignorance or skill of old women, who are the searchers in every parish, and their reports (very often what they are bid to say) must necessarily be very erroneous. Many distempers which prove mortal, are mistaken for the smallpox, namely, scarlet and malignant fevers with eruptions, swinepox, measles, St. Anthony’s fire, and such like appearances, which if they destroy in three or four days (as frequently happeneth) the distemper can only be guessed at, yet is generally put down by the searchers as smallpox, especially if they are told the deceased never had them.[34]
Massey, in the same spirit of good sense, objected to generalisations about smallpox from the Bills of Mortality, as if all who died were slain by the disease and by nothing else.
There ought to be no comparison [he said] between sick people, well regimented with diet and medicine, and those who have no assistance, or scarcely the necessaries of life.
The miserable poor and parish children make up a great part, at least one-half of the Bills of Mortality; to confirm this I have examined several yearly bills, and I find that the out-parishes generally bury more than the ninety-seven parishes within the walls, and the parish of Stepney singly, very near as many as the City of London yearly; this sufficiently shows what little help and care are taken of the poor sick, which so much abound in all those places.[35]
Of course there lurks a fallacy in all statistics of disease wherein conditions of life are not discriminated. Whether patients survive or die from any zymotic ailment depends upon their breed, their circumstances, their habits, and their medical treatment and nursing—all essential particulars, yet difficult to define and register on a large scale. It would appear that in sound constitutions, and with fair treatment, smallpox in 1721 was by no means deadly, whilst in bad constitutions, and with exposure and neglect, it was extensively fatal. Yet of these differences, little account was taken by the Inoculators, and the malady was measured and discussed as though it were something uniform like water or gold. Massey in one year had 49 cases of smallpox and one death; in Stepney an equal number of cases might have shown a mortality of 20 or 30 per cent.; whilst Dr. Nettleton reported that of 1245 cases in Halifax and adjacent towns in Yorkshire, there died 270, or about 22 per cent.[36]
One of Massey’s fears in relation to inoculation was the risk of poisoning the blood with more than smallpox. He was not disinclined to experiment with “duly prepared children infected with smallpox by inspiration,” for then—
They will run no hazard of being infected by a leprous, venereal, or scrofulous taint that may, for aught we know, be transplanted by inoculation.[37]