May 3, 1901.] 
slowly, that it did not reach Western Eu- 
rope until 1718, when Lady Mary Wortley 
Montagu introduced the process then in 
vogue in Constantinople. While the year 
1718 marks the introduction of protective 
inoculation to the aristocracy of England, 
the practice had come into use among 
Scotch and Welsh peasants at a much 
earlier date, which probably accounts for 
the next stage in the evolution of measures 
of protection against infectious diseases. 
Herdsmen and milkmaids in both Eng- 
land and Schleswig-Holstein observed that 
occasionally on the udder of cows there 
appeared an eruption resembling smallpox; 
that this eruption could be communicated 
to persons engaged in milking; and that 
persons infected with the cowpox were pro- 
tected against an invasion of true smallpox. 
The fact that the notorious Mrs. Palmer, 
Duchess of Cleveland, was thus protected 
is evidence sufficient to show that such ob- 
servations were common as early as 1663. 
In 1768 Fewster and Sutton in London ; 
1774, Jesty, a Dorsetshire farmer ; 1791, 
Pless, a Holstein teacher, and May 14, 
1796, Jenner, confirmed these observations. 
It is true that the immortal work of Jen- 
ner began as early as the year 1769; for at 
this time, while a student under John 
Hunter, he heard a young country woman, 
in whose presence the subject of small- 
pox was mentioned, say: ‘‘I cannot take 
that disease, for I have had cowpox.”’ 
Upon mentioning the subject to his master, 
Hunter replied “ Do not think, but try ; be pa- 
tient, be accurate.’ Jenner did try; was 
patient, was accurate; and on May 14, 
1796, after years of patient labor, in his 
‘Inquiry into the Causes and Effects of the 
Variole Vaccine,’ he experimentally estab- 
lished the following facts : 
1. That this disease (cowpox) casually communi- 
cated to man has the power of rendering him unsus- 
ceptible of smallpox. 
2. That the specific cowpox alone, and not other 
SCIENCE. 
685 
eruptions affecting the cow, which might be con- 
founded with it, had this protective power. 
3. That the cowpox might be communicated at will 
from the cow to man by the hand of the surgeon, 
whenever the requisite opportunity existed. And 
4. That the cowpox once ingrafted on the human 
subject, might be continued from individual to indi- 
vidual by successive transmissions, conferring on each 
the same immunity from smallpox as was enjoyed 
by the one first infected direct from the cow. 
Thus it is seen that Jenner, by inoculat- 
ing a cow with variolus matter produced 
in the cow an eruptive disease resembling 
smallpox, but of a milder type, and that 
the cultivation of this milder disease in the 
cow yielded a fixed virus (vaccine) which, 
transplanted to man, gave rise to a still 
milder eruptive disease (vaccinia) possess- 
ing constant characteristics, and conferring 
upon persons who underwent it immunity 
against smallpox. 
The older methods of inoculation against 
smallpox were quickly supplanted by the 
simpler and far safer method of vaccina- 
tion ; and since the introduction of the 
latter the appalling ravages of smallpox 
have been relegated to historical literature. 
The subsequent development of vaccina- 
tion is a matter of such general information 
that there is no need of its further discussion 
here. It is sufficient to say that in the 
great majority (if not in all) of the cases 
of successful vaccination immunity against 
smallpox is conferred for an indefinite 
period, varying from three years to many 
years—averaging three to seven years—in 
some cases for life; and that compulsory 
vaccination and revaccination offer the 
safest and surest protection against this 
loathsome disease. 
The success of vaccination gave great im- 
petus to the investigation of the problem of 
immunity, and the annals of the nineteenth 
century contain a voluminous record of the 
prolonged and patient efforts of a host of 
brilliant workers whose contributions have 
at least laid the foundation upon which the 
