8 Transactions Texas Academy of Science. 
rial from smallpox pustules was blown into the nostrils of persons 
who had not experienced an attack of the disease, that the disease 
in persons thus infected underwent a milder course, was accom- 
panied by a lower death rate, and conferred immunity against fur- 
ther attacks of smallpox. This early method of protection against 
the ravages of the disease became a common custom in China and 
India ; but was later superseded by a more direct method of inocu- 
lation — that of introducing beneath the skin the scab of variolus 
pustules. The Chinese used the dried scab, the ordinary Hindoos 
the fluid pus, and the Brahmans pus that had been kept in wool 
for a period of twelve months. The latter is clearly an instance of 
using attenuated virus. 
It should be remembered that smallpox extended westward to 
Europe during the sixth century, that it reached England toward 
the close of the ninth century, and at the time of the Crusades 
became widespread. In 1517 it was carried from Europe to Santo 
Domingo; reached Mexico in 1520, whence it spread throughout 
the Hew World. It was introduced into Iceland in 1707, and to 
Greenland in 1733. 
It should be particularly noted, that in the invasion of new ter- 
ritory the virulence of smallpox at once became greatly intensified — 
in some instances nearly one-half the population being destroyed 
by it. Robertson records the death of three million and a half of 
people in Mexico alone as the result of the invasion of 1520. Again, 
the ; dark colored races seem to be more easily infected than Euro- 
peans. 
The protective method of directly inoculating the pulverized 
variolus scab beneath the skin slowly traveled westward ; so slowly, 
that it did not reach Western Europe until 1718, when Lady Mary 
Wortley Montagu introduced the process then in vogue in Constan- 
tinople. While the year 1718 marks the introduction of protective 
inoculation to the aristocracy of England, the practice had oome t 
into use among Scotch and Welch 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 milk-maids in both England and Schleswig-Hol- 
stein observed that occasionally on the udder of cows there appeared 
an eruption resembling smallpox; that this eruption could be com- 
municated to persons in milking ; and that persons infected with the 
cowpox were protected 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 observations 
were common as early as 1663. In 1768 Fewster and Sutton in 
