Vaccination and inoculation have saved thousands of lives. Smallpox, once more prevalent than measles, was the scourge of Europe until vaccination was introduced. During the 18th century it was estimated that 60,000,000 people died of it, and at the beginning of the 19th century one-fifth of all children born died of smallpox before they were 10 years old. In countries where vaccination is not practised the disease is as serious as ever; in Russia during the five years from 1893-97, 275,502 persons died of smallpox, while in Germany where vaccination is compulsory, only 8 people died of it during the year 1897. Death rates from diphtheria and typhoid fever have been greatly reduced by the use of antitoxin and antityphoid vaccine. Thus in New York State in 1894, before antitoxin was generally used, 99 out of every 100,000 of the population died of diphtheria, while only 20 out of 100,000 died of it in 1914. In 1911 a United States Army Division of more than 12,000 men camped at San Antonio, Texas, for four months. All of these men were vaccinated against typhoid fever and only a single case occurred during the summer, although conditions of camp life always tend to spread the disease. While many and various factors tend to lower resistance rather than to increase it, the idea that these factors act equally in all kinds of infection is erroneous. "The principal causes which diminish resistance to infection are: wet and cold, fatigue, insufficient or unsuitable food, vitiated atmosphere, insufficient sleep and rest, worry, and excesses of all kinds. The mechanism by which these varying conditions lower our immunity must receive our attention, for they are of the greatest importance in preventive medicine. It is a matter of common observation that exposure to wet and cold or sudden changes of temperature, overwork, worry, stale air, poor food, etc., make us more liable to contract certain diseases. The tuberculosis propaganda that has been spread broadcast with such energy and good effect has taught the value of fresh air and sunshine, good food, and rest in increasing our resistance to this infection.