It has been found from experience in hospitals that deaths from diphtheria are largely preventable by _early use_ of antitoxin. When antitoxin was used on the first day of the disease no deaths took place. If not used until the second day, 5 deaths occurred in every hundred cases, on the third day 11 deaths, on the 4th day 19 deaths, and on the 5th day 20 deaths out of every hundred cases. It is therefore advisable, in a suspected case of diphtheria, to have antitoxin used at once to prevent serious results. Vaccination.--Smallpox was once the most feared disease in this country; 95 per cent of all people suffered from it. As late as 1898, over 50,000 persons lost their lives annually in Russia from this disease. It is probably not caused by bacteria, but by a tiny animal parasite. Smallpox has been brought under absolute control by vaccination,--the inoculation of man with the substance (called _virus_) which causes cowpox in a cow. Cowpox is like a mild form of smallpox, and the introduction of this virus gives complete immunity to smallpox for several years after vaccination. This immunity is caused by the formation of a germicidal substance in the blood, due to the introduction of the virus. Another function of the board of health is the preparation and distribution of vaccine (material containing the virus of cowpox). Rabies (Hydrophobia).--This disease, which is believed to be caused by a protozoan parasite, is communicated from one dog to another in the saliva by biting. In a similar manner it is transferred to man. The great French bacteriologist, Louis Pasteur, discovered a method of treating this disease so that when taken early at the time of the entry of the germ into the body of man, the disease can be prevented. In some large cities (among them New York) the board of health has established a laboratory where free treatment is given to all persons bitten by dogs suspected of having rabies. Vaccination against Typhoid.--Typhoid fever has within the past five years received a new check from vaccination which has been introduced into our army and which is being used with good effect by the health departments of several large cities. The following figures show the differences between number of cases and mortality in the army in 1898 during the war with Spain and in 1911 during the concentration of certain of our troops at San Antonio, Texas. 1898--2nd Division, 7th Army Corps, Jacksonville, Florida. June-October, 1898 Mean strength, 10,759. Cases of typhoid certain and probable, 2693. Death from typhoid, 258. Death from all diseases, 281. Manoeuver Division, San Antonio, Texas. March 10-July 11, 1911. Mean strength, 12,801. Cases of typhoid, 1. Death from typhoid, 0. Deaths all diseases, 11. [Illustration: Comparison of cases of and death from typhoid in 1898 and 1911. What have we learned about combating typhoid since 1898?]