10 THE PRESIDENTIAL ADDRESS. 
given, roughly speaking nine or ten out of every thousand wounded were 
attacked by tetanus and some 85 per cent. of these died. 
After the anti-tetanic injections had been introduced the incidence 
fell to little more than one per thousand, and the mortality to less 
than half. 
To put the matter broadly: during the war there were 2,500 cases 
of tetanus in the British Army, with 550 deaths. If there had been no 
prophylactic injection of anti-tetanic serum there would probably have 
been 25,000 cases with 20,000 deaths—a very striking example of the 
recent development in the prevention of disease. 
Another very important and widespread disease, somewhat resembling 
tetanus, is diphtheria, and there is no better example of the advance of 
science in methods of cure and prevention than is found in this 
disease. 
Thanks to the work of Klebs and Léffler in the early eighties and, some 
years later, to the brilliant researches of Roux and Yersin, the causation 
and natural history of this disease were very thoroughly elucidated. 
Anti-diphtheritic serum is prepared much in the same way as the anti- 
tetanic. By the repeated injections of gradually increasing doses of the 
bacilli or their toxins, a serum is produced which has a marked curative 
effect in cases of diphtheria. 
It is stated that the introduction of anti-diphtheritic serum in 1894 
has reduced the death-rate from 40 to 10 per cent., and if used on the first 
day of the disease to almost nil. 
The serum is essentially a curative agent and is useful only to a limited 
extent in prevention. 
But lately essentially preventive measures in diphtheria have come into 
vogue. The procedure employed is to bring about an active immunisation 
by a mixture of toxin and antitoxin in individuals who have been shown 
to be susceptible to the disease by what is known as the Schick test. 
In the United States a campaign on these lines has been begun against 
this disease which promises brilliant results. It is confidently stated that 
by their new measures there is a possibility of robbing diphtheria of all its 
powers to kill or injure. 
The mode of prevention of these diseases—Malta fever, typhoid fever, 
and tetanus—illustrates the three principal methods of preventing bacterial 
diseases : in Malta fever, by getting down to bed-rock and stopping the 
disease at its source ; in typhoid fever, by giving, as it were, a mild attack of 
the disease, by vaccination or inoculation, so as to bring about a greater 
