BACTERIOLOGY AND THE WAR. 19 
bacteria. Very extensive researches are, however, being made 
into this question, notably under the direction of the Medical 
Research Committee, and a new antiseptic, Eusol, i.e., hypo- 
chlorous acid, made from bleaching powder, has recently 
been introduced, which seems to be the most satisfactory 
that has yet been devised. 
Another new method, devised by Sir A. E. Wright, of 
treating badly-infected wounds is to wash them with solutions 
of harmless salts which draw out from the blood extra quantities 
of phagocytes and plasma to destroy the bacteria and their 
toxins. 
Protection Acarinst Micropic Diskases By MEANS oF 
VACCINES AND SERA. 
I have already described Nature’s methods of defending 
the body against the attacks of bacteria. Let us next consider, 
very briefly, how the application of these and other principles 
has led bacteriologists to devise new methods to assist Nature. 
I will mention two: first, the use of vaccines, the best known 
being typhoid vaccine; second, the use of sera, the best 
known being diphtheria antitoxin. 
In ‘order to understand the principles at work I must 
allude to ammumty. Immunity means a complete or partial 
resistance to a particular microbe. It may be inherited by 
nature or subsequently acquired by training, e.g., man is by 
nature completely resistant to distemper, but not to plague 
or typhoid. On the other hand, dogs are by nature resistant 
to typhoid but not to distemper. 
Both men and animals, however, can be trained by Nature 
to acquire considerable resistance to some microbic diseases 
to which they are susceptible, by a single non-fatal attack. 
Consequently, second attacks of typhoid or plague are rare in 
man, and of anthrax rare in cattle. The recovery and subsequent 
