Bacteria 
Nor are the other live cells of our body mere passive 
spectators of the prowess of their police phagocytes. 
They do what they can and secrete mysterious sub- 
stances called opsonins, which somehow paralyse or 
entangle the Bacillus so that it falls a helpless prey to 
the ‘“polymorphonuclear leucocyte,” which is the correct 
style and designation of the phagocyte.® 
Not only so, but those tissues which are set apart 
for the production and formation of phagocytes, work 
more energetically when a bacillus invasion is proceed- 
ing and turn out a much larger number of phagocytes 
than usual. 
There is a strange difference between individuals in 
these matters. The bodies of certain people are rich 
in opsonins, so that they are well able to resist bacteria, 
whilst others are decidedly feeble and weak “ opsoni- 
cally.” The researches of Messrs, Leishman and Wright 
must be consulted for further details as to the “ opsonic 
index,” &c. 
There are several methods by which people can be 
made immune to some particular infectious bacterium. 
One ingenious method consists in first isolating your 
race of bacteria and then turning that race into a feeble 
and inefficient variety, which will do no great harm to 
the individual but yet prevent any subsequent accidental 
invasion of the original wild bacterium from establishing 
itself. 
Such a wild germ would find the food material 
exhausted and the ground poisoned by the feeble race 
which preceded it, 
Pasteur’s method with the germ of hydrophobia 
consisted in exposing the colonies for a greater or less 
period to acurrent of air. The results of his experi- 
ments are quite remarkable, 
Before 1886, 16 per cent. of all persons bitten by 
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