IMMUNITY FROM CONTAGIOUS DISEASES. 
BIB 
was, in so far as ability to guide the horse is concerned.” If Dr. 
Curtiss will consent to lay aside his dogmatic assertions for a 
moment and consider the, to him, apparently dry and uninteresting 
facts of the problem, I may once more be able to show how far 
astray even a philosopher may be led by trusting to a too super¬ 
ficial glance of a subject. Take the disease known as fowl 
cholera for example. The germs of this disease multiply so 
rapidly outside of the body that gallons of any nutritious liquid 
in which they are placed would be swarming with them within 
thirt} T -six hours. Still, inoculate a susceptible chicken weighing 
not over a pound, and it will be four to six days before the first 
signs of the disease appear. In other words, although the germs 
have found their way into the nutritive liquids of a susceptible 
organism, their multiplication has been checked in a remarkable 
manner by the influence of t the body protoplasm. If a sufficiently 
small quantity of the virus is used for the inoculation, the microbes 
are unable to multiply in the body at large, even after the period 
of incubation has passed, but their multiplication is confined to 
the locality in which they are introduced. Again, if the number 
of microbes introduced into the tissues is sufficiently small, say 
twenty-five or fifty, there is apparently no multiplication at all; 
the bird does not contract the disease, nor are there any signs of 
local irritation, although the cells have never before been sub¬ 
jected to the influence of the poison, and consequently have not 
acquired in that way any ability to resist it. Take one more fact; 
the germs of a contagious disease are unable to multiply in the 
liquids of an animal that has acquired insusceptibility, although 
they are placed directly within the blood or lymph channels. 
These phenomena are all of the same nature, and they demon¬ 
strate, each in its way, the same fact—viz., that the protoplasm 
of the living body has a means of combating microbes which is 
not physical, and that it exerts this influence over the fluid which 
surrounds it to a considerable distance beyond the layer that is in 
actual contact with it. 
These facts are evidently very intimately connected with the 
question of immunity, and any theory which attempts to explain 
immunity must not only show how the cells acquire the power to 
