THE STRUGGLE FOR LIFE. 223 
two animals, the one protected, and the other not protected 
by the injection of this serum. 
It is on these facts that the modern treatment of some 
of the terrible diseases to which the human body is lable, 
by the injection of serum containing the appropriate anti- 
toxine, is based, the serum being taken from the veins of 
an animal artificially rendered immune to that disease. 
Jenner, long ago, by the patient observation of facts, 
learnt that the development of the vaccine vesicle in any 
individual, rendered his tissues unfit to propagate small-pox, 
but he was quite ignorant of the reason. With the modern 
methods of the treatment of these diseases, the name of 
Louis Pasteur is inseparably linked. He proved, that by 
systematic injection of artificially weakened cultivations of 
the Bacillus of Hydrophobia, during the stage of incubation 
in the body, the mortality might be reduced to something 
very small indeed, a discovery fraught with untold blessings 
to humanity! Now that it has been proved that immunised 
serum is efficacious for the treatment, among other things, 
of Hydrophobia, Lock-jaw, and probably of Diphtheria, new 
paths of knowledge have been opened up, and no one yet 
knows, what in the future, may be the use found for 
materials elaborated in Nature’s living laboratory in the 
treatment of disease, since we have as yet, hardly passed 
over the threshold of these investigations. 
Before I conclude, I might just mention one other fact, 
which is at the least quite as mysterious as anything I 
have yet mentioned. It is this: if there be an overgrowth 
of any particular tissue, as of the fat for example, and if 
this occurs in a position where the fat normally is found, 
although it may form an enormous tumour, it will do no 
particular harm, except perhaps by the pressure exercised 
by its bulk, and by the undue amount of nourishment 
diverted from other parts of the body. But if cells belong- 
ing to one tissue gain entrance to, and take root in, another 
