RESISTANCE AGAINST MICROORGANISMS. 255 
personal vigor will do more to ward" increasing, germ diseases than 
a relaxing of the rules which try to prevent the distribution of 
bacteria. Personal resistance of the individual will enable him to 
repel many an attack of disease bacteria, even if he has been directly 
exposed to them, while a weakened resisting power may result in 
his yielding to the first attack of an invading bacterium. For some 
of the less violent diseases (tuberculosis) this is much more emphatic- 
ally true than for other diseases (anthrax). Now, it is not possible 
to hope that we shall ever be able to exterminate all pathogenic 
bacteria; even if we did, other forms would doubtless take their 
places. Since we cannot exterminate them, it follows that all 
individuals will, at some time, be exposed to the attacks of some 
of the disease germs. Manifestly, then, the best means of elevating 
the healthfulness of the race is to raise the resisting power, at the 
same time doing our utmost to destroy pathogenic bacteria. 
These facts are equally true, whether we are dealing with animals 
or with man. It is of more importance for the farmer to understand 
them when he endeavors to make a fight against the diseases 
of domestic animals than it is for the physician or the veterinarian 
who tries to cure the disease. With animals, as with man, the 
individual resisting power is variable. When a lot of pigs are 
attacked by that very fatal disease, hog cholera, some of them 
escape with no signs of the disease, showing a superior resisting 
power. Undoubtedly the resisting power of animals is due to a 
proper physical vigor, little understood, but plainly dependent 
upon proper conditions of life. Let the conditions be normal, 
and the animal may resist the attack of parasitic bacteria; but let 
them become abnormal, so as to reduce vitality, and the animal 
is much more likely to succumb. 
Tuberculosis, for example, is much more prevalent among 
cattle that are kept stabled most of the time, than among those that 
spend a considerable portion of the time in the open air. This may 
be due, in part, to the fact that stabled cattle have a greater chance 
of acquiring the contagion, since they are kept so close together. 
But this is certainly not the whole reason. Young cattle that are 
kept in the open for a year or two are less liable to take the disease 
