RESISTANCE AGAINST MICROORGANISMS. 255 



personal vigor will do rnore toward 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 



