Instead of microbes being the cause of disease, they are at most only capable of joining with the culture media to develop an affection--certainly not a disease. As cause, bacteria must be classed with the elements and other influences in man's environment which are good or bad for him, depending on his health--resistance.

Efficient cause is anything powerful enough to produce primary disease. There are chemical causes--poisoning--and animal toxins. The poison that can prostrate and kill man must be able to overcome his normal resistance. Nothing belonging to man's normal habitat can break down his normal resistance; hence the idea that germs unaided cause disease is a delusion which the medical world must outgrow, as likewise the idea that serum can antidote germ influence; for germs have no influence except as they join other auxiliary influences and break down resistance.