A knowledge of the causes of disease is highly important as a means of prevention. When causes are traced to their origin, their influences can often be obviated. It not unfrequently happens that ignorance of etiology largely prejudices recovery, when a knowledge of the morbid influences, still operative, might be removed.

The term traumatic is used to distinguish certain causes. Anything which occasions an injury or wound of a part, from which disease results, is a traumatic cause. Certain diseases, the origins of which we are unable to appreciate, are termed spontaneous.

Predisposing or exciting causes are influences that induce a tendency or liability to certain affections. They alone may be sufficient to give rise to disease, or they may only suffice to so influence the system, the conditions will be favorable for the occurrence of it.