These may be stated together, thus : as causes which are

Hereditary : examples (though not always inherited), consumption, gout, epilepsy, cancer.

Functional: that is, depending upon the action, either too great or too little, of one or more of the organs, or of the body generally. Examples: over-exertion, over-excitement, loss of sleep ; or, on the other hand, want of exercise.

Mechanical: as wounds or injuries of various kinds, tight-lacing, etc.

Conditional: as extremes of heat or cold, sudden changes of temperature, dampness of dwellings.

Digestive: as poisoning, unwholesome food, intemperance, abuse of medicine; and, on the other hand, starvation.

Obstructive: as neglect of the bowels, uncleanliness of the skin, ill ventilation.

Contagious: as small-pox, itch, hydrophobia.

Atmospheric: as autumnal fevers, yellow fever, cholera.