Preventive Medicine includes the application of everything that physiology, hygiene, sanitary science, etc., can teach to lessen the development of disease according to the teaching in § 4 of the Organon.

"The physician is at the same time a preserver of health, when he knows the causes that disturb health, that produce and maintain disease, and when he knows how to remove them from healthy persons".

It includes much of bacteriological knowledge, antiseptic medication, subjects that have made enormous strides in recent years. It includes as well the judicious use of homoeopathic remedies in preventing or modifying the development of epidemic and hereditary diseases.