Experimental Study of Health and Disease
Until the middle of the last century very little had been done in the way of experimental study of physiology and pathology. Physicians depended almost entirely on bedside observations. Some of these physicians were wonderful men, and often their observations were remarkably shrewd. But the human body is a complex machine, the organs are so interdependent, that in the presence of any given set of symptoms and signs of disease, it was almost impossible to be sure just what caused them, and, consequently, what was best to do for the patient. When the experimental method was adopted disease could be observed systematically, conditions could be controlled, and the phenomena that resulted could be studied intelligently because the experimenter knew exactly what had produced them. In such experiments mammals are the animals chiefly used, because in most respects they most nearly resemble man, himself a mammal. Practically all the domestic mammals have been used, horses, cattle, sheep, goats, swine, dogs, cats, rabbits, guinea-pigs, and rats and mice; monkeys are also used. And all have made wonderful contributions to medicine or surgery or both.