The experimental method in the conquest of disease / by Sir Edward Mellanby.

  • Mellanby, Edward, Sir, 1884-1955.
Date:
[1939?]
Catalogue details

Licence: In copyright

Credit: The experimental method in the conquest of disease / by Sir Edward Mellanby. Source: Wellcome Collection.

    6/18 (page 4)
    You notice that this problem of probably a million years’ standing was settled by the experimental method immediately it was used for this purpose. This instance—one of thousands—forms a striking example of the relative power of the experimental and observational methods to supply information about the body. If all the clinical conditions encountered by the physician were as simple as Bell’s palsy, the need for animal experi¬ ments would be greatly reduced although, even in such cases, animal experimentation would be necessary to determine the function of the nerves and other organs at fault. Usually the physician only recognises what he is looking at because of the knowledge brought to him by the experimenter who, by simplifying his experimentally produced conditions and analysing their effect, has been able to teach the clinician the functions of each structure and what happens when this structure is absent or abnormal. The acquisition of knowledge by making comparisons is common both to the experimental and observational methods, and it is this factor which again often introduces confusion as to what constitutes an experiment. In the case of an experiment a condition of affairs is noted, and the object of the experimenter is to determine any change that takes place as a result of altering one or more of the conditions. In observational enquiry an individual notes any differences there may be under natural but uncon¬ trolled circumstances. It is of interest, for instance, to find that Claude Bernard regarded the recording of the pressure at the base of a tower and comparing it with the pressure at the top of a tower as an experiment. In this case, however, although there is comparison, there is no question of actively altering the environment. Nowadays it would probably be said that such an operation would be regarded only as a comparison of two observations and not in the nature of an experiment. Similarly, a clinician may find that the blood pressure in the artery of the foot is higher than the blood pressure in an artery in the arm, but the mere recording of this difference does not involve experiment but only two observations. If, however, the clinician compares the differences in pressure between the hand and foot when the patient is sitting down and when standing on his head, he is doing an experiment, because he is altering the environmental conditions and determining the effect of this alteration on the differences in blood pressure. In other words, by actively interfering and choosing his conditions he is being taught by nature the effect of alteration in posture on a certain physiological phenomenon. When he observes differences in pressure between the radial artery and the foot artery, he is only observing and comparing and, although he may think that this difference is due to posture, he cannot know this until he has done the actual experiment. One of the fundamental properties of the experimental method is that a particular experiment always records the absolute truth. The words <c good ” and “ bad ” in connection with an experiment have no meaning at all, except in so far as they reflect the goodness and the badness of the experimenter. The actual effect of the alteration of conditions during any experiment is determined and certain, whatever may be the ability of the