demonstrate their natural and logical interdependence and their relation to the end or purpose for which their investigation is made. It is the power of doing this that distinguishes the handicraftsman in medicine, and in every art, from the true artist, and enables its possessor to demonstrate what is proper and essential to the subject or thing investigated, and raises him above the mere clerk who records, or the photographer who imitates, and assimilates him to the author who inspires and the artist who creates. This faculty, which has been called the scientific imagination, is not the faculty of the poet, by which he sees things that do not really exist, but the power of mentally conceiving or realizing the whole of a picture of which a part only is presented to the senses. It is this scientific imagination which derives its value from the uniformity of nature, and enables one not to speculate at random under the spur of the imagination, but by obeying the laws of cause and effect, and the associations which nature infallibly creates, to become a faithful intepreter of nature's laws. It is this faculty which essentially distinguishes the philosopher from the poet, and enables one to follow a straight path on the firm earth, while the poet on the wings of his imagination soars beyond the verge of human reason.
I venture once more to repeat my lifelong declaration of faith that every art must exist before its associated science, and that, how much soever each may illustrate the other, both are essentially independent. Neither botany, nor chemistry, nor pharmacy, nor pharmaco-dynamics, nor physiology, nor bacteriology, is an essential part of therapeutics. Its true and only foundation is clinical medicine, the medicine which recognizes and treats diseases. Medicine, in this sense, is an art and not a science; its laws are rules established, not by theory, but by observation and experience. They are as various as the medicines employed or as the patients who take them; they must be modified by the nature, the form, the tendencies of the particular disease, by the external and the internal conditions and relations of the patients. The certainty of a science depends upon the fixity or constancy of its elements; the uncertainty of the healing art is due to the inconstancy, the fluctuating values of the elements involved in the disease, in the remedies, in the patient, and in the physician himself, elements which no science has ever measured or reduced to law, and which none probably ever will; but what science has failed to do for disease in general, and for classes of diseases, practical sagacity has accomplished for indvidual patients.
