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ing. This, too, should explain the common tendency in such patients to keep the limbs moderately elevated when sitting, such elevation being insufficient to occasion much difference in the gravitation of the column of arterial blood but making an important difference in favor of more easy venous return from the limbs (the difference of height of the lower pelvic level and the floor).

These examples of the type of questions to be presented to the student in medical physics are crudely and but incompletely drawn; but they serve the purpose of illustration here desired and indicate the objective aim in urging the adoption of a definitive course in the subject. They are both well suited to actual laboratory demonstration, but not more than a host of other possible instances. In fact, in the arrangement of a course it must be a matter of selection from the great number of examples possible; and the fullest scheme could not possibly deal with more than types, leaving the individual applications to the intelligence and resources of the student for determination. It could not do more than attempt to inculcate a habit of thought along these lines, aroused by witnessing typical illustrations; and in the end this is one of the real purposes of every education-the establishment of a method of observation and of mental reflection and application of principles to the clinical problem of the physician. Beyond this, the crowded condition of the curriculum would give but little justification for fuller work.

This matter of urging the adoption of a definite system of instruction in medical physics applies particularly to our American medical schools. For a decade or more in Great Britain it has come to be a required study for those applying for the ordinary qualifications; but in the university courses in medicine and surgery it was demanded for a much longer time. Much the same may be said of the continental universities as for those of the British. In our own country a demand for a certain amount of knowledge of elementary physics as an entrance requirement is common to all the schools holding membership in the American Medical College Association as well as to a number outside this organization. For the most part this requirement is worth nothing, or very little bet

ter; in some instances the branch is but an elective in these requirements. In comparatively few college catalogues is the amount fixed at any really important grade. Inspection of catalogues show, too, that in but a very small minority of our schools is there provided any additional work in the medical aspects of the subject; and of these few it is not at all sure in some but that the physics taught is absolutely elementary and rather introductory to chemistry, with which it is usually associated, than an applied medical physics. There are a very small number of American schools in which the catalogues indicate a really commensurate and suitable presentation of the branch, and this number by no means includes all of the schools of the highest reputation in the land. Nor does there occur to the writer, in examining the prospectuses of the year or from personal knowledge or information obtainable, that there is any real tendency to remedy what after serious thought he has come to look upon as an unjustifiable negligence.

I confess to a twofold object in this sketchy presentation of what I fear is not a popular subject. The first is of course that of attracting the interest of the members of the Association to the importance of medical physics in itself and to its rather common disregard in most of the American schools of our profession; but I have more directly in mind the intimate relations of this Association to the State and its medical school. In the Medical Department of the University of Texas no preliminary knowledge of physics is asked the student about to matriculate. From early in its

history the professor of chemistry, Dr. S. M. Morris, has devoted in the first half of the Freshman year two hours weekly to a lecture and demonstrative course in the subject with special reference to its bearings in medical study, but has been unable, principally from lack of space and appropriate equipment to develop the actual and needed laboratory course above suggested. It is unlikely that it will be possible for years to come to demand such degree of preliminary knowledge of the subject that it might be dropped from the course, were this desirable; since entrance demands from professional schools must in distinct degree depend on as well as lead

popular education. It is toward the establishment of a fuller, more practical and more directly medical course in physics in our home school that in closing I wish to leave your thoughts, in which wish I know the ideas of my colleagues in the faculty of the school and my own are in accord; and for which I am in position to know that the Regents of the University, advocates of progress wherever and whenever possible, are powerless, as in many other features of the school where advances and expansions are desirable, solely because of financial disability. I would not ask of you any concerted action in any of these matters, since such action is apt to be transient in its influence and of less value than individual effort; but I would ask of those of you to whom this paper may have appealed as reasonable to use your personal powers and influences to create in our State a popular interest in and willingness for the school to advance, not only in the limited lines indicated in this paper, but in all lines leading to the highest attainable efficiency.

THE FERMENTATION THEORY OF INFECTION AND

IMMUNITY.

J. W. MCLAUGHLIN, M. D.,

PROFESSOR OF MEDICINE, SCHOOL OF MEDICINE, UNIVERSITY OF TEXAS.

"He that thoroughly understands the nature of ferments and fermentation shall probably be better able than he that ignores them, to give a fair account of divers phenomena of several diseases (as well fevers as others), which will perhaps be never properly understood without an insight into the doctrines of fermentation."-ROBERT BOYLE (essay on the "Pathological Part of Physik").

In 1828, when Wöhler synthetized urea, modern physiological chemistry was born; and at the same time it was demonstrated beyond a peradventure that the peculiarities of organic substances are the result solely of the properties of carbon, their chief constituent. From that day until this, it has been more and more clearly demonstrated that the so-called vital processes are but highly specialized chemical and physical phenomena, such as are daily encountered in our laboratories. The recent work of Loeb, which carries into the realm of physiology the work of Van Hoff, Arrhenius and others, is a gigantic stride in the demonstration initiated by Wöhler. It is attempted in this paper to follow in the footsteps of the masters in so far as the principles of molecular physics are utilized to explain certain quasi-vital phenomena.

NOTE. The principles of molecular physics, involved in the explanation of fermentation by the author, were utilized by him as far back as the 80's to explain the mysterious action of medicine on the living organism; and in 1890, in an abstract of a paper on fermentation, immunity, and infection, read at an annual meeting of the American Medical Association, these same principles were held to underlie the phenomena of these processes. In 1892, this subject was more fully elaborated in a small volume, which was published by the author, entitled "Fermentation, Infection and Immunity."

That the phenomena of fermentation and of infection and immunity are strictly analogous processes, and that these analogies point unerringly to a common causation, has been recognized for more than three hundred years; yet the common cause has heretofore remained a mystery. It is the purpose of this essay to present an explanation of those phenomena based upon accepted theories of molecular structure and molecular energy.

Fermentation, broadly speaking, is a chemical or chemico-physical change induced in certain substances by specific bodies, themselves unchanged, and resulting in specific products. These changeinducing bodies may be divided into (a) living ferments, and (b) non-living enzymes. In a narrower sense the term "fermentation" is applied merely to changes induced by living ferments; while the term zymolysis or zymosis is reserved for that produced by enzymes. Living ferments are micro-organisms which are widely distributed in nature, including many bacteria, blastomycytes and some moulds. Enzymes, or non-living ferments are bodies which are formed within living cells of animals or plants of the higher order of life. The two classes of ferments present many points of similarity in their action; for example, both classes work best at practically the same temperature, about that of the normal human body; both are destroyed by boiling, either will cause insoluble substances to be transformed so that they pass into solution; each is hindered, and may be arrested, in its action by the products of its own activity; neither adds anything from its own substance to the ferment products; and each manifests selectivity, in that a definite structural relation must exist between the ferment and the fermentable substances in order that fermentation or zymolysis may take place. "We know that the properties which are supposedly characteristic of the enzymes are possessed also by certain elements which are found only in the inorganic world. The most notable property of the enzymes is their ability to effect an amount of change which is out of all proportion to the quantity of the enzyme present, and the fact that the enzyme itself apparently does not enter into the reaction. These properties, however, are com

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