The effect of solvents on the absorption spectrum of a simple dye: WALLACE R. BRODE. The absorption spectrum of benzeneazophenol dissolved in thirty organic solvents and in mixtures of some of them was measured in the visible and ultra-violet. No definite relation was found between the frequency of the absorption bands and either the refractive indices or the dielectric constants of the solvents, except for solvents of the same homologous series. When dissolved in a mixture of two solvents, the absorption band is that given by the dye dissolved in the most polar solvent even if only 1 per cent. of this solvent is present in the mixture. The absorption limits of the solvents for a layer 1 cm thick were measured and form a gradual series of radiation filters between a frequency of 850 and 1,350.

The cathodic deposition of metals: K. FRÖLICH and GEO. L. CLARK. I. Theory of the mechanism: 1. There is no evidence of an intermediate state in the electrodeposition of metals. The discharge of a metallic cation and the subsequent crystallization of the atom thus liberated are two phenomena so intimately connected that they must be considered one process. (2) In the deposition of the metals of the iron group a resistance has to be overcome which can not be traced back to specific properties of the electrolyte. A closer examination shows that the same type of resistance is encountered in the deposition of most metals and gives rise to what is termed the "true metal overvoltage." (3) The true metal overvoltage is highest for metals giving low hydrogen overvoltage and vice versa. By discussing this phenomenon in view of the hydride theory of hydrogen overvoltage, the conclusion is arrived at that the true metal overvoltage is caused by the interference of hydrogen with the process of building up the normal space lattice of the metal, while the discharge reaction itself is a reversible reaction for all metals. (4) The relation between metal overvoltage and hydrogen overvoltage appears to be very helpful in explaining the cathodic crystal formation of the individual metals.

II. A preliminary experimental X-ray study of electrodeposited nickel: (1) Thirty Laue, monochromatic pinhole and powder diffraction photographs have been taken of nickel films electrodeposited on platinum and on aluminum, the films being split off in the latter case. These specimens were deposited from chloride, sulfate, sulfate containing gelatine, complex oxalate and complex ammonium electrolytes. With the sulfate electrolyte the anode metal, temperature, concentration and current density were varied. (2) The structure of the platinum foil is derived from the well-defined figures characteristic of a strongly rolled metal. (3) The metal deposits of nickel all show the tendency of the crystals to orient themselves with the 100 planes parallel to the electrode surface, though under a condition of strain. Powder diffraction spectra characteristic of random orientation were obtained only with the high

Com

temperature electrolyte. With current densities as low as 0.10 amps./cm2 the orientation is maintained. plex ammonia electrolytes give best orientation which must be connected with the vigorous hydrogen evolution and hydride formation. Other deposits are compared. A deposit from sulfate electrolyte split from an aluminum electrode produced a single broad diffraction ring with Mo K alpha rays, thus indicating the extremely small size of the crystals. (4) Copper deposited on platinum at high current densities shows orientation of crystals contrary to other work. (5) The experimental results are interpreted to support in general the theory of the mechanism of electrodeposition presented in the first paper of this series.

On the photochemistry of fluorescent dyes: PHILIP SUBKOW. It is shown that the action of light on the solutions of the alkali salts of eosin and fluorescein causes a photochemical reaction to accompany the fluorescence such that the alkali salt is hydrolized and a colloidal solution of the acid dye is formed. Accompanying this reaction is a photochemical precipitation of the colloid. Ozone or certain oxides in the presence of light apparently aid this reaction. That this reaction does not seem to obey the Einstein photochemical law or the Bunsen-Roscoe law in Wood's experiments is explained by the absorptive effect of the colloidal dye on the incident radiation and effects of convective currents. Further, the so-called protective action is explained as due to the absorption of light by the colloid formed by the temperature hydrolysis of the salt.

The versatility of ferrous hydroxide: PETER FIREMAN. Freshly precipitated ferrous hydroxide, in undergoing oxidation through the action of the air, gives rise to the formation of a long series of well-defined colored pigments, in dependence on slight changes in the composition and conditions of the mother liquor. Black ferro-ferric oxide, yellows of the composition Fe,O,. HO and browns of the composition Fe,0, are briefly described and the broad conclusion is drawn that the oxidation at low temperatures leads to the formation of hydrated oxides of iron yellow in color while the oxidation at higher temperatures leads to the formation of anhydrous oxides of iron.

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The catalytic synthesis of water vapor in presence of metallic nickel: ARTHUR F. BENTON and PAUL H. EMMETT. A study of the catalytic combination of hydrogen and oxygen over metallic nickel has shown that the water formation is accompanied by superficial oxidation of the catalyst. When the surface has become completely covered with oxide the rate of catalysis suddenly decreases to a small value. The reduction of such

a completely oxidized surface by pure hydrogen exhibits autocatalysis, but even the maximum reduction rates so obtained are small in comparison with the rates of hydro-oxygen combination at the same temperature. The evidence indicates, however, that the interface area, on which the rate of reduction depends, is much greater in the catalytic process than in the reduction. The conclusion is reached that the catalysis can be largely and perhaps entirely accounted for on the theory of successive oxidation and reduction of the catalyst.

The preparation of phosgene-salts: ALBERT F. O. GERMANN and CHARLES RUSSELL TIMPANY. In pursuit of the study of phosgene solutions, the ordinary methods of preparing salts were found to be inadequate in the preparation of phosgene-salts. To carry out these preparations, an apparatus has been devised in which 100 grams of crude salt may be prepared and purified by recrystallization and washing in phosgene solution without contact with the atmosphere, by a reaction in which metallic chlorides are neutralized by a phosgeno-acid, as follows: CoAlCl + CaCl2 = CaAlCl + CoCl2. A method of analysis of the product, which carries phosgene of crystallization, is given. The vapor tension and solubility of the salt in phosgene at 25° are given.

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A general theory of solvent systems: ALBERT F. O. GERMANN. Based on the well-known behavior of water and of ammonia solutions, it would seem plausible to expect the typical ions of acids to deviate from the familiar H+ type, just as the typical ion of bases is known to deviate from the OH- type, when a wide variety of solvents is investigated. The term "parent solvent" is defined, and its relation to a system of related acids, bases and salts outlined. Application of these ideas is made to phosgene, which is shown to yield an acid in which CO++ replaces H- of the familiar acids. Reactions of this acid in phosgene solution parallel the reactions of familiar acids in water solution. Applications to other solvents are suggested.

Note on some properties of some soluble borates: F. P. DUNNINGTON. When lithium carbonate in excess is boiled with boracic acid solution, there is formed lithium di-meta-borate. This is very soluble in cold water and may be concentrated to a syrupy consistency, while the corresponding sodium salt, borax, is little soluble. Potassium di-meta-borate, made by mixture of molecular weights of potassium hydrate and boracic acid, is soluble in about four parts of water. Solutions of lithium, sodium and potassium di-meta-borate are alkaline to litmus and to phenol phthalein. If each of these in solution is titrated with boracic acid until neutral to phenol phthalein, it will in each case require exactly one more molecule of boracic acid and so form the tetra-meta-borate. The sodium tetra-meta-borate is soluble in about four parts of water. The stronger water solutions of borates present the antiseptic properties of boracic acid in a more concentrated form than has heretofore been employed in surgery.

Emulsification: BRIAN MEAD. Some unusual results have been obtained, using sodium oleate and sodium stearate as emulsifying agents. Sodium oleate can, under certain conditions, be made to give water in oil emulsions by exposure of its solution to air. Sodium stearate, under certain conditions, will dissolve in oil and will then act as an emulsifying agent for water in oil. The significance of these results is discussed.

The oxidation of benzaldehyde: BRIAN MEAD and J. D. COCHRANE, JR. Benzaldehyde, which is usually considered to be an example of an autoxidizable substance, has been found not to be so. The amount of oxidation which takes place (as measured by the actual absorption of oxygen) is found to depend entirely on the intensity of the light to which the benzaldehyde is subjected. If the source of light be cut off, when the oxidation is proceeding, the reaction ceases after a very short interval. It will proceed at the same rate if the benzaldehyde is again illuminated. Preliminary results with X-rays shows that these do not cause the reaction to proceed at all.

The partial molal heat content of ammonia solutions: GERHARD DIETRICHSON, R. T. LESLIE and J. E. WHITTENBERG. The partial molal heat content of ammonia solutions has been determined at 25° C. over a range of concentrations from 0.1 to 0.7 mol-fraction of ammonia. This was done by means of an adiabatic calorimeter involving a distillation process. The amount of electrical energy required to vaporize definite quantities of water and ammonia from solutions of different concentrations was first determined. The heats of vaporization so obtained were plotted against the corresponding mol-fractions. The partial molal heat contents were in turn obtained by making use of the method of intercepts. The experiments carried out on ammonia solutions represent an attempt to supply some of the thermal data that are needed in connection with the absorption refrigeration process.

The mechanism of the fixation of nitrogen as sodium cyanide: E. W. GUERNSEY and M. E. SHERMAN. It has been found that the formation of sodium cyanide in a heated mixture of sodium carbonate, carbon and iron proceeds by the following steps: Sodium carbonate is reduced to give metallic sodium, metallic sodium reacts with carbon to form sodium carbide and sodium carbide absorbs nitrogen to form sodium cyanide, this latter reaction occurring in the gas phase. Each of these steps has been carried out, and it has been shown to be improbable that there is an appreciable amount of cyanide formed except through this series of reactions. Both the formation of sodium carbide from the elements and the absorption of nitrogen by the carbide are distinctly reversible reactions. Iron appears to exert marked catalytic action only on the final reaction, the formation of cyanide from carbide and nitrogen.

ARTHUR E. HILL Chairman

Three Letters bearing upon the Controversy over
Evolution: PROFESSOR W. C. CURTIS
Scientific Events:

The Museum of Scientific Instruments at Oxford University; The National Museum of Engineering and Industry; Fisheries Conservation Conference; The Lake Placid Meeting of the Metric Associa tion; Field Work of the Victoria Memorial Museum; The Distinguished Service Professorship at the University of Chicago......... Scientific Notes and News University and Educational Notes Discussion and Correspondence:

The Excessive Politeness of American Botanists: DR. D. H. ROSE and DR. NEIL E. STEVENS. On the Daylight Visibility of Stars from a Mine Shaft: CHARLES CLAYTON WYLIE. Twinning in a Mollusc: DR. RICHARD P. HALL

Scientific Books:

Baumgartner's Laboratory Manual of the Foetal Pig: PROFESSOR H. H. LANE

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A CONSIDERATION OF THE CLINICAL AND DIDACTIC METHODS OF

TEACHING MEDICINE

BEFORE undertaking to expatiate upon the main thesis of this essay, it might be well to explain briefly what is meant by the term "the teaching of medicine." Broadly speaking, what is understood by this term is the application of the science of biology, anatomy, physics and physiology, chemistry and biochemistry, pathology and bacteriology, to the study of disease as presented by the patient. It is the correlation of the sciences related to medicine, to the art of achieving a diagnosis of the morbid process from which the patient suffers and to the art of relieving the patient after the presenting symptoms and signs have been interpreted properly. Medicine as distinguished nowadays is further delineated by the adjective "internal," implying that the disease to be recognized and treated lies within the three larger cavities of the body, the cranium, thorax and abdomen, in contradistinction to some of the smaller offshoots from the main stem of medicine which are recognized as the specialties and which deal with lesions of the skin, the nerves or the special senses.

Having defined what is the usual conception of medicine in its broad sense, it should now be possible to trace the development that has taken place in the methods of teaching students in the undergraduate medical schools within the past few years. In the United States, a hundred years ago, the teaching was almost entirely individualistic. A student attached himself to a preceptor, who in theory at least was qualified to guide the neophyte through the intricacies of a medical training. On the one hand, such a method of training had the advantage of permitting the student to come into intimate contact with disease from the start of his training; on the other hand, the great bulk of the preceptors were little qualified to teach and to instruct. In the beginning of the past century such a method of training gradually was succeeded and replaced by the springing into being of more or less inadequate medical schools whose training of the student was almost entirely dogmatic and didactic and who depended for their very existence upon the fees that were collected from the students. Towards the end of the nineteenth century at Harvard, Johns Hopkins and the University of Pennsylvania, as Garrison relates, "medical teaching began to be true university teaching, in the sense of

training a student to make use of his own mind as a substitute for blind acceptance of dogma." Despite these beginnings, we find that at the beginning of the present century there were hosts of medical schools of low standards, with insufficient clinical facilities, teaching almost entirely didactically large numbers of medical students. So great had been the increase in medical schools and students that we find in 1904, when the American Medical Association began its campaign to elevate the standards of medical education in the United States, that there were in existence 162 medical schools with an enrollment of 28,142 students. As a result of improved standards of medical education, the number of schools teaching medicine and fulfilling the requirements satisfactorily has fallen to 55, with a student enrollment approximately one third smaller than in the peak year, 1904. The quantitative fall in number of students has been accomplished by qualitative betterment in the type of the student body and a corresponding improvement in the medical graduate. The explanation of the better grade of practitioners now being turned out by the medical schools is that, with the decrease in number of students, greater opportunity has been afforded those in the school to study at first hand disease as it was presented by the patient. The advantages of this type of teaching, the so-called clinical teaching, are so obvious that they hardly need to be reiterated, but for the purpose of review they will be briefly enumerated.

In the first place, such a method of teaching permits the student to see and to follow up the usual run of cases as occur in the in- and out-patient department of a hospital. He is thrown into intimate contact with such types of cases as he will meet in his postgraduate work and in his practice. He learns the life cycle of disease at first hand and he learns how to diagnose and treat the disease from personal observation of the patient. The unusual, abstruse and difficult cases are not picked out for him to study and are not accentuated as they were in the old days when the teacher would select such cases for the purpose of delivering a brilliant lecture. On the contrary, he sees patients as they come into a service and only occasionally meets a case of some exotic disease. Secondly, the protagonists of clinical teaching maintain that the time spent in lectures is time wasted. Much better would it be were the student to employ the lecture hour in reading or in the objective study of a patient than, parrot-like, to copy the words of one who has prepared his lecture largely from a text-book. On the other hand, in a clinical talk with the patient before him, in contradistinction to the formal lecture, the teacher is enabled from a

concrete example to enter into a full discussion of the disease as presented by that patient, as seen by him in other patients and as studied in various phases and in minute detail by investigators throughout the world.

Another advantage of clinical teaching lies in the fact that it is more thorough. It is an inherent characteristic of the great body of mankind that they are better able to remember what they have seen than what they have heard. And this faculty of remembering is greatly enhanced because the student is given the opportunity of not briefly seeing the case, passing in review as it were, but of actually spending hours and even days studying the various manifestations of the disease.

Lastly, and probably more important than all the other advantages of clinical teaching, is the training it gives the student in the use of his eyes and his ears and his sense of touch. He learns to use his senses, to make proper deductions from what he has observed and then he learns to cultivate his mind; he learns the art of reasoning and he trains himself, he becomes experienced-factors which are of prime importance in learning any science.

All these statements are well recognized. The increase in the length of the curriculum that has come about in the past thirty years is merely recognition of the fact that a student must dissect, must use his microscope, must titrate his specimens and must work on the patient. The increased hours the student spends in his learning of medicine are not devoted to new subjects as much as they are given over to the individual doing and seeing, deducting and reasoning, rather than merely hearing and copying.

But the question comes up: Are we not allowing the student to spend too much time in practice and are not his efforts, particularly in internal medicine, likely to be too unsystematic? Didactic teaching has many advantages, in spite of the fact that the pendulum has swung far away from it and that in many universities in the teaching of medicine it has been done away with almost entirely. Among the advantages that it presents, when used in moderation, is that it affords opportunity for the arrangement of a systematic course in medicine. One disease after another can be taken up in a definite and fixed order and the clinical teaching can be so correlated with the didactic that greater interest is aroused in the student when he sees what he has been recently told than when he is thrown precipitately into the study of a new case. The reading of the student can also be better correlated than when he is presumed to be following a course of reading and studying without definite guidance. This is supposedly obviated

by conducting classes and quizzes in some systematic manner, but such a method of teaching is only a variation and not a difference in didacticism. Unless there is some such definite guide, practically a student does not follow any comprehensive plan in his studying.

From the pedagogic standpoint, we may assume that the clinical or practical method of teaching is the ideal, but from the point of view of a practical educator there is always before the student various examinations which he will have to take after he has left the medical school and before he becomes a qualified physician. It is all right to say that, if a student learns to study one type of case thoroughly and properly, when he sees an unusual type of case which he has never seen in his student days (and no hospital can show in two years every type of disease and disorder), he will be able to study this new case in a suitable and proper manner. But hospital examining boards and state boards do not know this nor do they know what diseases a student has seen or has not seen. Therefore it behooves the student, if he is to pass examining boards not connected with his university, to learn more or less about every disease and it behooves the instructor so to teach the student. Much as the necessity of this is to be regretted, it is not a theory and must be faced. A medical school must not only train the mind and the intellect of its students, but it must also give them such instruction as will permit of their being allowed by state authorities to exercise their presumably well-trained abilities.

Lastly, one of the very real advantages of a course of didactic lectures lies in the inherent value of the first-hand opinions and ideas which the head of a department is enabled to give his teachers and his students. In no other way is the man who is presumed to be best acquainted with the theory and practice of medicine able to get together as one group all those associated with him and to tell them what he feels and thinks and knows about disease and so to correlate the teaching in his department that it may be a cohesive whole. The leader should lead. This he can not do, at least in purely physical teaching, even if we presume that he has great abilities as an executive, as a stimulator of research or as a leader of men, if his energies are devoted only to such small groups of men that many in the class never have the opportunity of seeing his methods or attaining his point of view.

The objections to and disadvantages attributed to didacticism are numerous, but the chief criticism of those who believe in the clinical methods of teaching is that it abolishes or at least minimizes the advan

tages inherent in this, the clinical, method of instruction. By this rather paradoxical statement I mean to imply that education, without training of the student's mind to deduce facts from observations, without allowing for the development of his initiative and without giving him opportunity of developing his reasoning power, is in no sense real education and that without these attributes a man may mimic a medical education but he is not an educated, trained physician. Minor points of attack in the didactic method of teaching include waste of time to the head of a department and to the student. In the case of the first individual it is said that the preparation and delivery of a lecture is time-consuming without compensatory advantages. The hour that is spent in delivering a lecture is preceded by many long hours of preparation, for a good lecture is not a spontaneous outburst of oratory, but a prepared, systematic marshalling of facts, from personal knowledge, from text-books and from current medical literature in an orderly fashion so that the whole subject is discussed in toto thoroughly. For the second individual, the student, the waste of his time lies in the knowledge that the greater part of what is said in the lecture can be read in a text-book, and read repeatedly in a time equivalent to that devoted to listening to a lecture.

To those who hold that a certain number of didactic lectures are necessary in teaching internal medicine, certain basic faults of clinical teaching present themselves. The lack of system is the first. It has been discussed sufficiently. Another difficulty is that a large amount of clinical material is necessary to give the student opportunity of studying many cases and such material is not always available without very extensive hospital facilities. More teachers are required, because a group of students can not be turned loose in a ward or clinic without the guidance of some one properly qualified to aid them. The need of much material and a large number of instructors is a very real difficulty to those schools which are not heavily endowed and whose budgetary troubles are ever-present. Lastly, it frequently happens that to one student there may be assigned in his two years of practical work a series of patients who present almost identical diseases. One man may have the misfortune to see only heart cases; another, patients with metabolic disturbances only, while a third may have the ill luck to work with a group of unusual cases which he will rarely if ever see in his subsequent career. Nor can this difficulty be avoided. Because of the need of a large number of patients it is impossible for one man to assign to the students each case and to keep track of those diseases which