a product was isolated from the urine which has been identified as the phenyluramino derivative of cysteine.

Avian versus mammalian dietary requirements: W. D. RICHARDSON.

The influence of fasting and of vitamine B deprivation on the non-protein nitrogen of rat's blood: H. A. MATTILL. The non-protein nitrogen of the blood of fasting rats is 30-40 per cent. higher than that of normal animals, the most marked increase being in urea. Creatinine and creatine are very slightly increased as are total solids. The blood of rats deprived of vitamine B shows practically no variation from the normal except that creatinine is at the fasting level and creatine is slightly higher than the fasting figure. In the present state of uncertainty with reference to the determination of blood creatine and creatinine these variations are of little significance but at least the total solids, the non-protein nitrogen and the urea fraction in the blood of rats on a diet deprived of vitamine B are normal and not increased as in the blood of fasting rats. The desirability of obtaining information on the gaseous metabolism as well as on creatine metabolism in animals deprived of vitamine B is suggested.

The effect of temperature and the concentration of hydrogen ions upon the rate of destruction of the antiscorbutic vitamin: H. C. SHERMAN, V. K. LAMER and H. L. CAMPBELL. The time curve of the destruction in filtered canned tomato juice follows neither the unimolecular nor the square root law of Schütz when the heat treatment is conducted at 60°, 80°, 100° C. for 1 to 4 hours. Empirically the destruction in these cases was found to be a function of the fourth root of the time. The temperature coefficient of the destruction of the vitamin was low: Q10 (60°-80°) =1.23; Q10 (80°-100°)=1.12. The low temperature coefficient and the colloidal nature of the material indicate that in tomato juice, at least, the reaction is of the heterogeneous type with diffusion playing an important rôle. Oxidation by oxygen can not be an important factor in these experiments. The velocity of the reaction at 1 hour at 100° C. progressively increases with decreased (H+). The omission of reacidification following such treatment produces an even greater destruction due no doubt to the continued action of the greater (OH-) even at low temperature. The quantitative measurement of the antiscorbutic vitamin: H. C. SHERMAN, V. K. LAMER and

H. L. CAMPBELL. Guinea pigs are fed a basal diet consisting of oats 59 per cent.; skim milk powder heated 2 hours at 110° C., 30 per cent.; butter fat, 10 per cent.; NaCl, 1 per cent. In addition to the determination of the minimum protective dose of antiscorbutic the degrees of scurvy produced, as measured by the autopsy findings, retardation in growth, and symptoms in life, are determined for a series of animals receiving graduated sub-protective doses of antiscorbutic food. When the dosage is calculated per unit of body weight it is possible to distinguish the degrees of scurvy produced for addenda of antiscorbutics differing by 15 per cent. or less. The per cent, destruction due to a deleterious process is obtained by comparison of the degree of scurvy produced in a series of standard animals fed a similarly graduated series of doses of the treated product. The probable error of the mean in a series of 5 or more animals is less than 4 per cent.

The action of nitrous acid on casein: Max S. DUNN and H. B. LEWIS. Deaminized casein has been prepared by the action of nitrous acid on casein. Analysis by the Van Slyke method for free amino nitrogen showed the absence of free amino nitrogen. Casein and deaminized casein were hydrolyzed and analyzed by Van Slyke's procedure for the determination of characteristic groups. In harmony with the current theories as to the nature of the free amino groups of the protein molecule, lysine was found to be absent in deaminized casein. No other notable differences were detected between casein and deaminized casein. Tyrosine was determined by the FolinDenis colorimetric method. Deaminized casein was found to contain a lower percentage of tyrosine than casein.

Lipase studies. The hydrolysis of the esters of some dicarboxylic acids by the lipase of the liver: A. A. CHRISTMAN and H. B. LEWIS. On the basis of the acidity developed when the lipase of hog liver was allowed to act on the diethyl esters of succinic and malonic acids, it is considered that the reaction proceeded to an equilibrum which corresponded to the removal of one ethyl group from the diethyl esters. A substance was obtained from the products of the reaction between diethyl malonate and lipase which gave on analysis figures which were in good agreement with those required for monoethyl malonate. Lipase of hog liver was not able to hydrolyze monoethyl malonate or potassium ethyl malonate.

Vitamines in milk: (By title.) H. STEENBOCK, MARIANA T. SELL and E. M. NELSON. The writers have been able to substantiate Osborne and Mendel's findings that at least 15 c.c. of milk are required daily to cover a young rat's requirements for the water soluble vitamine. Generally speaking, milk can not then be considered a good source of either the water soluble vitamine or the antiscorbutic vitamine, as our previous investigations and those of others have already shown. This conclusion is emphasized by the fact that it has now been found that approximately 2 c.c. of milk are necessary to furnish a sufficiency of the fat soluble vitamine, which shows that milk fully equals in value, with one exception, our best known sources of this dietary constituent. This figure can not be taken as absolute, however, for even under practical farm conditions a many fold variation in fat soluble vitamine content easily obtains as the ration of the cow changes. Sudden variations in vitamine content are probably in large part prevented by drainage of the storage reservoirs of the animal. Liver tissue for one has been found to depreciate in fat soluble vitamine content on a fat soluble vitamine poor diet. Yet in the aggregate even this effect can not be very prolonged.

Further experiments on the isolation of the antineuritic vitamine: ATHERTON SEIDELL. In a previous paper (Public Health Reports, April 1, 1921) it was shown by control tests on pigeons that the precipitate obtained by addition of ammoniacal silver nitrate to a purified vitamine extract made from yeast "activated" fuller's earth is highly antineuritic. This vitamine silver complex is amorphous and its conversion to a crystalline condition has not been effected. Attention has, therefore, been directed towards the preparation of crystalline derivatives of the active constituent of the compound. Among those which have been obtained are the picrate, nitrate and what appears to be the free base. Of these, the picrate does not give a constant melting point and yields pieric acid by ether extraction. The nitrate melts with decomposition at 146°.

The base is very slightly soluble in strong alcohol but so soluble in water that a viscous pellicle is usually obtained on slow evaporation of the aqueous solution. The physiological testing of these products has not been completed.

The occurrence in the animal organism of two types of lipases: VICTOR E. LEVINE and FRANCIS J. MCDONOUGH. Lipase was found in all the

organs of the pig that have thus far been examined. By the action of bile or bile salts (sodium glycocholate and sodium taurocholate), the lipolytic enzyme may be differentiated into two types: a-lipase and B-lipase. The former is observed only in the pancreas or in its secretions. Its activity is accelerated by bile or bile salts and by heated blood serum. The latter is found in all the other tissues tested. Its activity is also accelerated by serum, but is markedly inhibited by bile or bile salts. The contrasting effect of bile salts therefore serves to distinguish the exo-lipase of the pancreas from the endo-lipase of all other organs. In the light of these experimental results Cohnheim's contention, that no difference exists between an exo-enzyme and its corresponding endoenzyme, is untenable. In view of the similarity in the action of serum upon a-lipase and upon ßlipase it is probable that the two types possess the same groupings or chemical nuclei in their molecular structure. The dissimilarity in the effect of bile salts may be the result of tautomeric modification, or may indicate a difference in stereoisomeric configuration or a variation in the side chains or substituents in the major groupings of the enzyme molecule.

The distribution of lipolytic activity in the kidney: VICTOR E. LEVINE and SALVER A. GIANELLI. Studies were made of the lipolytic activity of the kidney of the rabbit, dog, sheep, pig and cow. The source of enzyme was a chloroformwater extract of the anatomical regions of the kidney, cortex, upper medulla and lower medulla (papillary portion). Ethyl acetate, ethyl butyrate, methyl salicylate, olive oil and castor oil served as zymolytes or substrates. Quantities of extract equivalent to 80 mgs. of tissue were employed, and the lipolytic activity determined by titration, in the presence of phenolphthalein, with N/25 or N/50 sodium hydroxide. When olive oil or castor oil was used, titrations were made after the addition of alcohol. The two kidneys in the same animal always show a distinct variation in lipolytic activity. The greatest lipolysis is regularly observed in the cortex, the least in the lower portion of the medulla (papillary region). The relative extent of lipolytic activity corresponds to the relative distribution of fat in the kidney as recently reported by Christianna Smith (Amer. Jour. Anat., 1920, 27, 69). This distribution in accordance with the anatomical divisions of the kidney explains the preponderating occurrence of fat in the cortex under normal conditions

and also under those of fatty degeneration. The large number of contradictory findings concerning the presence or absence of enzymes in the kidney and the inability of investigators to find normals for this tissue rest upon the failure on their part to consider the kidney with reference to its anatomical regions.

Uric acid and phenols in the saliva: M. X. SULLIVAN and PAUL R. DAWSON. Salivas collected in 30 minutes under, stimulus of chewing paraffin were freed from protein by treatment with 10 per cent. trichloracetic acid followed by 10 per cent. sodium tungstate in 2/3 N H2SO, and were then tested for uric acid and phenol. The uric acid precipitated by silver lactate in 5 per cent. lactic acid, after appropriate treatment, was estimated colorimetrically. The phenols in the filtrate from silver urate, after appropriate treatment, were estimated colorimetrically with resorcinol as standard. Both uric acid (urates) and phenols (free and conjugated) were found in normal saliva and in the saliva of pellagra patients.

Extraction and estimation of lipoids in cereal products: O. S. RASK and I. K. PHELPS. Ether extracts from cereal products, raw or cooked, do not represent their total lipoid content (fatty matter). A preliminary treatment of such products by an ammoniacal alcohol solution and a subsequent extraction by a mixture of ethyl ether and petroleum ethers in a manner similar to that specified in the Roese-Gotlieb method for fat in milk, yields higher results which appear to represent more nearly the true lipoid content of cereal products. Ether extracts of uncooked cereal products represent on the average 65 to 70 per cent. of the results obtained by the above procedure.

Estimation of phospholipins in cereal products: O. S. RASK and I. K. PHELPS. A further study of the lipoids referred to in the preceding abstract indicates that they contain all phospholipins present in cereal products and the lipoid phosphorus of cereals may be estimated by determining the phosphorus content of their lipoids thus obtained.

Resemblance of the thermal death point of bacteria to chemical reaction: W. D. BIGELOW. The data presented by W. D. Bigelow and J. R. Baty in the Journal of Infectious Diseases for December, 1920, can be expressed in the form of semilog curves which are straight lines between the temperatures of 105° and 125° C. At higher temperatures the experimental evidence is inconclusive because of error produced by the time required for heat to penetrate to the center of the tubes.

For this reason the time secured by extending the semilog curves mentioned above is more nearly correct than the experimental data for temperatures above 125° C. At temperatures below 105° C. the time necessary for the destruction of spores appears to be less than would be indicated by an extension of the semilog curves. The semilog curves showing the thermal death point of spores of the fifteen bacteria referred to are all parallel to each other. It is suggested that if other spores follow the same law the position of the curve showing the time necessary to destroy the spores at various temperatures is fixed by the determination of the time at one temperature. It is suggested that the thermal death point of non-sporebearing bacteria at different temperatures will probably follow the same law or a similar law.

The intensity of light necessary to initiate a photochemical change in the retina: E. L. CHAFFEE and W. T. BOVIE. This investigation concerns the potential differences which are set up in the retina when it is illuminated. An apparatus is described in which the differences in potential are amplified by audions through stages. An Einthoven galvanometer is used. The changes are recorded photographically. A single exposure gives three distinct deflections. It was shown as a new contribution that these deflections are greatly influenced by experimental conditions, such as the length of time which has elapsed since the eye has been excised. Over a range of intensities which are very close to the threshold for human vision the height of the first deflection is proportional to the amplitude of the light vibration. An "antidote" for a "poisoned electrode": W. T. BOVIE.

Abiotic action of rays due to ozone and the heat sensitization of protoplasm by ultra-violet light: W. T. BOVIE. The experiments concern the processes which take place in Paramecium caudatum during the time between the exposure to fluorite rays and the appearance of the first visible effects of the radiation; that is, during the so-called "latent period." The latent period is shorter and the effects of the rays are more intense the higher the temperature to which the organism is raised and the longer the time the organism is maintained at the higher temperature. No similar effects are observed if the organism is subjected to the increased temperature immediately before the radiation instead of after it.

CHARLES L. PARSONS, Secretary

FRIDAY, SEPTEMBER 2, 1921

THE SPIRIT OF INVESTIGATION IN

MEDICINE 1

THE first Greek poet of whose personality we are certain, Arctinus of Lesbos (B.c. 770), sharply differentiated medicine and surgery, and held medicine responsible for the advancement of medical science. He relates how Esculapius "endowed one of his sons with nobler gifts than the other; for while to the one, Machaon, he gave skilled hands to draw out darts, make incisions and heal sores and wounds, he placed in the heart of the other, Podilarius, all cunning to find out things invisible and cure that which healed not." How can we, disciples of Podilarius, best proceed in this day and generation to "find out things invisible and cure that which heals not "?

The problem is as old as medicine itself The story of medical investigation unfolds itself in the history of medicine. Progress comes through ideas. Great investigators have appeared from time to time in medicine. They have contributed new ideas, in the elaboration of which they recorded new observations, recognized new facts, established laws, advanced the art of practise, and thus developed the science of medicine. As time passed the socalled underlying or fundamental sciences evolved, and in turn made fresh opportunities for the medical investigator, but they have taken a large proportion of medical investigators from the field of active practise. Some are still left who are attempting to "find out things invisible" and to solve the ever-present problems of treatment of the sick.

Recently, to further such ends, a national Society for Clinical Investigation was created (1909). According to the constitution the objects of this society are "the cultivation 1 From The Mayo Foundation, Rochester, Minnesota. President's address before The American Society for Clinical Investigation. May 9, 1921.

of clinical research by the methods of the natural sciences, the unification of science and the practise of medicine, the encouragement of scientific investigation by the practitioners, and the diffusion of a scientific spirit among its members." Broadly speaking, these simmer down to the better care of the sick, the broadening of the bounds of medicine, and the development of the physician himself.

To the public generally, medical investigation makes no great appeal. The research worker is commonly regarded as impractical. Yet the routine practise of to-day is based on the investigation of yesterday. Wassermann tests, renal functional tests, and spinal fluid findings constitute substantial phases of the medical practise of to-day. Yet, we did not have them fifteen years ago. The public and many physicians fail to appreciate that practise is based on investigation, and that clinical investigation means better care of the sick, greater public health, and happier communities.

Investigation is complex. It demands certain mental attributes. The most essential is a veritable lust for truth. This has to be supported by skill in experimentation, accuracy in observation and record, correct interpretation of findings, and due appreciation of their significance. The lust for truth must result in active search which recognizes no sacrifice. Skill in experimentation

involves insight and ability in the selection and the carrying out of well-controlled experiments. Accuracy in observation implies capacity to see, a knowledge of the subject, and an appreciation of the phenomena observed. Accuracy of record demands precise and prompt notations, made preferably during the course of experimentation, for, as a rule, observations made to-day and recorded tomorrow are lost to science. Correct interpretations of findings and due appreciation of their significance demand a well-trained mind, critical judgment, and a familiarity with the subject in relation to contemporary science.

This may be stated in a somewhat different way. Investigation consists of four fundamental factors: (1) the clear conception of

the problem, that is, a definite "Fragestellung"; (2) the selection or development of methods capable of solving the problem; (3) ability to recognize relationships, to orient the problem to existing facts; and (4) accurate measurements and records.

The spirit of investigation is a living force, born within or rendered kinetic by contact from without, which, when first awakened, is usually feeble and requires cultivation, but when fully developed directs action and controls destiny. It is difficult to define, to understand, to acquire, to cultivate, and to communicate.

The cultivation and the diffusion of the spirit are our problems. Once the investigator is imbued with the spirit, investigations will proceed and bring results. But in diffusing, the spirit must be communicated so that it may be acquired by another. Consequently we must consider its acquisition as well as its cultivation and diffusion.

Acquisition of the Spirit of Investigation.The statements of Hippocrates relative to the attributes desirable in the student for instruction in medicine apply equally well to the prospective investigator. Hippocrates says:

Whoever is to acquire a competent knowledge of medicine ought to be possessed of the following advantages: a natural disposition, instruction, a favorable position for the study, early tuition, love of labor, leisure. First of all, a natural talent is required, for when nature opposes everything else is vain, but when nature leads the way to what is most excellent, instruction in the art takes place, which the student must try to appropriate to himself by reflection, becoming an early pupil in a place well adapted for instruction. He must also bring to the task a love of labor and perseverance, so that instruction taking root may bring forth proper and abundant fruit.

Instruction in medicine is like the culture of the production of the earth, for our natural disposition is, as it were, the soil; the tenets of our teacher are, as it were, the seed; instruction in youth is like the planting of the seed in the ground at the proper season; the place where the instruction is communicated is like the food imparted to vegetables by the atmosphere; diligent study is like the cultivation of the fields; and it is time