using 0.25 per cent. NaCl solution and adding urea in one instance and aminoids, Biuret free, in another, to make the solution about isotonic with blood serum. Blood serum and starch were also added to some of the tubes. The results of culture experiments were invariably negative in the urea tubes. Growth was occasionally noted in the aminoids, but transplants were unsuccessful.

Successful results were finally secured by using the method of Barret and Yarbrough (1921) with a modified Ringer's solution instead of 0.5 per cent. NaCl. The latter contained: NaCl 6.5 gms., KCl 0.14 gms., CaCl, 0.12 gms., NaHCO, 0.20 gms., Na,HPO, 0.01 gms., per liter of distilled water. The ingredients were weighed from C. P. crystals on an analytical balance but no attempt was made to desiccate them before weighing. The freezing points of various solutions thus far used have ranged from minus 0.52° C. to minus 0.58° C. Eighteen cc is pipetted into clean test tubes and autoclaved. Two cc of human or horse serum is then added, plus a sprinkle of sterile rice starch. Pig serum has thus far proved unsatisfactory. A solution made from Loeffler's dehydrated blood serum is used frequently instead of the human or horse serum. This product is manufactured by the Digestive Ferments Company, of Detroit, Mich. The contents are listed as beef blood 3 parts and dextrose broth 1 part. Solution is obtained by adding 8 gms. of the powder to 100 cc of distilled water at 40° C. It is advantageous to measure the water in a 250 cc flask containing a few glass beads and sterilize. Shaking the flask with the beads aids in securing solution, but even so there is much suspended matter. A culture of Balantidium from the pig was maintained for fifty-four days and was still thriving on April 4. The tubes are kept in an incubator at 36° C. and transplants are made according to Barret and Yarbrough's technique. Twenty transplants have been made. They are made usually at three-day intervals, but on one occasion (7th transplant), a seven-day interval occurred. Trophozoites in abundance have been found on a number of occasions at the end of seven days; but they usually decrease rapidly after three days.

Twelve attempts have been made to secure pure lines by isolating single individuals. The findings agree with those of Barret and Yarbrough that this can not be done by the drop culture method. The organisms appear to be anaerobic. Success was obtained by picking out single individuals with a micropipette, placing into a drop of culture fluid on a cover slip and dropping the latter into a test tube containing the medium. On one occasion multiplication occurred but the transplant failed.

After three unsuccessful attempts a culture was started with Balantidium from the guinea-pig in the same media as are used for the culture from the pig. This strain has now been successfully transplanted six times. The organisms ingest starch as does the pig Balantidium and become very active. It would be impossible to distinguish the trophozoites from those from the pig if the labels were left off the culture tubes. Occasional cysts have been found in tubes in which trophozoites from the guinea-pig have disappeared. Despite repeated research no cysts have been found in cultures from the pig.

RESISTANCE OF TROPHOZOITES TO HYDROGEN SULPHIDE

The odor of H2S is always pronounced in the feces of pigs. On five occasions this gas has been bubbled through culture tubes for fifteen to thirty seconds. No deleterious effects have been noted on the trophozoites. The first time that the experiment was tried the culture from the pig lived seven days. It was hoped that this gas might be used to check the growth of harmful bacteria. Subsequent results were SO variable that no conclusions are justified. H„S was found toxic to the trophozoites when bubbled through feces of the pig; when treated and untreated samples were kept in the incubator the organisms disappeared in forty-eight hours from the treated tubes but lived seventy-two hours in the untreated material.

SUMMARY

It has been shown that trophozoites of balantidia from the pig are normal in appearance and reactions when the medium is cooled to room temperature. They may live at room temperature for ten days. Trophozoites that infect the pig may pass through the stomach of the guinea-pig and reach the cecum, where they are normal after eighteen hours. Trophozoites are frequently passed in feces by the pig but cyst production is irregular and determined by unknown factors as in monkeys, guinea-pigs and man. The fluid of pig feces from the cecum is slightly hypertonic to blood serum. The method of Barret and Yarbrough for the cultivation of Balantidium coli has been found practicable for Balantidium from the pig and guinea-pig. The addition of rice starch improves the medium and Ringer's solution without dextrose was found more suitable than 0.5 per cent. NaCI solution. Loeffler's beef blood serum may be substituted for human serum or horse serum. H.S appears non-toxic to Balantidium from the pig when passed into culture tubes.

THE JOHNS HOPKINS SCHOOL OF HYGIENE AND PUBLIC HEALTH

C. W. REES

The object of the present work was to find the reason for the intensification of latent image. In the course of it, certain possible underlying mechanisms suggested themselves.

It was the work of Bray and Livingston3 on the catalytic decomposition of H2O, in solutions containing H and Br ions which gave the first possible clue as to such a mechanism. They showed that prior to a steady state, which may require an hour or more in being reached, the following reactions take place when acid and soluble bromide are mixed with H2O2 solution:

(3)

2 H2O2 = 2 H2O+02 Soluble bromide is present in practically all ordinary dry plates, and in all the previous work on latent image intensification acid was present in the solution of H2O2 used.

The second possible clue to an explanation of the action was a chemical mechanism of latent image formation recently proposed by K. C. D. Hickman.* He has obtained evidence that while in bulk, in a test tube, Br in water solution reacts quantitatively with Ag2S to give AgBr, H2SO, and HBr, in the photographic plate on the other hand, when the Ag2S is isolated in the so-called sensitivity specks5 and the Br is formed only in very limited quantity,

4

1 Presented at the meeting of the American Chemical Society, Philadelphia, September, 1926.

2 E. P. Wightman and R. F. Quirk, J. Franklin Inst. 203, 261 (1927).

8 W. C. Bray and R. S. Livingston, J. Am. Chem. Soc. 45, 1251 (1923); R. S. Livingston and W. C. Bray, Ibid., 45, 2048 (1923); R. S. Livingston, Ibid., 48, 45 (1926). 4 K. C. D. Hickman, Phot. J. 67, 34 (1927).

5 S. E. Sheppard, Colloid Symposium Monograph 3, 76 (1925); Phot. J. 65, 380 (1925).

W. Clark has contended that the action of H2O2 in producing latent fog on a photographic plate is purely chemical and not one of chemiluminescence as previously supposed by Sheppard and one of us." The present hypothesis and experimental work, while they do not disprove the chemiluminescence view, do furnish the basis for a chemical explanation of H2O2 action.

An additional experiment which supports the chemical view is that if we remove almost all the

VOL. LXVI

JULY 29, 1927

No. 1700

CONTENTS

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BONDS OF UNION BETWEEN TROPICAL MEDICINE AND GEN

ERAL MEDICINE1

It is my wish that my first greeting and that my parting words should express my appreciation of the honor and the pleasure of visiting you here in Porto Rico. It is distinctly profitable to me to have this opportunity of exchanging ideas and experiences with you in our chosen field of work. In arranging for our conference this evening Dr. Lambert wrote to me suggesting that my talk ought to have a title, and he even ventured to hope that this idea would not come as too much of a surprise to me. So I have selected a subject that will permit us to wander where fancy leads, perhaps, who can tell, to one or two unexpected developments.

Our crowded activities grant us but little time for reflection, and it is easy to overlook points of contact between the adjacent fields such as tropical and general medicine. Inevitably, these two fields have exerted a profound influence on each other.

Strangely enough, the conception of tropical medicine is rather foreign to many individuals in the profession at home. The very name sometimes tends to frighten people away. To a few, it represents merely a curiosity, interesting but unimportant. One of your obligations will be to arouse still further the interest and support in New York City of your work here. One summer I met an elderly physician who had spent his life travelling in the tropics. He said to me: "Mercy, no, I stay on the ship. I never look at those patients ashore. Why should I clutter up my head with all that nonsense? If I ever had to treat those diseases I'd go somewhere and take a month's course in the subject." A few of the more serious minded deceive themselves into thinking that tropical medicine represents a real opportunity to make distinctive discoveries of new etiologic agents and new and important clinical entities almost without effort. Sometimes I feel that my friends almost take it to heart that the generosity of nature in tropical lands should cheat industry and so rudely violate the stern principles of no reward without great labor.

1 A popular address delivered on February 22, 1927, as visiting lecturer at the School of Tropical Medicine, University of Porto Rico, San Juan, Porto Rico.

Suppose, however, that we want to choose as a model a disease of extremely intricate nature, the details of which have been worked out with exactness. It is best to turn to the tropics for an example. In the etiology of malaria we have not one but three distinct parasites very closely related; however, to the eye of the protozoologist they are readily distinguishable. The transmission of the disease from patient to patient is a complicated process. The sexual forms of the malarial parasite come into prominence. They leave their intermediate host, man, to take up a cycle of development in their definitive host, certain species of mosquito. After the completion of this cycle the mosquito is ready to set up new infections in man. The pathology of the disease is well-nigh completely understood. The diagnosis in patients is reasonably exact. The treatment, though not perfect, is marvelous compared to that of many bacterial infections. Lastly, prophylactic measures, though difficult, are quite feasible. The antimosquito campaigns have been enormously facilitated by Marshall Barber's ingenious introduction of Paris green for combating larvae.

We look to Sir Patrick Manson and to the British nation as the founders of tropical medicine. They took advantage of their natural opportunities. Great Britain with her extensive possessions has many physicians employed in foreign service and they all come back to one spot. The conditions in the United States are very different. We have only a few men who go to the tropics and they come home to scatter across a broad continent. A corresponding difference applies in the two countries to patients who are invalided home. With us, this works to the disadvantage both of the patient and of the subject of tropical medicine. In the absence of the incentive of stern necessity, interest has been intermittent and the development of the subject has been slow and arduous in the United States. When I wanted to learn something of the scope of your new undertaking I turned not so much to the American medical journals for information but to the literature from Great Britain. There have been some exceptions to this general lack of interest at home. Occasionally some of our institutions have devoted a number of years of work and considerable sums of money to purely tropical problems, meanwhile carefully avoiding any permanent responsibility in this field. There seems to be a willingness to profit by special opportunities arising in the field of tropical medicine accompanied by an unwillingness to offer continuous support to the necessities of the daily routine in this subject.

Clearly we can not model our schools after the British pattern. We must find somewhere compensating advantages in our own circumstances. Here

The finger of erudition is often pointed at the term "tropical medicine." Some medical men seem to feel that they have fathomed the mysteries of this term when they learn that workers in the tropics have frequently made the statement that there is no such subject as tropical medicine. In one sense, I agree with this. Admittedly the phrase is one of convenience rendered necessary by the geographical = separation of diseases. But the distinction is justified on scientific grounds. Fascinating fundamental principles are found in tropical medicine for which no counterpart exists in the diseases prevalent in cold climates. Thus, for all intents and purposes, the insect hosts of disease and even the protozoan infections take no real part in the life of the student of medicine in the temperate zones. Let me assure you, it is a difficult matter to find a satisfactory phrase for differentiating the medicine of cold climates from that of the tropics. "Internal medicine" does not help greatly. Largely in a complimentary sense I have been using the expression "general medicine." In so far as general medicine permits itself to forego the subjects of protozoology and entomology, it becomes an important branch of the larger field of medical sciences.

Well, this ought to convince you of my warning that we might be tempted to wander from any fixed topic. I will not in any way attempt to sum up the more striking achievements of tropical medicine but will emphasize only those features in which this subject and general medicine have exerted an influence upon each other. Indeed, as already indicated, we must close some of the most brilliant pages of medicine.

In my judgment, the most fundamental influence that tropical medicine has exerted in the field of medical sciences is to be found in the discovery of vitamins and the group of diseases sometimes designated as avitaminoses. You remember when we studied medicine, not so very long ago, beriberi was classed among the specific infectious diseases, with the reservation that some unknown toxin might play a more or less decisive rôle. We now know that neither of those factors plays any part whatever. The clinical and epidemiological data seemed at times in the past to offer almost convincing evidence of

the infectious nature of this disease. Many striking incidents occurred in a manner almost suggestive of some conspiracy in nature to conceal the facts. For example, a ship with its crew in apparently good health would call at a port where beriberi prevailed. Then after some days the disease would, so to speak, "break out" among the crew. Furthermore, if a mother suffering from beriberi nurses her own child she becomes a serious menace to the health of that child. Such children are prone to develop beriberi in an acute form that terminates suddenly in death. But the Dutch investigators knew and had known for many years that beriberi was due simply to lack of proper nourishment. This discovery was made by Eijkman in 1890. There is an incident of a very human nature connected with Eijkman's production in chickens of experimental beriberi or, more accurately, polyneuritis. At the time he was not working cn beriberi at all and chickens are very likely the last animal that he would have selected for the study of beriberi. The incident, as it was described to me, occurred in this manner. The animal quarters for these experimental chickens lay at a little distance from the laboratory alongside the hospital building. Very unexpectedly, the chickens developed polyneuritis to such an extent that the investigations that were in progress were seriously threatened. So Eijkman courageously decided that it was important to find out the cause of this polyneuritis. Then, to his surprise, the chickens promptly recovered so he was obliged to go back to his original problem only to be interrupted again by the recurrence of polyneuritis. Many observers would very justly have felt discouraged at this point. But Eijkman with remarkable skill succeeded in unravelling a mysteriously intricate network and revealed a clear chain of events occurring in logical sequence. The denouement came in this manner. In the hospital the patients were served with polished rice. For the protection of the patients, a rule was in force that any rice left on the patient's plates must be thrown out. In the laboratory the animal boy was given a small sum of money for the purchase of the cheaper unpolished rice for the experimental chickens. Now the Malays are very kindly in their disposition and the laboratory boy had a good friend among the orderlies in the hospital. It does not require much imagination to see that it was easy to provide a handsome diet of polished rice from the hospital for the chickens in the animal house nearby. There was no need wantonly to squander these valuable funds supplied for the purchase of unpolished rice. Now by mere coincidence, it happened that after the first outbreak of polyneuritis appeared, the orderly in the hospital went on vacation and the laboratory boy went back

to feeding unpolished rice. The symptoms disappeared and the animals recovered with mysterious rapidity. Then when everything was going nicely, the orderly returned to the hospital and the chickens resumed their diet of white rice and with it the symptoms of beriberi returned.

Looking back at this distance, everything is beautifully clear. There is some strange substance in rice bran, in various grains, and in many other foods which is necessary for normal nutrition; in the absence of this substance polyneuritis develops. Eijkman picked his way with remarkable accuracy through this complicated maze in the face of many conflicting theories about beriberi. His conclusions were promptly rejected. The rest of the world said, "Oh, no, it just can't be true!" Twenty years later several investigators had the very happy thought of trying it. They made a discovery. They found that it is true. There is no flaw in Eijkman's experimental data, though his interpretation has subsequently undergone some revision.

Beriberi is not uncommon in the Philippine Islands. The Filipinos offered information to the profession which was not utilized. Patients under treatment sometimes reported that they could cure themselves with a diet of a certain native bean. Not knowing the facts about beriberi at this time, we explained to them very kindly the error of their ways. They accepted our explanations with gratitude and continued in their superstitious practice. Their confidence was not misplaced, that is, their confidence in dietary measures was justified.

Barely a quarter of a century after Eijkman's first publication, the physiologists began an accurate investigation of the requisites of a balanced diet. The first steps were difficult. It was necessary to give up some old established comfortable views. Proteins, carbohydrates and fats with a little salt and water had long been regarded as an adequate bread of life. Now it was rather disturbing to have to admit that some utterly unknown substance, even in minute quantity, exerts a powerful influence and is an essential item in our daily diet. Funk used the term vitamin to designate this substance which prevents the development of beriberi. As the interest in this phase of nutrition increased, other vitamins were discovered. Recently one has been described by Evans in California which is concerned not with ordinary nutrition but with the process of reproduction. In the field of medicine investigators naturally sought to explain other diseases on the basis of a dietary deficiency. It had long been known that scurvy is relieved by lime juice. Work of outstanding importance was accomplished by Goldberger in pellagra. Now in beriberi the problem is relatively simple; in