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under consideration, and a dispensary may be started for outdoor cases as an introduction to something on a larger scale.

16. Treatment of cases of Scarlet Fever by means of Specific Antitoxin. In recent years a considerable number of cases of scarlet fever have been treated with scarlet fever antitoxin.

It is regarded generally as a valuable therapeutic agent, diminishing the risk of dangerous complications and of death. Like diphtheria antitoxin, scarlet fever antitoxin should be administered early in the course of the disease.

C. CONCURRENT ACTIVE IMMUNISATION AGAINST DIPHTHERIA AND SCARLET FEVER.

17. Combined Injections.-The Aberdeen area appears to be the only centre in Scotland that has so far had experience of immunising against both diphtheria and scarlet fever by a single series of injection.

It was early apparent that there would be great practical difficulty in securing active immunisation of the population against diphtheria and scarlet fever unless immunity against both diseases could be secured at one and the same time by a combined inoculation.

Before making use of the combined prophylactic, experiments were made made on laboratory animals both by Dr. Smith in Aberdeen and by Dr. O'Brien of the Wellcome Research Laboratories in London to determine whether it might be safely used, and at the same time give a satisfactory immunising response. The immunising power of the mixture against diphtheria was found to be unimpaired in laboratory animals. Its immunising power against scarlet fever, however, could not be determined by animal experiment. There was no evidence of dissociation of the mixture, or of the production of specially toxic qualities on standing for a fortnight. The effect of the mixture on volunteers (medical students and nurses) was then investigated. It was found that it could be safely used, and that the immunising effect of the mixture was equal to that of the two immunising agents when used separately. The combined prophylactic is therefore now being used on a considerable scale in community immunisation in Aberdeen. Up to date (September 1926) 524 children, in the one to six years age-period, have received a first series of immunising injections of the combined prophylactic. Even when the preliminary susceptibility tests are eliminated, it is found in practice that mothers are reluctant to have their infants retested after the first series of immunising injections. For this reason, and in order to encourage the widest number of parents to secure this immunising device for their children, it has been considered advisable to delay the retesting of these children until they enter school at the age of five years.

School children are more sensitive to the injection of the

combined prophylactic than children in the 0-6 year age-period, and in school children preliminary Schick and Dick testings are desirable. A total of 1,305 school children who have been found to be Dick-positive and Schick-positive have received a first series of immunising injections of the combined prophylactic. Of these 1,305 children, 151 have been retested at the end of three months with the following results :—

Reaction to Dick Test.

121 of the 151 children, or 80 per cent., have been found to be Dick-negative;

16, or 11 per cent., have been found to be mildly Dickpositive; and

14, or 9 per cent., have been found to be markedly Dickpositive.

Reaction to Schick Test.

Some 82, or 54 per cent., have been found to be Schicknegative;

38, or 25 per cent., mildly Schick-positive; and

31, or 21 per cent., markedly Schick-positive.

Six of the children who had received a first series of immunising injections of the combined prophylactic and who had not been retested developed scarlet fever-1, two months later; 2, four months later; 2, six months later, and 1, eleven months later. Two developed diphtheria-1, three months later, and 1, eleven months later.

In the County of Aberdeen of those found both Schick and Dick-positive, 2,348 received prophylactic injections against both diseases, 559 receiving four, 1,688 three, 69 two injections, and 32 one injection.

D. GENERAL CONCLUSIONS.

18. Schick Testing and Immunisation against Diphtheria.Schick testing has been carried out on a considerable scale in Scotland, and also immunisation with toxin-antitoxin and with toxoid-antitoxin. No untoward effect has been noted.

In a number of cases diphtheria has developed at varying intervals after a course of immunising injections, but most of these cases arose within a few weeks or months of the last immunising injection, and probably before there had been sufficient time for the body to produce the necessary amount of antitoxin. A number of years will have to elapse before any opinion can be formed as to the efficacy of the methods of immunisation employed against diphtheria. The results reported from large centres of population in America are in favour of the procedure, and there is reason to expect that results. in Scotland will prove equally satisfactory.

19. Dick Testing and Immunisation against Scarlet Fever.The absence of an animal control makes the question of accurate dosage more difficult in the case of scarlet fever than in that of diphtheria. It is also questionable whether the immunisation obtained in scarlet fever is as lasting as that in diphtheria. Further experience will be necessary before any conclusion in favour of the present method of immunising against this disease can be adequately grounded. But some of the results obtained, especially in Aberdeen, are encouraging.

CHAPTER VII.

ULTRA-VIOLET RAY THERAPY.

1. Introduction.-Two years ago we issued a special report on the subject of "light" treatment, and in the last Annual Report reference was made to the value of ultra-violet irradiation in the treatment of rickets. Within the past two years an enormous amount of work has been done on ultra-violet ray therapy, both in this country and abroad, and numerous publications on the subject have appeared. Investigations into the action of the rays upon living cells, the human skin and other tissues, the cells, the platelets, the phosphorus and calcium content of the blood, bacteria, foods, &c. have been carried out by different workers. While many of the results are of clinical interest, we are yet largely in the dark as to the precise mode of action of ultra-violet rays. It seems clear, however, that ultra-violet radiation has an important effect upon mineral metabolism; it is therefore important that due regard should be had to an adequate supply of essential factors in nutrition, such as vitamins, mineral salts, &c. What was said in the above-mentioned report with regard to the general effects of irradiation has been fully borne out by subsequent experience, and the clinical results have been sufficiently numerous and striking to justify the conclusion that this particular form of treatment has come to stay. Its value is becoming more widely appreciated, and the sphere of its usefulness better defined.

The varying success that has attended its use, however, is sufficient to shew that, whatever its precise action may be, it is not a universal cure. On the other hand, the varying results in diseases in which its value is apparent would seem to indicate that the technique of its application is yet far from perfect. The results that different workers have obtained with what would appear to be the same type of case are difficult to explain. The factors involved in irradiation are really very complex. The intensity of the ultra-violet output from different sources varies from time to time, and these variations cause disturbances in the relative number of rays in different portions of the ultra-violet spectrum. Again the reaction of patients differs considerably according, it may be, to their pigmentation or to some unknown factor. Added to these are the questions of the time-exposure and its frequency. With so many variable factors, the difficulties of accurate administration will be appreciated.

2. Output of Lamps.-On practical grounds it appears desirable that close attention should be paid to the output of

lamps. While it is true that, in heliotherapy, good results are obtained with the varying amount of sunshine that is constantly taking place, yet as definite time-limits are essential in artificial irradiation, constancy of output is bound to be a factor of importance, and everything points to the desirability of the standardisation of lamps by some reliable and convenient method,

Two investigators at the Aberdeen City Hospital have shewn by means of the photo-electric cell that the output of ultra-violet rays in the open arc lamps, using either plain or impregnated carbon electrodes, is affected by variations in the voltage, and that the variations do not bear a direct relation to the changes in the voltage. Thus a 75 ampère arc working at 70 volts gave 70 units, at 80 volts 180 units, at 90 volts 245 units, and at 95 volts 253 units. It is stated that this variation probably arises from the fact that a stable arc is shorter at low voltage than at high; consequently there is less flame and greater shielding by the carbons. In a subsequent experiment the effect of increasing the length of the arc was tested while the watts consumed in the arc were kept as far as possible constant. The carbons were in line, and the output was measured from a point level with the arc, about 10 feet distant. The arc length was varied in five positions between the extremes of 3.4 mm. and 17 mm., and the ultra-violet output in the shortest arc was 14 units and in the longest 36 units.

They also demonstrated that a single long flame arc emits as much ultra-violet radiation as several lamps connected in series when precisely the same amount of current is consumed from the main.

But output is affected by other things besides the voltage and the length of the arc. The nature of the electrodes is also important. Plain carbons give off fewer ultra-violet rays than carbons cored or impregnated with suitable metals. The so-called white light carbon-an impregnated carbon- is very popular, but unless the electrodes used are always of similar make it is important that the output of new batches should be tested by some reliable method.

Dr. Johnstone, Hairmyres, carried out a series of tests on different carbons and in varying combinations, using the LevyWest pastille as his gauge. He used plain, tungsten-cored, nickel-cored, and polar white flame carbons. The best results were obtained by using a polar white flame carbon as positive and a plain carbon as negative. In every case the lamps consumed 15 ampères, and the pastille was exposed for two and a half hours.

The output of mercury vapour lamps also varies, but differs from the open-arc in that the variation is partly due to devitrification of the quartz container and partly to the deposition of globules of mercury on the inside of the burner. According to tests carried out by the investigators at Aberdeen City Hospital, the vacuum lamp when new has an intensity about four times

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