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six months and under five years of age are immunised without preliminary Schick testing. Those over five years of age are Schick-tested and reactors immunised. The clinic is attended mainly by contacts of notified cases.

(4) A few children attending the Child Welfare Centres have been immunised.

(5) Medical practitioners, if they so desire, are supplied with .material for Schick testing and immunisation by the Public Health Department; but so far the demand has been small.

(6) Infants over six months old under treatment in the Dundee Infant Hospital are immunised.

(b) Number of Tests and Results.-In 1926 the number of Schick tests performed in Dundee was 1,404. Of that number 17 did not return for inspection. The following table gives a record of the results in the remaining 1,387 :—

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Ten of the 667 persons who gave a positive Schick reaction contracted diphtheria at a later date.

(c) Immunisation against Diphtheria. -Immunisation by three injections of 1 c.c. of toxin-antitoxin at intervals of a week was performed in 1,084 persons. Of the 667 persons who gave a positive Schick reaction 596 were immunised, while 488 persons, mainly children under five years of age, were immunised without a preliminary test of susceptibility. The numbers immunised in various age groups are shewn in tabular form below:

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Among the 667 positive Schick reactors 71 the course of three immunising injections. injections were given, in 13 one, and in 19 two immunising injections were given.

Among the 488 not previously Schick-tested 18 received one and five received two immunising injections, while 465 received the full course of three immunising injections.

(d) Diphtheria among those who had received a complete course of three injections.-Of the 1,084 persons who were immunised, 14 were later suspected to be suffering from diphtheria.

Two of these shewed no evidence of the disease, either clinically or bacteriologically. Six were considered to be temporary carriers. The remaining six were all accepted as cases of diphtheria, the suggestive clinical evidence being confirmed bacteriologically. The time that elapsed between the last immunising dose and the onset of illness varied as shewn below:

Case 1. Aged 3 years. Very mild; notified three months and 24 days after last immunising dose.

Case 2. Aged 6 years. Very mild; notified one month and eight days after last immunising dose.

Case 3. Aged 2 years. Mild; notified four months and eight days after last immunising dose.

Case 4. Aged 4 years.
last immunising dose.

Case 5. Aged 15+ years.

Moderate; notified ten days after

Moderate; notified six months

and four days after last immunising dose.

Case 6. Aged 15+ years. Very mild; notified four months after last immunising dose.

Nos. 5 and 6 were nurses on the staff of King's Cross Hospital. While all six were accepted for purposes of treatment as cases of diphtheria, only two (Nos. 4 and 5) could be considered as undoubted cases of the disease, and one of these (No. 4) sickened ten days after the last immunising dose of toxinantitoxin, too early to expect any immunising effect.

8. Aberdeen County.-The following information as to the testing and immunisation of those found susceptible to the Schick test in Aberdeen County is provided by Dr. Rae, County Medical Officer of Health. Those tested were mainly school children, but adult girls in a training school, nurses and attendants in a mental hospital, and nurses at one of the Infectious Diseases Hospitals in the County were also tested and, if found susceptible, immunised. The period during which the work recorded was done was between November, 1925, and the end of December, 1926. Of a total of 4,711 Schick tests, 3,647 were read as positive and 1,064 as negative. Of the positive reactors, 1,240 received injections of diphtheria prophylactic, 149 receiving four injections, 1,061 three, 20 two, and 10 one injection.

Three cases immunised against diphtheria had, up to the end of 1926, been notified as suffering from the disease, one having developed the disease a week, a second three weeks, and the third 6 months after the third immunising doses. The last was seen by one of the staff of the Medical Officer of Health and regarded very definitely as not one of diphtheria.

B. SCARLET FEVER.

9. The Dick Test of Susceptibility to Scarlet Fever.-Up till

a very recent date the causal organism of scarlet fever remained unrecognised, but in 1923 and 1924 the Drs. Dick, in America, published the results of their work, including the results of the inoculation of human volunteers with the organism which they had isolated from cases of scarlet fever and grown in pure culture. As a result of their work scarlet fever is now universally regarded as a result of infection with a hæmolytic streptococcus, of which more than one strain has been distinguished. As in the case of diphtheria, it has proved possible to inoculate horses and to obtain from them an antitoxic serum of considerable potency which is now largely used in the treatment of cases of scarlet fever. The Dicks have also devised a skin test of susceptibility to scarlet fever which is similar to that associated with Schick's name in the case of diphtheria.

Owing to the insusceptibility of lower animals to the toxin of the scarlatinal streptococcus, it has not been found possible to use them for standardising this product as is done in the case of diphtheria toxin. The use of the human skin test dose as a measure of the strength of scarlatinal streptococcus toxin is accordingly necessary. The difficulty of determining an exact standard of toxicity is a great handicap to the bacteriologist and clinician alike.

As in the case of the Schick test, experience of the Dick test in Scotland has been limited to a few areas, and it is proposed to give a brief account of the experience in each area.

10. Aberdeen.-In the Dick test as practised in Aberdeen City Hospital, 0-2 c.c. of a dilution of the soluble toxic filtrate obtained from a broth culture of the scarlatinal streptococcus is injected intracutaneously into a flexor aspect of the left forearm. At the same time a control test with diluted toxin, which has been inactivated by heating in a water bath at 100° C. for one hour, is made on the flexor aspect of the right forearm. By examining the "test" and the control," it is possible to differentiate four distinctive reactions, viz. the positive, the negative, the negative-pseudo and the positive combined.

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(a) The positive Dick reaction develops in six to twelve hours as a light red flush, and it reaches its maximum in 24 hours, shewing a circumscribed area of redness with slight infiltration measuring from 15 to 30 mm. in diameter. This positive Dick reaction at the end of 24 hours closely resembles the positive Schick reaction which has reached its maximum intensity on the fourth day. The Dick reaction fades more rapidly, and only the strongly positive reactions shew a slight brownish pigmentation at the end of seven to ten days.

(b) The negative reaction shews no change at the site either of the test or of the control.

(c) The negative-pseudo reaction shews the same appearance in the test and control. These reactions are due to a hypersensitiveness of the individual to the foreign proteins in the test and control fluids.

(d) The positive-combined reaction represents a combination of the positive and negative-pseudo reactions. The reaction in the test with the unheated toxin is more pronounced than in the control with heated toxin.

The positive and positive-combined reactors are susceptible to scarlet fever; the negative and negative-pseudo reactors are presumed to be immune to the toxic effects of the scarlatinal streptococcus.

It was, however, observed in Aberdeen that the intensity of the Dick reaction is of much significance, and that scarlet fever occurred only in individuals who shewed a marked Dick reaction. The conclusion drawn from this is that numerous individuals regarded at present as susceptible will later be eliminated when further investigation has been made of the immunity mechanism in scarlet fever, and when a method of more accurate standardisation of the toxin has been evolved.

(e) Susceptibility to Scarlet Fever according to Age Period. -The Dick test of susceptibility to scarlet fever was carried out in the same 1,500 people in whom the susceptibility to diphtheria had been investigated by means of the Schick test. The degree of susceptibility to scarlet fever as estimated by the Dick test is remarkably similar to that of the susceptibility to diphtheria as estimated by the Schick test. Thus, in the period from 0-5 years, 96-4 per cent. gave a positive Dick reaction; in the age-period 5-10 years, 81-2 per cent.; in the age-period 10-15 years, 65.5 per cent.; in the age-period 15-20 years, 60.8 per cent.; and in the age-period 20-25 years, 52-4 per cent. gave a positive reaction.

(f) Susceptibility according to Social Conditions.-In westend schools it was found that out of 718 tested, 562, or 78.3 per cent., were Dick-positive; out of 392 middle-class school children, 231, or 590 per cent.; and out of 404 east-end school children tested, 118, or 29.2 per cent., were Dick-positive. These proportions are also remarkably similar to those found in the case of the same children tested for susceptibility to diphtheria.

(g) Susceptibility to Scarlet Fever of Persons who gave a History of having formerly suffered from the Disease. It was found that of 121 persons who had formerly suffered from scarlet fever, 13 individuals, or 10.7 per cent., proved Dick-positive.

(h) The Dick Susceptibility Test in Cross-infected Wards.Further evidence of the value of the Dick test as a guide to the susceptibility of individuals was obtained by testing patients in wards in which cross infection with scarlet fever had taken place, or in wards to which cases of scarlet fever had been accidentally admitted. In this way scarlet fever was observed to occur in 21 patients who previously shewed a positive Dick reaction. On the other hand, numerous cases, notified as scarlet fever, were admitted to the scarlet fever wards of the City Hospital with no definite clinical sign of the disease, and when found to be Dick-negative were allowed to remain in contact with other scarlet fever cases. In no case did any of these

patients develop scarlet fever. In seven instances cases were admitted to hospital in the third or fourth week of illness with a definite desquamation and all the appearances of having had a typical attack of scarlet fever. The Dick test in all seven cases was markedly positive on admission, and all developed a second attack of the disease. In several cases in which the Dick test had been carried out two or three weeks prior to the attack of scarlet fever, the area on the forearm corresponding to the previous reaction again became intensely red as compared with the rash on the surrounding skin.

(i) Prevention of Scarlet Fever by Active Immunisation with Scarlatinal Streptococcus Toxin.-Lower animals cannot be used to standardise scarlatinal streptococcus toxin, and before beginning an immunising campaign among patients in hospital or in the community generally, it was necessary to carry out an extended series of inoculations on volunteers before being satisfied that the toxin that was to be employed was stable, that in the doses selected it was relatively non-toxic, and that it produced a sufficiently permanent immunising response. In Aberdeen, Dr. Kinloch found numerous volunteers among medical students and the members of the nursing staff at the City Hospital who offered themselves freely for the preliminary inoculations. Thus, in one of the series of preliminary experiments, six susceptible individuals were each given as a first immunising injection the equivalent of 500 skin doses of a toxin, one skin test dose of which had previously been found to give good positive reactions in susceptible children and negative reactions in convalescent cases of scarlet fever. Within twelve hours of receiving the equivalent of 500 skin doses, three of the individuals had marked swelling and induration at the site of the injection, accompanied by pyrexia, malaise, headache and vomiting; while in the other three, swelling and induration of the arm alone were noted. This experiment indicated that the amount of the toxin was excessive for immunising purposes, and that further dilution of the toxin was necessary.

At the same time it was obvious that it was of the utmost importance that the toxin should be of sufficient strength to produce a permanent immunising response. Thus, when a

weaker toxin was substituted for the stronger toxin, which produced the constitutional disturbances above described, three of the second series of six cases that had become Dick-negative reactors within a fortnight of the third injection were found to have become Dick-positive two months later. It was thus necessary to use the strongest toxin that would be tolerated. without producing a general disturbance in the majority of susceptible individuals. In practice it was found that a toxin, 500 skin test doses of which produced a general erythema in about 3 per cent. of the inoculated individuals, met this requirement. The appearance of this erythema following on the first immunising injection of 500 skin test doses does not contra-indicate the two remaining injections of 1,000 and 3,000 skin doses respectively

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