1. Scarlatinal streptococci obtained from the throats of cases of scarlet fever can be divided into various groups by means of agglutination and absorption tests. The same type of streptococcus can on occasion originate at least five separate clinically distinguishable diseases, namely, scarlet fever, tonsilitis, erysipelas, puerperal fever, and broncho-pneumonia, and it would appear that, so far as streptococcic infections are concerned, the nature of the disease entity is determined by the toxigenic qualities of the type of streptococcus, by the susceptibility or insusceptibility of the individual as determined by the absence or presence of the specific antibodies in the blood, and by the site of the infection itself (see p. 330).

2. Strong corroboration for the view that the S. scarlatinae is the causal organism of scarlet fever is obtained from the following findings, viz.:

(a) S. scarlatinae have been isolated from the throat brushings of practically all acutely ill scarlet fever patients (see p. 329).

(b) The whole clinical picture of scarlet fever going on to marked desquamation is produced by the subcutaneous injection of the exotoxin derived from the S. scarlatinae, the exotoxin having been haeated to 55° C. for one hour, with a view to destroying any filterable living virus which might be associated with the filtered exotoxin (see p. 342).

(c) In the Schultz-Charlton reaction the blanching of the scarlet fever rash is caused by the serum of a horse immunised against S. scarlatinae and its toxins.

(d) Dick-positive and Dick-negative reactions as produced by the intradermal injection of the streptococcus toxin have the closet correspondence to the degree of susceptibility or immunity to scarlet fever of the respective reactors (see p. 334).

(e) Susceptible nurses once they are actively immunised by injections of scarlatinal streptococcus toxin have been shown to be immune to the toxin of scarlet fever (see p. 337), and susceptible school children similarly inoculated are likewise immune (see p. 338).

(f) Return cases of scarlet fever can be prevented by actively immunising susceptible contacts with scarlatinal streptococcus toxin prior to the scarlet fever patient being discharged from hospital (see p. 339).

(g) Susceptible contacts can be safeguarded from taking scarlet fever by passively immunising them with a sufficient does of antistreptococcus serum obtained from a horse wich has been immunised by injections of S. scarlatinae and its toxin (see p. 349).

3. The limitations of the Schultz-Charlton reaction as an aid in the diagnosis of scarlet fever have been confirmed (see p. 330).

4. Evidence has been obtained which firmly establishes the value of the Dick suseptibility test as a measure of susceptibility to scarlet fever (see p. 332).

5. Extensive corroboration of the value of the Schick test as a measure of susceptibility to diphtheria has been obtained (see p. 334).

6. The efficacy of active immunisation against scarlet fever by means of scarlatinal streptococcus toxin injections has been demonstrated by the fact that, while scarlet fever has been present in epidemic form in Aberdeen, no nurses or maids in Aberdeen City Hospital have contracted scarlet fever since June 1st, 1925, from which date the nursing and domestic staffs of the hospital have been actively immunised before being admitted for duty to the scarlet fever wards; whereas, prior to that date, an average of 8·5 nurses, or 9·5 per cent. of the nursing staff, and 1·4 maids, or 4·2 per cent. of the domestic staff. annually suffered from scarlet fever (see p. 337).

7. Coincident with the disappearance of scarlet fever in the immunised nursing staff of the City Hospital, there has been a notable increase in the incidence of streptococcic tonsilitis in these immunised nurses, and the streptococci obtained from these cases of tonsilitis in nurses commonly fall into one or other of the serological groups of scarlatinal streptococci; and accordingly it would appear to be proved that immunised nurses, while protected by immunisation from the toxic effects of the exotoxin of S. scarlatinae, are not protected against tonsilitis due to S. scarlatinae (see p. 338).