Since the original definition of the coli-aerogenes group of organisms by MacConkey (1905,1909), research has been continually directed in an endeavour to find a more rapid and definite distinction between its respective members.

In general, for the purposes of water analysis, the conform organisms can be divided into two main groups: faecal coli, of which Bact. colitype I can be considered the typical member, and the non-faecal organisms comprising the intermediate-aerogenes-cloacae (I.A.C.) organisms. All available evidence tends to show that Bact. colitype I is by far the most frequent organism in the human and animal intestine. Levine (1921) has summarized the figures of various workers and obtained a percentage ratio of 93·4:6·6 as the ratio of coli:aerogenes in faeces, while Bardsley (1938) has shown that in only a very few cases does the number of I.A.C. organisms exceed the faecal coli in faeces.

1. The agglutination titres for sheep and for horse erythrocytes of 100 normal sera and twenty-seven glandular fever sera have been determined.

2. The results of the sheep-cell agglutination tests on normal sera differed considerably from those of Stuart, Burgess, Lawson & Wellman (1934) whose technique was used. The reason for this difference was not determined. It was thought to have some bearing upon the interpretation of sheep-cell agglutination tests in the diagnosis of glandular fever.

3. Although in the glandular fever sera the horse-cell titre was usually higher than the sheep-cell titre, the normal range for horse cells was also higher, and in the diagnosis of glandular fever there did not appear to be any advantage in using horse cells instead of sheep cells.

4. The value of absorption tests in the diagnosis of glandular fever is discussed and a new technique described which has practical advantages over other methods although it does not embody any important new principles.

5. Of 300 normal sera examined by this technique, five contained small amounts of an antibody indistinguishable from glandular fever antibody and ten others contained a sheep-cell agglutinin apparently, though not certainly, different from any yet recognized in human serum.

6. A comparison of the results of the two tests on thirty-one samples of glandular fever serum showed the absorption test to be a more sensitive diagnostic test for glandular fever than the ordinary sheep-cell agglutination test.

In a large institution whose population can be considered as forming a semiclosed community there frequently exist conditions favourable to the spread of infectious diseases. The organization of such an institution to avoid epidemics is an accepted difficulty of administration. The occurrence of an epidemic in a semi-closed community offers opportunity for thorough investigation, and is, therefore, of more than usual interest.