The question of the complexity of immune bodies and of complements can be best illustrated by bringing forward certain experiments of Ehrlich, who has always held to the multiplicity of both substances. These experiments have, like the former, to do with haemolysis.

1. The principle cause of post-scarlatinal diptheria is the admission into the scarlet fever wards of patients who, whether suffering from clinical diphtheria or not, are carriers of virulent diphtheria bacilli.

2. In large centres of population, where diphtheria always exists, diphtheria bacilli are to be found in a not inconsiderable proportion of school-children. In the absence both of evidence of clinical diphtheria and of a history of exposure to that affection, the bacilli are, in the majority of cases, of the non-virulent or saprophytic type and of little hygienic importance; in cases, on the other hand, where the clinical supports the bacteriological examination the bacilli are almost certainly virulent, and therefore dangerous; while in cases where the patient is known to have been exposed to infection the chances are great that the organisms are of the pathogenic variety, and such cases should always be regarded with grave suspicion.

3. On account of the prevalence of the non-virulent bacillus and the fallacies of single cultures, it may be doubted whether a routine bacteriological examination of throat and nose of all patients on admission would prove of sufficient value to repay the labour involved. Chief reliance must be placed on a careful inspection on admission, not only of the throat, but also of the nasal cavities, bacteriological examination being resorted to in cases of doubt.

4. In eradicating infection from an invaded ward bacteriological methods are, on the other hand, of prime importance, since children with apparently healthy throats and noses are often found to have acquired the virulent bacillus. An attempt to stamp out any outbreak of diphtheria by bacteriological examination of the throat alone is, however, futile, owing to the frequent infection of the nasal cavities.

5. Fibrinous rhinitis, which appears to be a not infrequent, though often unrecognised, affection of children is a common form of postscarlatinal diphtheria.

6. Although the treatment of diphtheria in the same hospital has no appreciable influence on the incidence of this complication of scarlet fever, it is advisable that precautions should be taken lest nurses harbouring diphtheria bacilli carry infection from the diphtheria to the scarlet fever wards.

7. To limit the risk of exposure to infection many-bedded wards should be avoided, and the mixing of patients from different wards prevented.

The use of neutral-red culture media has recently been suggested for the detection of B. coli in water supplies. Rothberger (1) grew a number of organisms on media containing various organic dyes, and found that while some species were able to bring about a reduction of the colouring matter in the medium, others produced no change. This difference in reaction was particularly marked in the case of B. typhosus and B. coli in media containing neutral-red. B. coli casused the reduction of the neutral-red to yellow with green fluorescence, whilst B. typhosus produced no change of colour beyond an occasional fading of the red. After testing a number of races of B. coli and B. typhosus, Rothberger proposed neutral-red media for the differentiation of the two organisms. Scheffler (2) confirmed in the main the work of Rothberger, and further observed that the reaction is by no means specific for B. coli. In addition to a number of bacterial species not commonly found in water, which gave the reaction, Scheffler found 3 of 13 organisms in spring and river waters, and 8 of 18 intestinal organisms from man which, though not belonging to the colon group, gave the neutral-red reaction.

Of late years the bacteriological examination of water has become of greater importance in routine work and more widely employed. With this development it has become increasingly apparent that the mere number of organisms present in a given quantity of water, though of considerable value, is liable to cause many fallacies of solely relied upon.

It was not possible to complete the considerable amount of work necessary for the following Addendum in time for inclusion with the article which appeared in the last number of this Journal.

That many epidemics of enteric fever have been caused by contamination of central water-supplies is beyond dispute, but evidence is accumulating that makes it difficult to attribute its widespread prevalence in endemic form in India and elsewhere to this cause. It is necessary, however, to guard against assuming that therefore the disease is not water-borne. There are in India innumerable chances of water, when stored for domestic use, being contaminated, besides the same possibility in the case of food, feeding utensils, and cloths used for cleaning them. And when it is claimed that dust or flies play an important rôle in its dissemination, it is not necessary to assume that the bacillus is taken into the mouth or respiratory passages directly, but rather that it is conveyed to water, &c., by means of dust or flies.

Shanghai is situate in the sub-tropical zone and has a climate of wide variation of temperature, but is broadly tropical during the summer quarter and temperate for the rest of the year. Lying on the alluvial flat of the Yangke delta the conditions of soil and sub-soil are uniform in all parts of the Settlement. The ground water-level is about five feet below the surface.