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.

The efficient control of the spread of yellow fever is a matter of such vast practical importance, both from the hygienic and commercial point of view—not only for the countries where this disease prevails as an epidemic, but also for those in which, after importation, it may assume epidemic proportions—that it has seemed appropriate to bring together in this paper a summary of the work thus far accomplished by the United States Army Commission 1 on the Island of Cuba, during the years 1900 and 1901, in order that English and Colonial readers who have not, perhaps, had access to the original contributions published in different American journals, may be able to form an intelligent opinion concerning the permanent value of this work. It will also afford opportunity for recording the more recent confirmatory observations made by others concerning the mode of transmission of yellow fever discovered by the Commission, and for calling attention to the results already obtained by the U.S. Army Medical Department in the suppression of this disease, especially in the city of Havana, through the enforcement of sanitary measures based on these later researches.

The fact that the blood of ordinary laboratory animals exerts a very marked bactericidal effect upon the Bacillus typhosus and the Spirillum cholerae asiaticae, while it exerts little or no effect upon the Staphylococcus and Streptococcus pyogenes, has hardly received the attention which it would seem to merit in view of the circumstance that these facts involve the important problem as to whether the blood exerts its bactericidal action upon pathogenic organisms generally, or only upon certain species of such micro-organisms.

The time may be considered opportune for bringing forward this subject in that the near approach of the publication of the completely classified results of the census of 1901 will cause the attention of many Medical Officers of Health to be directed to the possibility and desirability of using the census data for working out Life-Tables for their respective districts, and doubtless the construction of many more local Life-Tables will be contemplated than was the case after the census of 1891.

By the existing law for Great Britain it is enacted that “in every room in any factory or workshop sufficient means of ventilation shall be provided, and sufficient ventilation shall be maintained.” Not very much has been hitherto ascertained, however, as to the degree of purity actually existing in the air of factories and workshops generally, or as to what standard of purity may reasonably be expected considering the difficulties met with. A Departmental Committee was recently appointed by the Home Secretary to investigate and report upon the subject. The members of the Committee were Mr E. H. Osborn, Engineering Adviser to the Chief Inspector of Factories, and myself, with Mr C. R. Pendock, one of H. M. Inspectors of Factories, as Secretary. The Committee has just reported on the subject of general ventilation1, but reserving for a future Report the vitiation of air by dust, fumes, &c. from special manufacturing processes.

The numerous additions to the group of Streptothrices which have been recently made, and the close resemblance which the majority of these newly described forms bear to one another, render it by no means an easy task to assure oneself that a freshly isolated member of this group is one that has not previously been met with and described. A curious fact also, which soon strikes anyone who investigates the literature relating to this group of micro-organisms, is that in very few of these has the particular form described by one author been met with by another. While great interest to the bacteriologist naturally attaches to any new species, whatever its source, the group of those which are pathogenic in their action on man, on animals, or on both, are, ipso facto, of more general importance. To this last category belongs the new member of the group which we have isolated from a fatal case of lung disease and pericarditis in man.

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.

That Cattle-Plague (Rinderpest) is one of the most fatal and contagious maladies of cattle needs no further demonstration. The disease appears to be widely distributed in China, and is endemic in the hinterlands of Shanghai, Chinkiang, Hongkong, Pekin, Tientsin, and Chefoo.

The observations here recorded were made, for the most part, during a journey through Upper Palestine and Lower Syria, in June and July, 1901. The country traversed is indicated upon the accompanying map. Its character is so well known as not to need detailed description, being for the most part very hilly and rocky or level plain.

The above experiments show that neither the mineral acids nor permanganate of potash are reliable disinfectants of mud floors against the plague bacillus, even when used in solutions which are many times as strong as are required to destroy the plague bacillus in test-tubes in 15 minutes. This is doubtless owing to the former being neutralized by the alkalies contained in the earth and in the cowdung used for leeping, and to the latter being precipitated and rendered inert by combining with organic matter, which is plentifully present in the leeped mud floors of rooms inhabited by the poorer classes in the large towns and villages of India, which are so often affected by plague.

Of the disinfectants which are sufficiently cheap to be employed on a large scale, there remain phenol and perchloride of mercury in acid solution, the former of which has given satisfactory results on mud floors in a strength of 1 in 50, while the latter is effective in a strength of one part of the mercury salt and two parts of strong hydrochloric acid in 500 of water. If we compare these strengths with those respectively required to destroy plague bacili in 15 minutes in test-tubes, we find that 1 in 750 of phenol and 1 in 20,000 of acid perchloride of mercury solution are effective under the latter circumstances. Thus it appears that in order to be sure of killing micro-organisms of as little resisting power as the plague bacillus on the surface of mud floors, 15 times as strong as solution of phenol and 40 times as strong a one of acid perchloride of mercury as are effective against the plague bacillus in test-tubes in 15 minutes must be used. Thus in proportion to its action on the plague bacillus in test-tubes, phenol is nearly three times as effective on a mud floor as is acid perchloride of mercury. This fact clearly indicates that a portion of the mercury salt is rendered inert by combining with certain constituents of the mud floor, probably albuminous substances, and this may explain the at first sight somewhat surprising failure of a 1 in 1,000 mercurial solution efficiently to disinfect the mud floor. However, when the strength of this solution was doubled, the acid being also doubled, satisfactory results were obtained with the mud floor tested, and the micro-organisms recovered after its use proved to be much highly resistant than the plague bacillus, while they were fewer than even after the use of 1 in 50 phenol. Nevertheless, the neutralizing action of mud floors on the mercury solution will doubtless vary considerably in different places, and it is easy to conceive that in some instances this variable and unrecognisable factor may be considerably greater than in the case of the particular floor used in these experiments, and that even a 1 in 500 solution might be ineffectual under such circumstances. On the other hand, phenol appeares to be free from this objection; and as it gave as good results in a strength of 1 in 50 as the acid perchloride did in one of 1 in 500, it must be considered the safer disinfectant in this strength (1 in 50) in the case of mud floors. In the case of impermeable floors either a 1 in 100 solution of phenol or a 1 in 1,000 one of acid perchloride of mercury is efficient, the latter being somewhat the more powerful of the two, which advantage is probably more than counterbalanced in practice by the disadvantage of using two different disinfectants, if the conclusion that phenol is the better in the case of mud floors is accepted. both 1 in 50 phenol and 1 in 500 acid perchloride of mercury cost about one penny a gallon, the former being very slightly the cheaper of the two in such price-lists as I have been able to consult.

The variable effects of mud floors in partially neutralizing the disinfectant power of perchloride of mercury solutions may possible account for the different estimations of the value of disinfection with this agent in different places and provinces, and also for the failure of the very extensive operations of the year 1900 to prevent the recurrence of plague in the same houses and bustees during the recrudescence of the disease in Calcutta early in 1901. It must also be remembered that the above-noted strengths of disinfectants only act on the superficial layer of floors, etc., and have no influence on the presence of rats, by which, it is now pretty generally admitted, plague is in some indirect way spread—an important factor which must not be lost sight of in estimating the probable advantage of measures of disinfection. Still it is doubtless a good thing to destroy any plague bacilli lurking in a room which has been inhabited by a plague patient, and the practical outcome of the present enquiry is that the perchloride of mercury in hydrochloric acid must be used in at least double the strength that was provisionally recommended by the Plague Commission, and which has up to now, I believe, been very generally relied on in Calcutta. It is still better to substitute a 1 in 50 solution of phenol in every case when mud or earth floors or courtyards form any part of the area to be dealt with, as will be the case in the great majority of instances in which disinfection for plague is required.

The most important of the proteid constituents of milk is casein. From 70 to 90% of the total proteids of milk consists of this substance1. In milk, casein exists as a soluble calcium compound, which is not precipitated by boiling, but from which casein is deposited by the addition of acid or by the action of rennet2. This phenomenon is known as the curdling of milk and is a preliminary to its gastric digestion, both the acid in the stomach and the rennet being capable of producing it. By artificially influencing the nature of its curd we can influence the digestibility of the milk. In human gastric digestion and in the experiments detailed below both acid and rennet are present. The curdling of milk is a necessary preliminary to its digestion in an acid medium, and by influencing this process we can also influence the digestibility of the milk.

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.

Resting Position of the Imago.—Geographical Distribution of the Species.—Habitat.—Modes of Dissemination and Migratory Flights.—hibernation of the Imago.—Longevity.—Oviposition, and the Influence of Food thereon.—Parthenogenesis.—Numerical Proportion of Sexes.—Number of Generations during a season.—Food.—Influence of Heat, Cold, Light, Colour, and Sound.—Sense of Smell and Taste.

Two questions. In concluding our review of this division of the subject, which deals with the parts played by the bodily presence of cellular protoplasm as contrasted with the activity of the chemical products of that protoplasm, which from their solubility may act at a distance from the cell producing them, there are two points which may be alluded to. Firstly, it is difficult to see how, granted that two substances are necessary for bactericidal action, these substances can in the first instance at least meet the bacterium except within a cell. Unless all immune bodies are represented in the serum by go-betweens (Zwischenkörper),—by bodies of an identical nature and differing only in that they are subservient to the normal metabolism of the body—how, when a bacterium gains entrance to the blood, does it come in contact with the immune body for which its protoplasm has the affinity? The receptor, which fixes the group in the bacterium corresponding with it, is within a cell,—how can the affinities be satisfied until the bacterium gets within the cell? It is not till the cell has been robbed of the use of these receptors and they become over-regenerated that the immune body becomes free and can be found in the serum. It is possible that all immune bodies are represented by go-betweens, and that a certain amount of the latter must be kept free in the serum for ordinary metabolism, and it is also possible that when the gradient—to use a physical phrase—between the cell and the blood plasma becomes great so far as the amount of go-betweens present in the latter is concerned that the cell becomes more active and secretes more of the material which is being more rapidly taken up than is usual in ordinary metabolism. Thus while the extra-cellular destruction of bacteria is easy to understand in the later steps of immunisation there is a difficulty about the earlier stages.

The present absence of any Statutory regulations as regards the discharge of sewage and other pollutions into tidal waters has allowed many estuaries in this country to be converted into receptacles for the filth of the sea-port and manufacturing towns situated near the mouth of the larger rivers. Only by an order of the Local Government Board, made after local enquiry and on sanitary grounds, can an estuary be declared a stream and thus brought under the various Rivers Pollutions Acts.

The theories of Ehrlich on the Substances and Mechanisms concerned in the production of Immunity have opened up a very wide field for speculation and research. His view on the formation of the Antitoxins forms the most satisfactory and useful hypothesis which has been produced upon this subject, and is constantly receiving fresh support from the accumulating evidence of numerous observers. But of the more recent developments of his theories as applied to antimicrobic agencies some of the details appear to be at present insufficiently established. With certain of these details it is here proposed to deal.

The outbreak about to be described raises issues of practical importance which appear to make it worthy of record, in spite of the fact that owing to fear of injury to a particular dairyman it was impracticable to complete the evidence by making inquires at every house supplied with milk by him.

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.