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The disposal of wastes from paper and pulp mills—a problem of particular importance in the northern European countries of Norway, Sweden and Denmark, where wood-processing is one of the main industries—is discussed. The various types of waste produced are described, and their pollution potential is assessed, in terms of population equivalents, with special reference to the present position in Finland. The methods available for the treatment of these wastes are briefly outlined.

This paper reports the gross and rapid condensation of isoniazid in a commercial black-currant-flavoured syrup. In vitro studies showed that the condensation was due, at least partly, to the glucose contained in the syrup, paper chromatography having demonstrated the presence of D(+)-glucose isonicotinoyl hydrazone. Controlled studies in human beings showed that the absorption of isoniazid from the preparation was considerably impaired by this condensation.It is concluded that sugars such as glucose, fructose, and sucrose-especially glucose-should not be used in isoniazid syrup preparations, and it is suggested that sorbitol, a stable non-carbonyl compound, might be a suitable substitute.

Two approaches to the attenuation of influenza A2 virus were studied: adaptation to a sub-optimum growth temperature and the production of temperature-sensitive mutants.A strain of A2/Hong Kong/68 virus was adapted to growth at 25 degrees C in calf kidney tissue culture, and a virus suspension was prepared for administration to volunteers after cloning by 2 terminal dilution purifications. The results indicated that the low-temperature-adapted strain had reduced infectivity for man, but was not attenuated since illness occurred when sufficient virus was administered to infect all volunteers.More encouraging results were obtained with 2 temperature-sensitive mutants of influenza A2/1965 virus. One of these mutants was unable to form plaques in calf kidney tissue culture at temperatures above 36 degrees C; the other showed restriction of plaque formation only at 38 degrees C and above. Both mutants were able to infect hamsters, but compared with the wild-type virus there was marked restriction of replication in the lungs. Prior infection of hamsters or mice with either mutant induced significant resistance to subsequent challenge with wild-type influenza A2 virus.

The double-stranded complex of polyriboinosinic acid and polyribocytidilic acid (poly I·poly C) was shown to inhibit effectively the infection of human cells with 4 common human respiratory pathogens—influenza A2, rhinovirus 13, respiratory syncytial and parainfluenza-1 viruses. This protection was observed with levels of poly I·poly C which did not induce the release of detectable amounts of interferon. Mice could be protected from pulmonary influenza A2 infections by intranasal instillation of poly I·poly C before challenge with virus. Administration of poly I·poly C directly to the respiratory tract was found superior to systemic administration in the case of the pulmonary infection studied.

As a basis for a series of studies on the pharmacological, therapeutic, and addictive properties of synthetic drugs with morphine-like effect, this paper deals with chemical aspects of the compounds of this type so far known. Four major groups, each with a fundamentally different chemical structure, are described: pethidine, methadone, morphinan, and dithienylbutenylamine. For each substance belonging to these groups, the formula, synonyms, and methods of synthesis are indicated. A description of pethidine according to the specifications of the Pharmacopoea Internationalis is annexed to the paper.

In a paper arising out of an informal international consultation of specialists in the bacteriology of tuberculosis held in 1961, an attempt was made to formulate criteria, and specify technical procedures, for reliable tests of sensitivity (the absolute-concentration method, the resistance-ratio method and the proportion method) to the 3 main antituberculosis drugs (isoniazid, streptomycin and p-aminosalicylic acid). Seven years later, a further consultation was held to review the latest developments in the field and to suggest how sensitivity tests might be put to practical use in tuberculosis control programmes. The participants reached agreement on how to define drug sensitivity and resistance, and stressed the importance of using a discrimination approach to the calibration of sensitivity tests. Their views are contained in the present paper, which also includes descriptions of the sensitivity tests used by the Medical Research Council of Great Britain for first- and second-line drugs (minimal inhibitory concentration and resistance-ratio methods), the two main variants of the proportion method developed by the Institut Pasteur, Paris, and a method for calibrating sensitivity tests.

In the first country-wide survey of hookworm infection in Liberia, diagnosis by test-tube filter-paper cultivation revealed a prevalence of more than 90%. This sensitive technique also permitted differential species determination. Necator americanus was found to occur in all regions and in a high proportion of the persons examined. Ancylostoma duodenale was mainly confined to a narrow coastal belt, and usually parasitized individuals harbouring N. americanus as well. The average number of eggs per gram of faeces (EPG) of infected individuals was lowest in the population of the hinterland. During the latter part of the studies a modified test-tube filter-paper cultivation technique was used in combination with dilution counting to obtain data on intensity of infection separately for the 2 species. For N. americanus there was little regional difference in the intensity of infection, but the EPG for A. duodenale was much higher in people living in the coastal area.

Because of the inaccuracy inherent in mass chest radiography it would be desirable to have the chest films examined by the most efficient interpreters and to apply the film material that permits the most efficient interpretation. But before this can be achieved a method for an objective evaluation of efficiency must be developed.In the present paper a method is suggested for evaluating the efficiency of one important activity in film interpretation-namely, the determination of whether or not there is an abnormal opacity in a chest X-ray film. A test procedure is described that may be used for collecting the required data in respect of different interpreters and different types of film material. A discussion of the test data is presented and a method of analysis suggested. It is hoped that the general considerations concerning diagnostic efficiency given in this paper may be useful in the development of methods for evaluating other diagnostic procedures.

In 1953, the Department of Biological Standards, National Institute for Medical Research, London, was authorized by the WHO Expert Committee on Biological Standardization to proceed with the establishment of an International Standard for Thyrotrophin. A number of laboratories were requested to assist in the collaborative study of the proposed new standard, and those which agreed were sent a short note (annexed to the paper) explaining the basis of the study. In this paper, the authors describe the assay methods used by ten laboratories and discuss the results obtained.

This paper discusses the evidence for and against the view that the spectrum of pathological changes in leprosy, extending from the lepromatous form to the tuberculoid form, may be caused by differences in the immune responses of patients. Patients with the tuberculoid form of leprosy generally have well-developed specific cell-mediated immunity, but in a large proportion of patients with lepromatous leprosy the specific cell-mediated immunity to Mycobacterium leprae and sometimes to other antigens seems to be deficient, whereas the circulating antibody response is well-developed. Techniques for assessing the immune response in patients are described in detail with the objective of improving the comparability of such investigations. The paper also discusses the importance of several investigatory approaches to clinical leprosy and the value of animal models for leprosy research.

This paper presents a comparative survey of the methods and apparatus used in Italy, particularly in Genoa, for measuring the three main components of city air pollution-sulfur dioxide, dustfall and suspended matter.The most frequently employed devices for sampling sulfur dioxide are the lead-peroxide and volumetric apparatuses, as developed by the British Department of Scientific and Industrial Research. For the collection of dustfall, the British standard deposit gauge is widely used; in Genoa, a simple, low-cost type of dustfall collector has been tried in combination with that gauge, and good results have been obtained. The measurement of suspended matter is effected by the thermal precipitator, electrostatic precipitator and konimeters of different types, in addition to the classic method of filtration through various media. In Genoa, suspended matter is monitored by automatic filter-paper samplers and directional samplers. The use of membrane filters for counting dust particles has proved particularly satisfactory.All these techniques are described in detail, and their results are subjected to statistical analysis.

This paper presents the results of the tuberculin-testing of over 3,600 patients in tuberculosis hospitals and of nearly 34,000 schoolchildren in widely separated areas where arrangements could be made for specially trained personnel to work with uniform materials and techniques. Both patients and children were tested with an intradermal dose of 5 TU, and the children were retested with 100 TU if the reactions were less than 5 mm.THE RESULTS CONFIRM THOSE OF EARLIER PAPERS, THAT AT LEAST TWO DIFFERENT KINDS OF NATURALLY ACQUIRED TUBERCULIN SENSITIVITY ARE FOUND IN MANY HUMAN POPULATIONS: a high-grade sensitivity, designated as specific for virulent tuberculous infection, and a low-grade kind designated as non-specific, or not specific for tuberculous infection. Specific sensitivity is the kind found in tuberculous patients and in some schoolchildren everywhere. It follows a remarkably uniform pattern wherever it is found, apparently varying only in prevalence, not in degree, from place to place. In contrast, non-specific sensitivity varies both in prevalence and in degree. It ranges from nearly universal prevalence in some localities to almost complete absence in others, from a low degree to a relatively high degree approaching that of specific sensitivity. Non-specific sensitivity is not correlated with specific sensitivity and may have different causes in different places.Serious practical problems are encountered as the prevalence and intensity of non-specific sensitivity increase, because the larger non-specific reactions cannot be distinguished from the smaller specific reactions with the tuberculin products in use today. A better, though not entirely satisfactory, separation of infected and uninfected persons might be obtained by using different criteria in different geographic areas for what is called a positive reaction to the 5 TU test. Changing the current criterion would probably provide a better estimate of the prevalence of infection in some communities: a lower proportion of the uninfected would be called positive at the expense of calling a few infected persons negative.The analogous problem of separating specific from non-specific sensitivity in cattle has been provisionally solved by the veterinarians by comparative testing with tuberculins made from different types of mycobacteria. Similar methods are now being investigated for possible application to tuberculosis control work in human populations.

The interpretation of surveys of DDT-resistance in body-lice is handicapped by the fact that the genetics of this form of resistance have not been studied. This paper reports on a preliminary investigation on normal and resistant strains of lice, F(1) and F(2) hybrids of a mass cross and F(1) x R hybrids exposed to DDT dust and DDT-impregnated paper of various concentrations. The results were consistent with inheritance by a single gene pair (or possibly a small number of genes). The F(1) hybrids were intermediate in tolerance but were all killed by 5% DDT dust. This confirms a suggestion that 5% DDT dust would be suitable for testing for incipient resistance.

So many developments have taken place in the field of nuclear energy since 1956, when the author's previous paper on radioactive waste disposal was published in the Bulletin of the World Health Organization, that a fresh review of the subject is now appropriate.The present paper deals with those aspects of the problem which are of most interest to the sanitary engineer. It considers specific points in the latest recommendations of the International Commission on Radiological Protection in relation to public drinking-water supplies, and examines the problem of fall-out, with special reference to the presence and significance of strontium-90 in drinking-water. A general survey of the various uses of radioactive materials is followed by a discussion of the legislative and control measures necessary to ensure safe disposal of wastes. The methods of waste disposal adopted in a number of nuclear energy establishments are described in detail. The paper concludes with some remarks on solid waste disposal, siting of nuclear energy industries and area monitoring.

Although the fluorescent antibody (FA) test for human bilharziasis described by Sadun and colleagues has proved of great value, its use involves certain difficulties which the author of the present paper has attempted to obviate. The first part of the paper describes a cheap and reproducible method for producing a cercarial antigen conjugated with rhodamine B 200 for use in the indirect FA test. The second part deals with a new modification in which the conjugated cercarial antigen is employed with a bentonite-absorbed FITC antihuman globulin serum and discusses the advantages of this test over the normal FA test.Experience has shown that the use of rhodamine-albumin-coated cercariae, conjugated cercariae or normal fixed cercariae as antigens does not always give valid results when compared with those obtained with the FA test or the ordinary complement-fixation test in bilharziasis. In the third part of this paper, however, the author describes a modification of the complement-fixation test involving the use of a bentonite-absorbed fluorescent antiguinea-pig serum and the RB 200 conjugated cercariae described earlier. This test has given reproducible results in known positive control human sera which have been valid when compared with the Sadun FA test, the conjugated cercarial FA test and the bentonite fluorescent antibody test described in the second part of this paper. In some instances the test results have also been supported by evidence from standard skin tests.

This paper considers the participation of macrophages, thymus-dependent lymphocytes (T-cells), and thymus-independent lymphocytes (B-cells) in man's immune response to malaria. Although phagocytosis by macrophages is an important feature of malaria the full extent of cooperation between these cells and T- and B-cells is not known. Evidence that T-cells play an important defensive role is at present unconvincing. B-cells on the other hand function importantly in the synthesis of immunoglobulins and specific antibodies and factors possibly influencing their activity are considered. Different epidemiological patterns of malaria antibodies in sera are described and the need for the routine inclusion of reliable antibody detection tests as part of malaria survey techniques, particularly where antimalarial drug usage is frequent, is emphasized.

A new fluorometric method for analysis of amodiaquine in serum, plasma, or red cells is described. Amodiaquine is extracted from alkalinized biological fluid into 1,2-dichloroethane and is then re-extracted into 0.1 N hydrochloric acid. Borate buffer is added to the acid solution and the resultant solution is heated for 30 min in boiling water. Heating the buffered solution produces a marked increase in the fluorescence of amodiaquine, which may then be measured. Standard curves prepared in serum and red cells were linear between 50 and 3 000 mug/litre. Reproducibility of the assay and recovery of amodiaquine from serum and red cells were satisfactory. The specificity of the assay and the nature of the induced fluorophor are not known. The paper indicates representative serum and red cell levels of amodiaquine after the administration to 5 subjects of 10 mg of amodiaquine base per kg of body weight.

Previous reports from India have been limited to the incidences of hepatitis B antigen (HB Ag) in health and disease. This paper reports on a study undertaken over the last two years to determine the incidence of hepatitis B virus infection, the serotypes prevalent among apparently healthy individuals and patients with liver diseases, and the seasonal incidence of sporadic acute hepatitis in this geographic area. The incidences of infection in health and disease show an endemic pattern. The Y subtype predominates among healthy carriers and patients with chronic liver diseases, whereas the D subtype predominates in patients with acute hepatitis. The similarity of subtypes of HB Ag among the majority of healthy carriers and patients with chronic liver diseases suggests that the majority of asymptomatic carriers (subclinically infected) would develop chronic liver disease. The proportion of HB Ag-positive cases of acute hepatitis was significantly higher during the two summer seasons than during the two winter seasons; this could be due to more frequent transmission of the virus by the faecal/urinary—oral route and its activation during the summer months, especially in areas with poor hygienic conditions. The urinary/faecal excretion of virus could thus maintain the natural transmission of the virus in such an environment.

This paper reviews and discusses a technique that can be used to study the dynamics of populations under the influence of favourable or unfavourable environmental factors or the stress of population control. It is encouraging for those interested in the sterility approach to pest control that the reproductive success of insects with a reputedly high biotic potential is limited to relatively low rates under field conditions. Further studies are needed under other conditions, in other areas, and with other species.

In an extension of recent work on the antigenic interrelationships of arthropod-borne viruses, the plaque-inhibition test has been applied to the study of 15 Group A strains. Middelburg and eastern equine encephalomyelitis viruses show no relationship to any other virus in the group. Sindbis and western equine encephalomyelitis viruses show a one-way relationship only. The remaining viruses all share some antigenic components which react with hyperimmune rabbit sera prepared against Semliki Forest virus. However, using single-dose rabbit sera, or more specific mouse-immune sera, four distinct subgroups can be defined. One includes Semliki Forest virus strains; another Chikungunya virus and its substrains, Vereeniging and TH 35 viruses; the third contains O'nyong-nyong virus; and the fourth Mayaro and Uruma viruses.This paper also demonstrates how the plaque-inhibition technique may be used for the rapid identification of new virus isolates.

Previous reports from the Tuberculosis Chemotherapy Centre, Madras, have established that ambulatory treatment of pulmonary tuberculosis with the combination of isoniazid and PAS, administered daily, yields satisfactory results. However, in the usage of any unsupervised regimen, reliance must be placed on the co-operation of patients in self-administering their drugs. Irregularities in drug-taking, which are not uncommon, may lead to unfavourable therapeutic results; this might be avoided by supervised administration of the drugs. Daily supervision is clearly impracticable in developing countries but regimens in which the drug is administered intermittently-say, twice a week or less frequently-are, if effective, more likely to gain general application.This paper presents the results of a controlled study of a fully supervised intermittent regimen of isoniazid (12.5-16.1 mg/kg body-weight, orally) plus streptomycin (injected in a uniform dose of 1 g), given together twice weekly, compared with a standard, unsupervised, daily, oral regimen of isoniazid (3.7-6.3 mg/kg body-weight) plus sodium PAS (0.2-0.3 g/kg body-weight), given in two doses. The intermittent regimen was at least as effective as the standard oral regimen, and although the incidence of temporary giddiness in patients receiving this regimen was rather high, this did not appear to have any long-term importance nor did it appear unduly to affect the co-operation of the patients. These encouraging findings suggest a possible change in the orientation of drug-administration for tuberculosis in developing countries.

The biological control of insects carrying human diseases was first attempted many years ago, but the results were disappointing owing to the insufficiency of information on the ecology and pathology of such insects at the time. In recent years, however, increased knowledge of insect pathology and ecology and the development of insecticide-resistance have led to a revival of interest in this method of vector control. Most of the recent published work on this subject relates to findings in North America; comparatively little information has hitherto been available in respect of Europe. This paper, which is based on a survey of the literature and on the author's own experience, presents the results of research on diseases of insects of medical importance in Europe. Infection with viruses, rickettsiae, bacteria, fungi, protozoa and nematodes are discussed and suggested lines for future European research on biological control are put forward.

There is not a single pesticide for which the interrelationships between occupational exposure by different routes, the fate of the compound in the human body, and its clinical effects are all adequately known.Results of the direct measurement of exposure to pesticides may be used in evaluating the relative hazard of different routes of exposure, different operational procedures, and different protective devices. Results of the indirect measurement of exposure may be of use for the same purpose; in addition, these indirect measures may be used in relating exposures under observed conditions to clinical effects.This paper describes and evaluates detailed procedures for the use of air samples, pads, and washes in the direct measurement of the dermal and respiratory exposure of workers to pesticides. Good methods are not available for measuring oral exposure. Any measure of the absorption, storage, physiological effect, or excretion of a compound constitutes an indirect indication of exposure to it.

In the laboratory assay of typhoid vaccines many questions still remain open. The results of experiments are at times ambiguous, and there is no satisfactory agreement between them and the results of the various field trials. The authors of the present paper have attempted to clear up some of the causes of discrepancy. They have concluded that in evaluating the efficacy of various types of vaccine much depends on the vaccine and challenge doses used. By employing low or high doses of vaccine, it is possible to obtain different results in respect of the qualities of the vaccines compared. The time interval between vaccination and challenge also has a certain influence.Experimentally infected mice were examined for the presence of Salmonella typhosa in the peritoneum and in the blood. The authors' experiments show that bacteraemia, observable 30 minutes after intraperitoneal challenge, represents an important indicator of vaccine efficacy. This approach enabled them to obtain clearer and more detailed information regarding the protective power of the vaccine employed than would have been revealed by the more death or survival of the test animals.

This paper is based on an analysis of questionnaires sent to the health ministries of Member States of WHO asking for information about the extent, nature, and scope of morbidity statistical information. It is clear that most countries collect some statistics of morbidity and many countries collect extensive data. However, few countries relate their collection to the needs of health administrators for information, and many countries collect statistics principally for publication in annual volumes which may appear anything up to 3 years after the year to which they refer. The desiderata of morbidity statistics may be summarized as reliability, representativeness, and relevance to current health problems.

The practice of waste water utilization has grown considerably in recent years, owing to the growing demand for water for agricultural, industrial and domestic purposes. Such utilization presents certain problems in respect of the quality of the reclaimed water, on account of the presence of certain trace chemicals in the waste waters to be re-used. The presence of these trace chemicals may have important consequences in the agricultural or industrial utilization of waste waters, but from the public health point of view it is in the re-use of waste waters for domestic purposes that their presence has most importance, owing to their possible toxic effects.This paper discusses the public health significance of trace chemicals in water, with special reference to some of the newer complex synthetic organic compounds that are appearing in ever-increasing numbers in industrial wastes. Current information on the acute and chronic toxicity of these substances is reviewed and related to possible methods of treatment of waste waters.In conclusion, the author points out that the problem of trace chemicals is not confined only to direct waste-water reclamation projects, but arises in all cases where surface waters polluted with industrial wastes are used as a source of domestic supply.

In the course of a village-scale trial of fenthion, carried out in a village near Lagos, Nigeria, 40% fenthion water-dispersible powder was used at a 3.75% concentration. This was applied by Galeazzi "OM" sprayers with constant-pressure assemblies. The target concentration was 1.5 g/m(2). Filter-papers were placed on walls, ceilings and roof beams to determine the actual average rate of application, and glass plates were placed on the floors to determine the rate of "bounce-off" from the walls or of "drop-out" from the ceilings. The results of chemical tests show that the rate actually applied came closest to the target concentration on the walls, followed, in that order, by ceilings and roof beams. There were heavy deposits on the floors up to 30 cm away from the walls. The authors analyse the causes for the variations encountered.

Fava beans (Vicia fava) are cultivated rather widely in most countries of the Eastern Mediterranean area and provide a cheap but protein-rich food that can be eaten alone, in various culinary preparations, including bread, or as a dietary supplement. However, the ingestion of fava beans may induce a haemolytic disease—favism—in some susceptible individuals and this might appear to limit the use of this pulse crop in those regions where favism occurs frequently. The uses of fava beans in Iran, the characteristics of favism and the present state of knowledge of the pathology of the disease are reviewed in this paper. Although some progress has been made in identifying the toxic substances and in explaining their mode of action, our understanding of favism is still limited. It appears that the disease is seen particularly in young children and is associated with a deficiency of glucose-6-phosphate dehydrogenase (G6PD) in the blood.

Many developed countries are faced with the problem of reorganizing their tuberculosis-control programme to bring it into line with modern conditions. The study reported was undertaken to provide guidelines for this reorganization. It was begun in the district of Kolín, Czechoslovakia, with a population of some 100 000, in 1961 and is still in progress. The paper covers the first 4 years of the study.In 1961 a thorough check-up was made on all persons registered as having active or inactive tuberculosis, or fibrotic lung lesions. In 1961 and 1963 a mass X-ray and tuberculin-testing campaign, with 95% coverage, was carried out for all persons over 14 years of age. All persons with active tuberculosis received adequate treatment. Persons registered as having tuberculosis or suspected tuberculosis were subjected to regular photofluorographic and bacteriological investigations. Newborn infants were given BCG vaccination, and persons aged 14 years and 19 years with negative tuberculin reactions were vaccinated.The prevalence of bacillary tuberculosis fell from 150 cases in 1960 to 91 in 1964, mainly owing to a decrease in the number of chronic cases. The incidence of bacillary tuberculosis detectable by direct smear microscopy, however, remained at about 25 cases throughout the period 1961-64. The risk of developing tuberculosis was found to be highest in persons with fibrotic lung lesions or inactive tuberculosis, and in men above 45 years of age and women above 65 with previously normal photofluorograms.It is concluded from the study that in developed countries priority should be given to adequate treatment of all persons with active tuberculosis, and to early diagnosis in persons consulting physicians and in the high-risk population groups.

Tests to determine mycobacterial sensitivity to antituberculosis drugs have become a routine procedure to enable clinicians to apply the most suitable treatment. However, while antimycobacterial drugs have been widely and successfully used in recent years, laboratory techniques for performing drug sensitivity tests have not yet been standardized and thus do not permit international comparison of results.Among the main hindrances to standardization are differences in the sensitivity of culture media, the capacity of some of the ingredients to adsorb certain drugs, the decomposition of some drugs when exposed to high temperatures during coagulation of solid media, and difficulties in the preparation of standard inocula.The techniques described in this paper have been used with success to determine the sensitivity to the three major antituberculosis drugs (isoniazid, streptomycin and p-aminosalicylic acid) of 600 strains of mycobacteria isolated from 200 newly diagnosed cases in a WHO-sponsored field trial. In all these patients, sputum conversion was achieved by treatment with a combination of the three drugs, without the emergence of resistant strains.The cytochemical tests recommended by the authors for routine use in the differentiation of mycobacteria are a combined test for catalase and peroxidase activity and either the niacin test or, preferably, the Virtanen-Griess nitrate test for differentiating Mycobacterium tuberculosis from Myco. bovis.

The development of resistance by a single vector population to the two main insecticides (DDT and dieldrin) used in malaria eradication programmes is as yet a comparatively rare event, but one of a potentially serious nature when it does occur.This paper describes the background of one such instance-double resistance by Anopheles aconitus in Java-and gives the results of observations made on this mosquito population, including its reaction to sprayed structures.Judged on the basis of the mortality produced and of the reduction in biting in sprayed structures, DDT was found to have little effect on A. aconitus. Malathion, on the other hand, gave fairly satisfactory results under the conditions prevailing in the experimental area.

Testing urine specimens obtained at surprise visits to the home or at routine clinic attendance is an established procedure in the supervision of patients receiving ambulatory chemotherapy for pulmonary tuberculosis. A urine test service was set up in 9 East African centres, involving 37 staff members (most with limited training) who conducted a simple paper test for isoniazid. Analysis of the results obtained yielded an unbelievably high proportion of positive results, indicating that the testing system, as organized, had been a failure. Special investigations were therefore carried out into the reasons for this.Over-reading of test results, incorrect performance of the test, and, in 1 centre, dishonest recording were found as explanations. Discussing the implications of their findings, the authors stress the importance of close supervision at all stages of tuberculosis-control procedures in the field, no matter how simple; and they point out with reference to urine testing that, even if a centralized testing system, involving a sensitive test method and quality control, were to be set up in regional laboratories, adequate supervision at all stages would be essential.

Identification of the larval stages of African Simulium—vectors of onchocerciasis—is becoming increasingly important. In this paper attention is drawn to the principal morphological structures that are of value for identification and illustrations are given to indicate the various characters mentioned. The author provides an identification key to the larvae of the different species-groups of African Simulium and to the larvae of those species of most importance to man, and also presents a tentative key by which a larva may be placed in the probable instar of its development.

In experimental work with tuberculin testing-for example, for comparing different testing procedures, for standardizing tuberculin, etc.-two tests are often given to each person. Because of variations in allergy from person to person, such duplicate testing gives a much more precise comparison of two test procedures for a given number of persons than does the alternate use from person to person of two test procedures to be compared. In adopting this method of testing it is tacitly assumed that the two tests in the same person do not interact in any way. The present paper shows, however, that this assumption is not justifiable.The authors describe an experiment in which 611 infants who had been BCG-vaccinated at 2-5 days of age were tuberculin-tested 3-5 months later, 306 of them with a single 10 TU test and 305 with a 10 TU test in one arm and a 100 TU test in the other arm. The results showed that there was a highly significant difference between the two groups, both in the average size of the reactions and in the degree of induration, the single-test group giving the larger and stronger 10 TU reactions.

By immersing groups of rodents into several types of natural waters at Malelane, Eastern Transvaal, and subsequently recovering schistosomes from them, the authors have shown that there is seasonal transmission, which is more marked with Schistosoma mansoni than with S. mattheei. Laboratory confirmation of this periodicity was obtained by infecting groups of snails with the appropriate parasite and studying the pattern of sporocyst development and cercarial shedding under outdoor conditions. It was also found that, apart from seasonal periodicity, the amount of transmission is dependent on the density of human population, the proximity of the definitive host to the immersion site, the degree to which the water is protected from pollution and the distance downstream from the polluting source.Negligible numbers of S. haematobium adults were recovered; possible reasons for this are discussed.The authors consider that an annual transmission cycle may be more common in bilharziasis than is generally supposed-although not exclusively or necessarily for the reasons given in this paper-and suggest that such a cycle be taken into consideration in the planning of control schemes.

A previous report from the Tuberculosis Chemotherapy Centre, Madras, has shown that, if standard chemotherapy is given for one year, the response of patients treated at home in very poor environmental circumstances is nearly as good as that of those treated in sanatorium under much more favourable conditions. This paper reports on a four-year follow-up of all the patients whose disease was bacteriologically quiescent at the end of the year's treatment. During this period, all the patients were managed on a domiciliary basis; about a quarter of them received chemotherapy with isoniazid alone for two years, another quarter received the drug for one year and the rest received no specific chemotherapy. Despite adverse environmental factors (poor diet; long hours of work often involving strenuous physical activity; overcrowded living conditions; and, for the sanatorium patients, the stresses of returning suddenly to the unfavourable home environment), the great majority of patients in both series maintained quiescent disease throughout the follow-up period. Furthermore, the few patients whose disease relapsed bacteriologically were at no special dietary disadvantage in comparison with those who maintained quiescent disease throughout, nor did they show any appreciable differences in occupation, physical activity or living accommodation. These findings, together with the earlier ones, indicate that, despite adverse environmental circumstances, standard chemotherapy for an adequate period of time is sufficient in the great majority of patients for the attainment of bacteriological quiescence and its maintenance thereafter.