Gye and Kettle (1922), from a study of the effects of subcutaneous inoculation of silica alone, tubercle bacilli alone and tubercle bacilli with silica, arrived at the conclusion that there is, after the introduction of tubercle bacilli with silica, “a much greater local reaction than with an infection of tubercle bacilli alone and, further, that general dissemination is earlier and more active.” As a result, “a small dose of bacilli becomes a dose of considerable magnitude and, inasmuch as an important factor in determining an infectious process is the number of organisms introduced, a simple explanation is forthcoming of the effect of silica upon such tuberculous lesions as we have described.”

The results of these investigations on the mineral residues obtained from twenty-nine silicotic lungs, and of the examination of the rocks and materials which gave rise to the inhaled dusts causing these cases of silicosis, lead to the following conclusions:

(1) The bulk of the mineral residues obtained from every silicotic lung investigated by the author consists of minute fibres of the mineral, sericite, a hydrated silicate of aluminium and potassium known also as “secondary white mica.” This mineral is abundantly present also in all the rocks and materials which gave rise to the inhaled dust; and it is present in these rocks and materials in minute fibres and scales of the size it is found in the residues and also in the lung tissue.

(2) Silica in the uncombined state, as quartz, is also present in these residues as relatively coarse and fine grains; it occurs, however, in amounts subordinate to sericite. Especially is this so with regard to the small number of quartz particles, as compared with the countless fibres of sericite.

(3) One relatively large grain of quartz, measuring 10 × 8 × 5 microns such as is found in the residues, is equal in volume to 800 fibres of sericite measuring 2 × 0·5 × 0·5 microns, and contributes as much silica in the chemical analysis of a residue as would 1600 fibres of sericite. This would appear to be out of all proportion to the silicotic effect of one such quartz in the bronchi and bronchioles, compared with the effect in the alveoli of hundreds of fibres of sericite.

(4) Silica in the uncombined state, as quartz, is not the chief cause of silicosis in these and certain other cases. This appears to be conclusively established, it is submitted here, by the following facts: (a) The amount of quartz and the size and form of the quartz grains in the sandstones occurring in the underground working-places in the Scottish Coalfields and in the South Wales Coalfield, are alike. The latter sandstones give rise to dust that has caused scores of cases of silicosis, whereas no authenticated case of silicosis has been produced in the Scottish Coalfields. (b) The gold-bearing quartz conglomerate of South Africa gives rise to dust that has caused thousands of cases of silicosis; the gold-bearing quartz rock of the Kolar Goldfield, India, contains more quartz than the South African rock and yet produces dust that has caused no case of that disease. (c) No quartz-bearing rocks investigated by the author are known to have given rise to silicosis-producing dust except those which also contain abundance of fibrous aggregates of sericite or of fibrous silicate minerals, loosely held together and easily freed into the atmosphere when the rock is drilled and blasted. (d) Rocks which contain a relatively small percentage of quartz (well below the minimum amount in the rock types named in the Silicosis Schemes under English law) but which do contain fibrous silicate minerals such as sericite and sillimanite, as for example at Broken Hill Mines, New South Wales, produce dust that has caused a large number of silicosis cases.

(5) These investigations are not concerned with the pathological condition produced by the minerals in the lungs. Whether they merely act as mechanical irritants causing the growth of fibrous tissue as advocated by some well-known authorities, or induce chemical changes as maintained by certain eminent pathologists, is a question entirely beyond the province of the author. His conclusions do not militate against either theory; on the contrary, they provide the former school with evidence of the presence in the lungs of thousands of acicular fibres that presumably could act as mechanical irritants, and the latter school with evidence of the presence of silicate minerals less stable than quartz and which, because of their physical form, expose far greater surface to volume for any chemical action than do the more compact grains of quartz.

(6) Lastly, it is submitted here that it is mainly the presence in the exploited rocks and materials of fibrous minerals, be they sericite, sillimanite, tremolite, etc. (or a fibrous form of free silica as in chert or of a fibrous rock as in pumice) in aggregates which during the impact of drilling, blasting, or crushing, become freed into the atmosphere as individual fibres, that enables sufficient material in course of time to enter the lungs to cause silicosis. It is not suggested that sufficient minute particles of quartz could not, under any circumstances whatever, enter the lungs to cause silicosis, although the cases here investigated appear to show conclusively that they have not done so; but it is maintained that the fibrous minerals hasten the process so very considerably that their presence in the exploited rocks and materials is of far greater importance in causing this disease than is the presence of quartz.

The factor of the kata-thermometer as deduced from the relation

F = 0·27θ × cooling time in seconds

is not constant, but increases as θ decreases. The relation between F and θ is shown, and it is recommended that the factor should always be corrected to the value corresponding to a temperature of 60° F.

The rate of heat-loss calculated from the factor determined by the still air method is not the true value, but under-estimates it. If the true value is required it can be obtained with reasonable accuracy by increasing the still air value of the factor by 20 per cent, in the case of the body-temperature kata, and 31 per cent, in the case of the high-temperature instrument. For ordinary use however, it is recommended that the still air factor should continue to be used.

Observations were made in still air with standard kata-thermometers and also with silvered instruments. From these observations, and from determinations of the emissivity of the bulbs, the heat loss by radiation was estimated. The remainder after deducting the radiation loss from the total heat loss gave the loss by convection. Estimations of the convection loss from the silvered and plain katas corresponded closely. An equation is given for the convection loss in still air.

The whirling arm method was used for investigating the effects of air velocities up to 1 m. per sec., corrections being made for swirl. The equation deduced from these observations on the standard body-temperature katas was practically identical with the equation of Hill, Vernon and Hargood-Ash. An equation of similar form was found for the silvered body-temperature kata-thermometers, and equations are also given for the high-temperature instruments. When the true rate of heat-loss is used it is found that one equation can be made to fit the observations with both high-temperature and body-temperature instruments, whether the bulb surfaces are of glass or silver.

It is shown that in places where the temperature of the surrounding surfaces differs from the air temperature, a much more reliable estimate of the air velocity can be obtained if a silvered kata is used instead of the plain glass instrument.

A method is given for measuring the emission of radiation from the surroundings by means of ordinary and silvered kata-thermometers, and it is shown that estimates so made correspond, to within 1 per cent., with the values obtained by direct thermopile measurements.

This paper deals with the result obtained after testing, by the “Dick” method, the susceptibility of a series of adults to scarlet fever toxin. The toxin used was produced by the Wellcome Physiological Research Laboratory. While various strengths of solutions were tried to begin with from 1:2500 to 1:250, no advantage was found to result from the use of a solution stronger or weaker than 1:1000. The tests were, therefore, carried out with the standard “Dick” toxin as supplied by this firm.

Tyzzer (1917), who described an epidemic that had appeared in his mouse colony, named the causative organism Bacillus piliformis, giving an inclusive description of its behaviour and morphology. Both natural and experimental infections were studied. The high susceptibility of the Japanese waltzers as contrasted with the relative immunity of the common mice suggests that the disease susceptibility may be linked with the waltzing factor.

Enteric fever in British Guiana, according to official reports, would not appear to be excessively common: the number of notifications for the whole Colony during the years 1930 and 1931 was 244 and 250 respectively on a population of 310,000.

The few observers who have studied this disease in the Colony have all insisted on its sporadic character. Rowland (1910) has clearly illustrated this peculiarity with a series of spot maps showing the distribution of enteric in Georgetown from 1909 to 1913.

In the preceding paper (1933) I have recorded the results of an investigation on typhoid-paratyphoid agglutinins in a random sample of the normal population of British Guiana. It has been shown what a serious cause of error these “natural” agglutinins may represent in the carrying out of routine serological work in certain countries.

The fatty infiltration of the liver which follows the ingestion of medicinal liquid paraffin and many other varieties of mineral oils is more prevalent among females than among males, and is more prevalent among pigmented eye animals than among albino eye animals. When access to the oil lasts for about 30 weeks some 40 per cent, of pigmented eye females and 20 per cent. of the albino eye males may show the condition.

It is the intermediate products, lubricating oils, obtained by distillation of a crude mineral oil which contain the bulk of the constituents which lead to fatty infiltration of the liver, while it is the so-called “spirits” and the residues left in the still which tend to lead to excessive hyaline degeneration of the organs in general. There is evidence to show that fatty infiltration of the liver and hyaline degeneration of the organs are mutually antagonistic, but there is little evidence to show that either condition is directly related to the cancerous process.

The characters by which the “R” variant of a given bacterial type is distinguished from the “S” variant are to-day widely known. Most of them are morphological and in most bacterial types it is not difficult to say whether a single colony is smooth or rough; but every bacteriologist is familiar with those borderline colonies, which are apparently smooth, but which later prove to be serologically rough. It sometimes happens that by special stimulation the reversion from an “R” culture into the “S” form succeeds, but that, notwithstanding the smooth appearance of the isolated colonies, the organisms persist in showing some characters which belong to the “R” variant, such as instability in saline (Bruce White, 1926).

1. An agar medium is described which enables a direct estimation of the numbers of coliform bacilli in a water or milk sample to be made.

2. An enrichment medium for B. lactis aerogenes is one containing in every 100 c.c. of peptone water 0·5 g. sodium citrate, 0·25 g. soluble starch and 1 c.c. of a 1 per cent, watery solution of neutral red.

3. Enrichment media for B. coli are: (a) lactose peptone water containing in every 100 c.c., 1 g. sodium sulphite anhydrous and 2 c.c. of 1 per cent, rosolic acid in absolute alcohol; (b) lactose peptone water containing in every 100 c.c., 2 c.c. of a 40 per cent, solution of hexamine in water.

4. Importance is attached to the capacity to ferment starch possessed by B. lactis aerogenes.

5. The application of these media to the examination of water and milk is indicated.

Hecht (1923) states that the haemolytic activity of serum complement disappears on standing, but that the activity can be restored by the addition of heated fresh serum. It has also been shown (Gordon and Wormall, 1928; Gordon, 1930;. Gordon and Carter, 1932) that the bactericidal action of serum involves the activity of a complement similar to haemolytic complement and that inactivation of the latter by dilute ammonia and congo red causes, at the same time, inactivation of the bactericidal complement. The experiments now to be described show that the similarity of the two complements is exhibited once again in the effect of long standing on serum.

In 1890 Klein described two types of colony of the diphtheria bacillus on gelatin; one smooth and circular, the other radiating and resembling a daisy. Cowan (1927) observed two types of colony, but one of the types was thought to be due to roughening. Parker (1928) observed three types of colony, some of which were considered ordinary rough variants.

1. The annual number of notified cases of erysipelas is approximately 17,000, and assuming complete notification of the disease the general case fatality is approximately 6 per cent.

2. The death-rate, deaths in terms of the population, varies according to age, being highest at the beginning and end of life and at a minimum between the age of 5 and 10 years. The mortality of males is identical with that of females up to age 25, but is afterwards in excess.

3. The disease has in recent years a well-marked seasonal incidence—a winter and spring excess with a summer defect. In this respect it resembles scarlet and puerperal fevers and, although its seasonal incidence has changed in the course of time, the alteration has not been nearly so pronounced as that for scarlet fever.

4. The incidence is highly correlated with overcrowded conditions, the correlation coefficient being in some periods as high as + 0·83 in the divisions of London and + 0·70 in the sanitary districts of Glasgow.

5. The morbidity from erysipelas is fairly well correlated in time with that from scarlet fever and erysipelas, but in London, in the urban and in the rural districts of England and Wales, the spacial correlation is very small. On the other hand, in Glasgow the spacial correlation between the incidence of erysipelas and that of scarlet fever is highly negative, −0·718 ±0·109, whereas between erysipelas and puerperal fever the association is positive, + 0·689±0·109 during the period 1903–8, but these values were much reduced when the partial coefficients were calculated.