(404) Predisposition. From Dr. Ballard's exhaustive inquiry it seems that contrary to general belief the healthiest children suffer most from diarrhoea; on the other hand, as might be expected, it is most fatal among weakly children. Presuming that diarrhoea is excited by a chemical poison like Vaughan's tyrotoxine, it may be argued that the healthiest children are the greatest feeders, and therefore would be likely to take a greater dose of the poison in milk or other substances; hence this fact may be scored on the side of the chemical theory. (405) Bacteriology of Diarrhoea. Dr. Tomkins of Leicester has investigated the micro-organisms found in the air of diarrhoeal affected localities. Dr. Klein and others have investigated the bacteria found in the intestine and the discharges, but it cannot be said that any very definite result has yet been attained. Tomkins found a larger number of microorganisms in affected areas than elsewhere. For instance, 6,000 colonies of bacteria per cubic metre within the area and 1,600 to 2,300 without the area, but he did not identify the various species nor investigate their pathogenic action. In the discharges Klein found the following: (a) A mobile spore-bearing bacillus which proved to be the bacillus amylobacter. (b) A bacillus resembling bacterium termo. (e) A thin non-mobile bacillus, in some examples containing two or four granules; it grows in clumps and corresponds to the bacillus of Escherlich. (d) Various forms of micrococci differing from one another in size and arrangement; while some formed exquisite chains, others formed more or less sarcina-like groups, while still others were aggregated in clumps or zoogloea. Careful microscopical examination of the tissues and blood of a number of cases of diarrhoea failed to discover any micro-organisms save in one case in which a bacillus was discovered strikingly like that described by Gaffky as the cause of typhoid fever. Dr. Klein is apparently not certain that it is identical; it grew in gelatin more rapidly than Gaffky's bacillus, and had a greater resisting power to mercury perchloride; it was fatal to mice, and the postmortem appearances were those of septicemia. (406) General Results of Dr. Ballard's Inquiry. The general results of Dr. Ballard's inquiry is summed up in the following eighteen paragraphs : A. GENERAL CONDITIONS. 1. Atmospheric Temperature.—That a high atmospheric temperature conduces to a high diarrhoeal mortality, and a low atmospheric temperature to a low diarrhoeal mortality, is an established fact which no one can dispute. But my inquiry shows that the influence thus exerted is not a direct influence, excepting so far as it affects also infant mortality from all causes. It is not the main cause of the diarrheal mortality. Its influence is very great, but is exerted indirectly. 2. Temperature of the Earth.-This is a far more important condition. I have made for London and many other towns in the kingdom a large number of charts, showing week by week for many years the earth temperature at a depth of one foot from the surface, and at a depth of four feet from the surface, each chart showing also the diarrhoeal mortality of the corresponding weeks. The general result shown by these charts is as follows:-(a) The summer rise of diarrhoeal mortality does not commence until the mean temperature recorded by the four-foot earth thermometer has attained somewhere about 56° F., no matter what may have been the temperature previously attained by the atmosphere or recorded by the one-foot earth thermometer. (b) The maximum diarrhoeal mortality of the year is usually observed in the week in which the temperature recorded by the four-foot earth thermometer attains its mean weekly maximum. (c) The decline of the diarrhoeal mortality is in this connection not less instructive, perhaps more so than its rise. It coincides with the decline of the temperature recorded by a fourfoot earth thermometer, which temperature declines much more slowly than the atmospheric temperature, or than that recorded by the one-foot earth thermometer (so that the epidemic mortality may continue, although declining), long after the last-mentioned temperatures have fallen greatly, and may extend some way into the fourth quarter of the year. I do not wish it to be inferred that the atmospheric temperature and the temperature of the more superficial layers of the earth exert no influence on diarrhoea. Their influence, however, is little, if at all, apparent until the temperature recorded by the four-foot earth thermometer has risen as stated as above. Then their influence is apparent, but it is a subsidiary one. 3. Rainfall exerts an Influence on Diarrhea, but (so far as is apparent at present) not equally in all periods of the diarrhoeal season. The diarrhoeal mortality is greater in comparatively dry seasons and less in wet seasons, especially if the drought on the one hand, and rainfall on the other, be remarkably protracted and excessive. But here again the tendency of the inquiry has been to show that the influence exerted is not direct (e.g., by a washing of the atmosphere, so to speak), but indirect, viz., by its effect mainly in preventing the rise and (probably to a less extent) in hastening the fall of the temperature of the earth. 4. Air Movement.-Wind and comparative calm affect the diarrhœal mortality. Other things being equal, calm in the diarrhoeal season promotes it, and high winds tend to lessen it. B.-CONDITIONS OF LOCALITY. 5. Elevation above Sea Level.-This has apparently an influence on diarrhoeal mortality, but not a very remarkable or powerful one. It is an influence which when we regard large areas is lost sight of in the midst of much more powerful influences, and is not perhaps to be distinctly seen until we compare among themselves the different parts of comparatively small areas. In such areas we may often see that the lower levels are more affected than the higher levels; but even here it is not easy to estimate the extent of this influence on account of the disturbance of the result by other more potent influences. But even when most obvious, it has appeared to me that elevation is not an influence that bears specially upon diarrhoea; it affects also, and to much the same extent, mortality from other causes. It seems, in short, to influence diarrhoeal mortality only in so far as it affects infant mortality from all causes together. 6. Soil. I think I am in a position to say that the influence of soil is a decided one; and that although it may be observed in respect to some other causes of mortality (and so is not altogether peculiar to diarrhea), it is observable most distinctly in relation to that disease. (a) Where the dwelling-houses of a place have as their foundation solid rock, with little or no superincumbent loose material, the diarrhoeal mortality is, notwithstanding many other unfavourable conditions and surroundings, low, and may indeed be altogether unnoticeable. Deep and wide and frequent fissuring of a rock in a town, or superficial alternations of rock with looser material, modify this immunity. (b) On the other hand a loose soil, permeable more or less freely by water and by air, is a soil on which diarrhœal mortality is apt to be high. So far as I can see at present, of all natural soils, sand is the most diarrhoeal, other things being equal, unless I class with it surface mould to a considerable depth. Gravel (a very indefinite term, which has a different meaning in different places) varies in its relation to diarrhoeal mortality in proportion as the loose element of it or the stony element and the size of the stones it contains vary. The more gravel approaches sand in its fineness, or to rock in its coarseness, its relation to diarrhoea appears to be greater or to be less. Dwellers on loose slabby rock, as commonly seen overlying solid rock, have more or less diarrhoea in proportion as the slabby material is in small pieces, and mixed with looser earthy matter, or in larger blocks with little intervening earth. Clay soils, other things being equal, do not appear to be in themselves among those soils specially favourable to high diarrhoeal mortality; when they have seemed to be so, the connection has appeared to me to be otherwise explicable. A soil which is a mixture of clay, sand, and stones (commonly called a "marl ") is apparently favourable or unfavourable to diarrhoeal mortality in proportion as it is loose or permeable on the one hand, or plastic on the other. (c) The presence of much organic matter in any soil renders it distinctly more favourable to high diarrhoeal mortality than it otherwise would be. Such organic matter (organic fouling), however, need not be specially of a fæcal or excremental nature to exert this influence, hence diarrhoeal mortality is apt to be high where dwellings are built upon made ground, the refuse of towns, or upon the site of market gardens; or where the earth beneath and about N N dwellings is polluted by neighbouring collections of liquid filth in cesspits, or where sewage has soaked into it from imperfect drains and sewers, or from the surface of the ground. It is the opportunities for the collection of organic filth in the fissures of certain kinds of rock that seem to impart to these rocks, where towns are built upon them, a diarrhoeal character. (d) Moisture or Dryness of a Soil.-Excessive wetness and complete dryness of soil appear to be both unfavourable to diarrhoea. A degree of moisture specially favourable is an amount of habitual dampness which is decided although not sufficient to preclude the free admission of air between the constituent physical elements of the soil. Such a degree of dampness occurs when in the diarrhoeal seasons the sub-soil water stands sufficiently near to the surface to maintain by capillary attraction the dampness brought about by previously greater nearness of the water to the surface; or when the soil, as in the case of marls, contains sufficient of the clayey element to imprison enough of the water saturating it some time previously. It is scarcely necessary to add that the requisite degree of dampness may be produced not only from a source below but from a surface source-for instance, it may be the result of a previous flood or of watery matter habitually soaking in from the surface about houses, or from leakages of such conduits as sewers or drains. 7. Density of Population.-Aggregation favours, dispersion over areas disfavours, diarrhoeal mortality. There is nothing new in this; it is (together with the influence of temperature) the lesson annually repeated to us by the Registrar-General who every year indicates the fact that the diarrhoeal mortality of towns much exceeds that of non-oppidan parts of the country, and that the diarrhoeal mortality of large towns on the whole exceeds that of small towns. The same general lesson is taught by the comparison in particular towns of different parts of the same town, such as I have instituted in the course of this inquiry. But it is to be observed that the influence of aggregation of population is noticed also in respect of infant mortality from other causes: it is not limited to diarrhoeal mortality, although (as shown in the provisional table) it appears most marked in the case of diarrhoea. Moreover, it is to be kept in mind that the parts of towns most densely populated are customarily the parts where the inhabitants are of the lowest |