the phial under the hooded pipette, forces into it the proper amount of serum, and hands it to the Director. He in turn has already taken up a sterilised cork with a sterilised forceps; instantly he fits the cork into the phial over the flame, and hands the corked phial to the Laboratory Boy. He in his turn dips the corked end into the boiling paraffin and sets the phial down. These operations are carried out so rapidly that some 600 phials may be filled in an hour. After the bottling the phials are kept in an incubator for twenty-four hours, and, if possible, longer. If at the end of that time any one of a set shows the slightest sign of impurity or microbic life, the whole set is destroyed. Such is the care taken in the preparation of these delicate antidotes to those delicate and remorseless poisons. What the resut of this day's bottling may be we shall doubtless hear in due

season.

Afterwards I was taken round the farm, which has twenty-two horses, many rabbits, and guinea-pigs by the score. Among the horses the Director pointed out the first pony that had ever yielded anti-diphtheretic serum in Britain. He had now ceased to yield any; but he was kept as an interesting old friend, and he was quietly enjoying the life he had so well earned by his blood. The other interesting phenomena of this marvellous factory of animal fluids it would lead me too far from my purpose to describe.

What I have described, however, is intended to bring out a sharp contrast. At this farm we find that diphtheria has a perfectly definite meaning; it yields its poison; it produces its definite sequences of morbid phenomena; it produces its antidote. At every stage it is under control; its actions and reactions can be predicted; its precise strength can be measured; it can be neutralized to a perfect nicety. I was shown about a pint and a half of diphtheria fluid which, so I was informed, was the most concentrated and strongest diphtheria poison hitherto produced in the world. Yet it was in use there to produce definite, predictable results. This is on the one hand: a definite set of logical relations, a definite theory of causation, a definite verification in practice.

What is there on the other hand? There are masses of speculations and observations and statistics; cases and epidemics and deaths; contention and argument and counter-argument. There are disputes on the part that is due to air, to climate, to season, to situation, to soil, to subsoil, to water, to soil-water, to dampness of houses, to absence of light, to filth, to accumulations of refuge, to decaying vegetables, to unsanitary drains, to articles.

of food, to the lower animals, to personal disposition, to personal habit, to personal contagion, to the aggregation of children in schools, and to many other more individualized and detailed circumstances and conditions. Here, therefore, there is room for much scientific labor; innumerable disputes are impossible; but it ought to be the endeavor of the men of practice to bring to these vast masses of unorganized observation the same definite and persistent methods as characterize the men of science, who are, after all, the most highly developed men of practice.

In a paper read before this Association last year I gave a brief and general outline of diphtheria as it is at present known to science. This year I have been requested to open a discussion on the causation of diphtheria. Logically, cause is the particular combination of conditions that precedes any occurence of the disease. When diphtheria is pure, as in the laboratory, it is a name for the life-history of the Klebs-Loffler bacillus growing in a certain media-whether the medium be an albuminous fluid. in a test-tube or the varied tissues of an animal. For a pure case of the disease, therefore, the question of causation may be regarded as no longer open. When, however, diphtheria is impure or mixed, as it almost invariably is in the actual human being, the question of cause is no longer so simple. It then becomes necessary to determine-not whether the bacillus working in a particular medium will cause the disease, but--why the disease has occurred in a particular place at a particular time. And this is a vastly more complex question. The media for the growth of the bacillus are no longer limited to the known compositions of the bacteriological laboratory; they are various as the conditions of life in a complex civilization. Here, therefore, it is possible to indicate only a few of the conditions that may become the cause of an actual case at a particular time in a particular place. As far as possible I shall try to indicate those conditions through an actual instance. Doubtless the experience of most at this Congress will furnish other instances equally relevant.

1. Climate. By climate I mean the prevailing weather of a locality. In the 1892 report by the State Board of Health for Michigan (p. 161), six outbreaks are assigned by the medical officers to certain meteorological conditions. One was due to "changeable weather," another to "inclement weather," a third to "exposure to cold," a fourth to "catching cold from home to school," a fifth to "exposure to wet." In these cases the weather

is not to be understood as the specific agent; rather it is one of the prominent conditions that make a given outbreak possible. Raw weather means raw throats, and raw throats are so many traps for the diphtheria bacillus.

2. Soil and Soil-water.-Dr. Monckton Copeman, in the Journal of the Sanitary Institute, April, 1896, summarises the researches of Dr. Thursfield and of Dr. Adams. Soil as a cause of diphtheria outbreaks may operate in three ways: first, by its natural dampness, which may be due to high subsoil water or a prevailing clayey condition; second, by being polluted with decaying refuse, animal or vegetable; third, by leading to dampness in dwellinghouses. (a) "Mr. Adams," says Dr. Copeman, "claims that his records show during the whole period over which they extend a strict concordance between soil-dampness and diphtheria on the one hand, and absence of diphtheria and soil-dryness on the other hand-the disease reaching its acme of virulence when stagnation of the subsoil water is most complete. He contends, moreover, that his observations further demonstrate the fact that the quality as well as the quantity of the disease varies in obedience to the circumstances concerning the subsoil water-there being an agreement in the inverse ratio between the case mortality from diphtheria and the range of the movements of the subsoil water" (p. 32).

Mr. Baldwin Latham's researches at Croydon point in the same direction. In a paper read at the International Congress of Hygiene and Demography (1891) Dr. Hewitt, executive officer of the State Board of Health, Minnesota, said—“The earliest records of diphtheria in Minnesota date before 1860, when it appeared in the families of settlers in the valley of our great rivers as a severe and often malignant tonsilitis, with much glandular enlargement and severe systemic disturbance. From the low lands it spread to the high lands, following the border of the forest, and thence to the prairie, till it invaded nearly every inhabited section of the State." (Trans., vol. 1., p. 108.)

(b) Of polluted soils it is easy to get many instances associated with outbreaks. The Michigan report, already quoted, has these "Unaccountable, unless traceable to the low water and decaying vegetation in and along the banks of the Looking-glass river;" "from swamps and standing water;" "swimming in stagnant water."

(c) Of damp dwellings the instances are very numerous. It

may, I think, be taken as proved that, given the presence of the diphtheria bacillus, diphtheria, as an epidemic disease, is likeliest to strike the low-lying, damp districts, the polluted soils and the damp houses. Dr. Gibert of Havre, in an analysis of diphtheria in Havre for the decade 1880-89, confirms these conclusions. "The commune of Gravilles," he says, "was annexed to Havre in 1855, and this was a heavy charge for Havre. It was only little by little, slowly, that the streets could be drained, paved and kept up. For long years the only sewer was the street gutter, and the bed of clay that occupies the subsoil made this particularly moist." As a result diphtheria was very plentiful and very fatal.

3. Absence of Light.-As a result of Professor Ramsay's superb address at Glasgow, the general public ought to begin to believe in the death-effects of light on bacteria. Both in town and country, however, the favorite geranium or begonia and the care of the furniture will, for years to come, combine to rob light of its microbicidal terrors. In towns, moreover, the insane structure of houses almost invariably leaves some important living part in total or partial darkness-stairs, rooms, closets, water-closets. food presses, clothes presses are, often as not, constructed regard less of light. This matter our Dean of Guild Courts might do something to improve; but fashions in architecture are, like tasnions elsewhere, frequently more apt to change than to be changed. It is, of course, difficult to isolate the direct effects of light; but the direct and indirct effects of the want of light are undoubtedly neglect, dirt and a copious domestic undergrowth of animal and vegetable parasites. The diphtheria bacillus will watch its opportunity like the others. It is proper to add that, where other conditions are favorable, the effect of direct sunlight on the diphtheria. bacillus is to shorten its life only by a few days.

4. Accumulations of Refuse.-To call diphtheria a filth disease is only an emphatic way of asserting that frequently it is assignable to no other known cause; but to assert that any accumulation of filth as such, whether infected with the specific bacillus or not, will give rise to diphtheria, is only to reject the bacillary theory as incomplete or wrong. If the bacillary theory is accepted, then to say diphtheria is a filth disease is merely to say that filth forms a good medium for the growth and propagation of the organism outside the human body, and that, when the supply of human diphtheritic bacilli goes done, accumulations of filth will always afford a fresh supply. Common sense indicates that, when the organism is not

growing in a human throat or in a laboratory, it may yet be growing in the well-stocked laboratories of organic nature, which, from the point of view of human living, are filth heaps. It is with qualifications like these that we must accept the assigning of diphtheria outbreaks to a filth origin. And there is another qualification of equal importance. The bacillus of diphtheria is very often associated with other micro-organisms, for example, with the organism that produces pus (or abscesses), streptococcus pyogenes. This effect was first demonstrated by Professor Alexander Ogston, professor of surgery in Aberdeen University. This organism plays perhaps the chief part in many diseases. Dr. Bulloch has recently re-investigated its history, and he finds it must be reckoned with in erysipelas, pseudo-erysipelas, pyaemia, and septicaemia (that is, forms of blood poisoning), puerperal fever in several forms, in a large number of respiratory diseases, in pneumonia, in typhoid fever, in scarlet fever, in diphtheria, in pulmonary tuberculosis, in many diseases of the nervous system, as in meningitis, in many forms of nondiphtheritic sore thoats, in pleurisy, in peritonitis, in nephritis, in smallpox, in forms of acute bowel catarrh, and in other diseases unspecified. That streptococcus should be found in so many connections proves it to be widely spread in the animal and vegetable kingdoms. Probably many cases of apparent diphtheria are really due to streptococcus alone, and the worst forms of diphtheria as a rule are associated with streptococcus. In any case, streptococcus, or forms of organism related to it are almost universally found in filth, and may prepare the human throat for the reception of diphtheria when, in the absence of the filth-organism, the diphtheria bacillus might have floated by harmless and unharmed. Horses are now immunised against streptococcus, and the effects of the serum on certain diseases have been very striking. It seems likely that the study of streptococcus will produce a greater hygienic revolution than the study either of tuberculosis or of diphtheria. One must keep these considerations in view when one reads, in the Michigan reports of 1892 and 1893, that one outbreak was assigned to "living near a manure heap," a second to "filthy condition of house and premises." a third to "decayed vegetable matter," a fourth to "decayed vegetation in a cellar," and so on. Dr. Lennox Browne points out that in nineteen epidemics investigated by the Local Government Board of England "emanations from accumulations of organic and other refuse" were found. These instances refer to accumulations of