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VII

week, the same rate of mortality. This, as the nearest approach both to the prevalence and intensity of the disorder at fixed times, afforded the means of measuring a standard of the disease by a standard of the meteorological states presented during the same times. I found, then, twelve weeks, viz., the weeks ending January 17th and April 4th, 1846 ; January the 2nd, April the 10th, June the 19th, July the 3rd and 31st, and August the 7th and 14th, 1847; and January 11th, February 1st, and March 15th, 1851 ; in all of which the mortality from scarlet fever was sixteen cases per week. I found five other weeks, viz., the weeks ending November the 2nd, 1850; September the 20th and 27th, and December the 20th, 1851; and January the 3rd, 1852; in each of which the mortality was forty-one per week. And finally, I selected two weeks, the one of extremely high, the other of extremely low mortality. The week ending October 14th, 1848, represented the first of these, for in this week there were one hundred and eighty-eight deaths; the week ending April the 18th, 1851, represented the second of these, there being only eight cases recorded.

Analysing these cases of death, and subjecting them to careful study by the side of the meteorological conditions, I constructed a table, of which the following is an abstract.

In the twelve weeks in which the mortality was sixteen per week, the mean temperature varied as much as 36°; one of the weeks having a mean of 65°, another of 29o. In the five weeks in which the deaths each

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week were forty-one, the range of temperature was from 36 to 57°, giving a difference of 21°. In the week when the mortality was extremely high, viz., one hundred and eighty-eight, the temperature was 52 ; whilst in that week in which the mortality was so low as eight, the mean temperature was 46o.

Turning from the thermometer to the barometer, I found an equal want of relationship. In the twelve weeks where there was an equal mortality per week of sixteen, there was a range in the barometrical readings varying from 30-277 to 29-435, or 0.842. In the weeks in which the mortality was forty-one, the reading varied from 30.190 to 29.625. In the week with the high mortality, one hundred and eighty-eight, the mean barometrical reading was 29.824; while in the week with the low mortality, eight, the reading was 29.776.

The Amount of Rain. In the twelve weeks of equal mortality of sixteen, the extremes were 1.61 to 0:00. In the five weeks in which the mortality was fortyone, the rain fall was 0.15 to 0:00. In the week of the high mortality, one hundred and eighty-eight, the fall was 3.42; and in the week of the low mortality, cight, it was 0.02.

The Rate of Atmospheric Movement. In the weeks of equal mortality of sixteen per week, the difference was most varied; in one week there was absolute calm, in another the atmospheric movement had a mean of 207.857 miles per day. In the weeks with an equal mortality of forty-one, the range of atmospherio motion was from 428 to 975 miles per week. In the week of very high mortality, one hundred and eighty-eight, the rate of motion of the air was 1,010 miles; and in the week of low mortality, eight, the movement was only 590 miles.

The Electrical Conditions of the Atmosphere showed a somewhat nearer approach towards one rule. In the twelve weeks, or eighty-four days, of equal mortality of sixteen, there were not less than fifty-seven days in which the electricity was positive; only three days in which there was negative electricity all the day; five days in which positive and negative electricity were shown on each day at different periods; and nineteen days in which the electrical results were nil. In the five weeks, or thirty-five days, in which the mortality was forty-one per week, there were three days and two hours of positive electricity; no evidence of negative electricity; but thirty-two days, minus two hours, in which no electrical results were given. In the week in which the mortality was one hundred and eighty-eight, positive electricity was developed on two days, negative on one day, and on four days none; while in the week of lowest mortality, eight, the electricity was positive on two days, and absent on five days.

From these records we can deduce, as I have already premised, but few facts of value bearing on the effects of special atmospherical changes on scarlet fever. It is worthy of remark, certainly, that during the period of eighty-four days when there was an equal weekly mortality of sixteen, there were fiftyseven days of positive electricity; while in the thirtyfive days, during which the mortality was at the rate of forty-one per week, there were thirty-two days in which there was no electrical manifestation. It might be inferred, hereupon, that the absence of electrical manifestation was connected with a high mortality, and, on the contrary, that the presence of positive electricity was connected with a low mortality. But when we see again a week of extreme high mortality, one hundred and eighty-eight, during which we have two days of positive electricity, and a week of extreme low mortality, eight, during which electricity was absent on five days, we can but accept the facts which seem to have an affirmative meaning in the light of mere coincidences. Yet it may be, that in the future some relationship between the presence of electricity and a low mortality from scarlet fever will be traced; for it is possible that, while electricity in no way interferes with the spread of the contagion of this disease, it produces modification in the effects of the poison on the animal organism.

But if there be only this one finger pointing affirmatively towards the relationship of meteorological conditions and scarlet fever, there is a large amount of negative evidence supplied in the statistics I have given. We see, for example, that, with equal mortality, the most opposite conditions of temperature may be presented; but the most interesting observation is that in reference to the movement of the air. Assuming that the disorder were propagated by means of a volatile poison, it is obvious that such poison is limited

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in its range of action, or, at all events, that it is not influenced, by the mechanical vibrations of the atmospheric sea. In a dead calm the mortality may in one week be sixteen; and in another week, with a current of air passing over the infected spot at the rate of fourteen hundred and fifty-five miles per week, or two hundred and seven miles per day, the mortality shall be the same; while again with a week of extraordinary high mortality, one hundred and eighty-eight, a current of air may be sweeping over the home of the disease at the rate of one thousand and ten miles per week.

I know how many objections may be brought to bear on the method, laborious though it has been, by which the above considerations have been arrived at. It may be urged that mortality is not a sure indication of the prevalence of an epidemic; it may be urged that the meteorological conditions which attend the fatal end of a disorder are not necessarily the same as those which were present when the disorder was being communicated. And these objections are so valid that I would not dispute them. My sole object is carried out now, if I have indicated all that can be gathered from the best and only resources we at this present have at command.

The Recurrence of Scarlet Fever in the same Person is an interesting fact, and one that deserves to be made a subject of special study. On the possibility of such recurrence, opinion has been divided. The well-known assertion of Willan, that out of two thousand cases of the disease, he had never met with

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