OF ATMOSPHERIC CHANGES UPON DISEASE. 177 



wliile the temperature falls, and it continues to rise until 

 November ///*, and then falls until November 215^, as 

 though checked for a time by the temporary rise in the 

 temperature of the preceding week (when it is 8° above 

 the average). The disease attains its maximum in the 

 week ending March 13^^,* the temperature having reached 

 its lowest point in the week preceding, and being more- 

 over 7'^° below the average. 



The temperature now rises, and the disease diminishes 

 in prevalence during the month of April : the week ending 

 April 10th alone has a temperature below the average, and 

 the number of cases again slightly increases for that on^ 

 week. 



During the month of May the disease increases in pre- 

 valence, although accompanied by an advancing tempera- 

 ture which, however, is below the average; but after the 

 week ending June gth, which has a mean temperature no 

 less than 10° above the average, the disease curve gradually 

 declines until July 10th. The temperature in the week 

 ending July 10th sinks to 56° (6° below the average), and 

 from July 24//* to August jth it is 2'^° below the average; 

 and in all these instances a slight rise in the number of 

 cases follows. With these exceptions, however, the disease 

 curve rapidly declines until the week ending October 2nd; 

 this week the temperature sinks to 51° (slightly below the 

 average), and the depression is immediately succeeded by 

 a rapid increase in the number of cases.f 



Comparisons of the daily mean barometer readings, 

 during the period April 18^7 to October 1858, tend to 

 show that during the time this disease was most prevalent 



* " They begin as soon as January ; they increase gradually ; they reach 

 their height about the i^th of March ; they then gradually decline, so that, 

 with the exception of a few tliat may attack isolated individuals, they dis- 

 appear by midsummer." — Sydenham, Med. Obs. i. 3. 



t Dr. Miihry states that measles in the temperate zone experiences mffl 

 change with the temperature. 



SER. III. VOL. I. A A 



