OF ATMOSPHERIC CHANGES UPON DISEASE. 183 



the average), while the degree of humidity continues to 

 rise. 



From this time, however, until October i6th, the hu- 

 midity again appears to exert its influence, and the curves 

 are in accordance. 



The disease curve reaches its highest point for the year 

 (200 cases) in the week ending October i6th, the degree 

 of humidity rising rapidly until October 2'^rd, but the 

 temperature not descending much, and remaining 2° above 

 the average. 



It is interesting to observe the manner in which the 

 curve of scarlatina supplements the curves of whooping 

 cough and measles. "Thus they vex humanity by turns, 

 as the constitution of the year and the sensible tempera- 

 ture of the air most assist the one or the other." — 

 Sydenham.* 



In the foregoing examination into the efiects of the 

 several meteorological elements upon scarlatina, it will be 

 seen that we have ascribed to humidity the chief influence, 

 but at the same time have carefully noted the efiects of 

 variations of temperature and pressure of the atmosphere ; 

 but it may be that we have not sufiiciently indicated the 

 reasons for our opinion. 



"^^^ithout very close comparison it would be very diffi- 

 cult to decide whether temperature or humidity had the 

 greatest influence upon this disease. First, if we take the 

 correspondence of the curves during the same times, we 

 shall find that in 64 per cent of the weekly periods the 

 number of cases rose and fell with the fall and rise of the 

 thermometer, and in 63 per cent with the rise and fall of 

 the degree of humidity; in 42 per cent of the periods 



* Sydenham states that scarlet fever may appear at any season, but 

 oftenest towards the end of summer. — Med. Obs. vi. 2, i. He also speaks 

 of one epidemic being driven out by another " ut clavum a clavo." — Med. 

 Obs. ix. I, 7. 



