OF ATMOSPHERIC CHANGES UPON DISEASE. 179 



From June ijth until October o^rd the temperature re- 

 mains high (above the forty-three years^ average nearly 

 every week), and during this time the disease is at its 

 minimum (between forty and fifty cases per week). 



The number of cases does not again increase until the 

 sudden fall of temperature in October and November^ after 

 which the weekly average remains pretty constant until 

 February s.<^th, unaffected by the great fall of temperature 

 in 'the week ending January ^th 18^8, but it again rises 

 rapidly after the extreme cold of February and March 

 (which was much below the forty-three years average). 



It remains very prevalent during the spring of 18^8, 

 but the remarkably warm June appears to check its pro- 

 gress, just as it did in the preceding year. 



It is important also to notice that an increase in the 

 number of cases again takes place in July, the temperature 

 being much below the average ; the year before the curve 

 declined much more regularly and continuously. 



Durmg the summer of 1858 the disease remains almost 

 stationary, as in the preceding year ; but while it may be 

 observed that the temperature is never so high as then, 

 the number of cases never sinks so low (seldom below 

 sixty).* 



Scarlatina. 



A large amount of aqueous vapour in the air appears 

 greatly to facilitate the formation and action of the 

 peculiar scarlatinal poison, especially when this is 

 accompanied by sudden fluctuations in the atmo- 

 spheric pressure as shown by the barometer; a 

 diminished pressure being favourable to the disease. 



It is rather difficult to separate the influence of tempera- 



* Drs. Donnelly and Wilde remark that spring affords rather more than 

 the average amount of small pox, measles, scarlatina, and whooping cough. 

 Census of Ireland for \%$\. 



