or ATMOSPHERIC CHANGES UPON DISEASE. 169 



•cases, — the diarrlicea agent lias again received a check 

 from which it does not recover. 



Dysentery 



(i) Seems to be influenced by the variations in the mean 

 temperature, but in less degree than- diarrhoea, the 

 effect not being generally traced in the lesser undula- 

 tions of the curve. * 



(2) Increased atmospheric pressure seems to be unfavour- 

 able to the progress of the disease, high readings of 

 the barometer being nearly always accompanied by 

 diminished prevalence of dysentery. 



The dysentery curve rises, on the whole, from the week 

 ending April nth to the week ending September 12th. 

 Fostered by the unusual warmth of the season, the disease 

 seems to gather such strength that for a fortnight after 

 the mean temperature begins to decline, it rushes on to 

 still greater prevalence, and reaches its highest point when 

 the mean temperature has fallen from 68° to 6o*^.° 



The diminishing autumnal temperature, however, seems 

 at length to produce an opposing influence, for the disease 

 from this point gradually subsides, with occasional fluctua- 

 tions, until the week ending January 16th. There is then 

 a sudden temporary rise in the disease curve, the mean 

 temperature being now above the average, but having 

 been very variable in the preceding three weeks. 



During February 1858, there is a rapid increase in the 

 number of cases which is associated with a temperature 

 very much below the average (as though great cold as well 

 as great heat were favourable to the disease) ; but it must 

 be noticed at the same* time that the barometric reading 

 during the month was very low. 



The disease curve now falls until April 17th, and con- 

 tinues low until June igth (nearly the same date as that 



SER. III. VOL. I. z 



