CHOLERA. 



511 



Table I. 

 Average Frequency of Cholera^ and Average Rainfall {in Inches) in Calcutta. 



(March and April), and its minimum is attained during the wettest and 

 hot month of August, so that the curve of cholera falls while that of 

 rain rises. The rise and fall of endemic cholera is constant, while the 

 prevalence of cholera in its epidemic form is very variable. In the 

 Punjaub the rain-winds (monsoons) bring with them the cholera. This 

 apparent contradiction of the experience above mentioned may be ex- 

 plained by considering that the monsoons bring to the Punjaub the 

 necessary moisture which is believed to be requisite for the develop- 

 ment of an epidemic of cholera. Rain falls in the Punjaub at the 

 same time as in Lower Bengal, but in smaller quantity. The average 

 rainfall at Lahore is twenty-two inches, as compared with sixty-two 

 inches at Calcutta ; so that in Lahore for the greatest part of the year 

 the soil is too dry for cholera. That these claims are substantial will 

 be granted by a study of the rainfall and related circumstances in 

 other parts of India. This is well seen at Madras, as indicated by 

 Table II. At Madras the average rainfall is about forty-eight inches, 



Table II. 

 Average Frequency of Cholera^ and Average Rainfall (in Inches) in Madras. 



and is therefore midway between those of Lahore (twenty-two inches) 

 and Calcutta (sixty-two inches), but the quantity of rain in the several 

 months is different. The greatest quantity of rain falls in November, 

 and Madras is not under the influence of the southwest, but of the 

 northeast monsoon, and the rainy season extends from July to Decem- 

 ber. As Madras lies farther south than Calcutta, and the quantity of 

 rain is twenty-five per cent less, it is plain that the desiccation during 

 the dry and hot season would be much greater there than in Calcutta. 

 And this state of affairs is reflected in the vegetation. April, May, 

 and June are like winter months ; the leaves begin to fall ; the verd- 

 ure fades away, and the sap descends to the roots of the trees, not 

 because of the cold, but on account of the excessive dryness. It is at 

 this period that cholera is at its minimum. In July, when the rain 

 begins to fall, cholera increases, and reaches it maximum in August. 

 The rain continues, but the cholera decreases, owing to the excessive 

 dampness of the soil ; so that in November a second minimum in the 

 number of cases of cholera is met with. 



