248 RAINS AND THE DECAY OF REFUSE MATTER. 



now become exceedingly unhealthy. The plague of 

 flies also begins this of itself is an unhealthy sign* - 

 so that everything combines to impress upon the 

 prudent traveller the necessity of an immediate retreat 

 to some open, healthy situation, until the sickly season 

 has gone by. 



The moment the heavy rains begin to fall, though 

 they usually have the effect of producing a refreshing 

 coolness in the sultry air, fermentation of vegetable 

 refuse is at once set up : dry leaves and other vegetable 

 matter, till then harmless, begin to soften, and rapidly 

 decay. This process is generally accompanied through- 

 out the thick coverts by a sickly corpse-like odour, 

 which then pervades their atmosphere: marking the 

 (to us) detrimental change which is in progress. 



Evil odours may almost always be regarded as 

 Nature's danger signal. Certain scents are disagreeable 

 to us, probably because they are hurtful and unwhole- 

 some. The nose therefore, as we have before observed, 

 may be regarded as "The Sentinel of Health," on 

 account of the sense of smell thus warning us of 

 perils, even as a sentinel is posted to give intelligence 

 of danger near the camp of an army. 



In former days when these things were less well 

 understood than they are now, many lives were lost 

 by persons exposing themselves in jungle tracts at 

 this unhealthy season, when some form of malarial 

 disease of malignant type was but too apt to cut short 

 their travels and their existence at one and the same time. 



The phenomena which mark the advent of the rains, 

 can hardly fail to prove exceedingly impressive to 



* We shall have more to say, presently, respecting flies, as a me- 

 dium of conveying infection and spreading disease. 



