CONDITIONS INFLUENCING PREVALENCE 157 



the greater part of the year, but nevertheless it would 

 not compare very unfavourably with the temperate zone 

 from a health point of view, could we but do away with 

 malaria. While proposing, in the main, to treat the inter- 

 dependence of malaria and Mosquitoes as an established 

 fact, it may be well to devote a few words to certain 

 objections that have lately been, in various forms, advanced. 

 The first is that malaria may exist in places or at seasons 

 when Mosquitoes are rare or absent. Now in the first 

 place, putting aside certain little visited islands, gnats or 

 Mosquitoes are to be found practically everywhere, from 

 Greenland to the Equator, and it may be taken as certain 

 that abundance of these insects or their larvse would be 

 found by any one accustomed to the search in every one 

 of the cited cases of their absence. Moreover, it will be 

 generally found that such objections are raised by persons 

 who, however intelligent and highly educated they may be, 

 have had no practice in observations of the kind required 

 for the record of facts bearing on natural history, and they 

 are apt to forget that, in this, as in any other special 

 business, long training, much patience, and a certain apti- 

 tude, are required for the work. A writer, for example, in 

 a well-known Indian lay journal, a propos this question, 

 gravely propounded the astounding statement that Mos- 

 quitoes were extinct in India in the rains, and specially 

 troublesome in the cold weather, whereas, without for a 

 moment questioning the good faith of the writer, it is 

 needless to say that exactly the reverse is the case. In all 

 probability he had never made a single definite note on the 

 subject, or troubled himself as to whether few or many 

 Mosquitoes were about, since the time when they made 

 themselves painfully obvious to the newly landed journalist 

 during the time he was acquiring that indifference to their 

 bites which all of us sooner or later develop ; and under 

 such circumstances memory is naturally treacherous. 



Another argument that has been used is that, whereas 

 the presence of malaria is dependent on that of man, and 

 should therefore be worst where population is thickest, the 

 reverse is the case, as towns enjoy a practical immunity. 



